Technical Paper 313 AD A

RETENTION OF MOTOR SKILLS: REVIEW

J.D. Schendel, J.L Shields,

S~and ,

M.S. Katz P

0I0

L~j .INDIVIDUAL TRAINING & SKILL EVALUATION TECHNICAL AREA

C.,3

U. S. Army

Research Institute for the Behavioral and Social Sciences

September 1978 j

A

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Technical Paper 313

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TENTION OF MOTOR SKILLS4 REVIEW p Literature review

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J. D. Schendel, J. L. Shields,-Afi. S.)Katz

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I9. KCY WORDS (Continue, on revetre side If necesariy and Identify by block number)

Retention of skills Military training

Motor memory Training transfer

Refresher training Maintenance of proficiency

Forgetting Training research

20. ABSTRACT (Continue an reverse side If nee'•sey end Identlfy br block miter)

"fl A summary of an extensive literature survey deals with the variables known

or suspected to affect the retention of learned motor behaviors over lengthy

no-practice intervals.. Emphasis was given to research conducted by or for the

military. The variables that may affect the retention of motor skills were

dichotomized into task variables and procedural variables. The task variables

that may underlie the long-term retention of motor skill include (a) duration

of the no-practice period, or retention interval; (b) nature of the response

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equired to accomplish a particular motor task; (c) degree to which the learner

can organize or impose order upon the elements that define the task; (d) structure of the training environment; and (e) initial or "natural" ability of the

flearner in performance of a task without prior practice.

The procedural variables that may affect the long-term retention of motor

skill include (a) degree of proficiency attained by the learner during initial

training; (b) amount and kind of refresher training; (c) transfer of skills on

one task to performance on another task; (d) presence of interfering activities;

(e) distribution of practice during training; (f) use of part-task versus wl"ie.

n:ask training methods; and (g) introduction of extra test trials prior to final

testin

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Technical Paper 313

RETENTION OF MOTOR SKILLS: REVIEW

J.D. Schandel, J.L. Shields,

and

M.S. Katz

INDIVIDUAL TRAINING & SKILL EVALUATION TECHNICAL AREA

Submitted as complete and Approved By: technically accurate, by: Milton S. Katz E. Ralph Dusek, Director

Technical Area Chief INDIVIDUALTRAINING AND PERFORMANCE

RESEARCH LABORATORY

Joseph Zeldner

TECHNICAL DIRECTOR (DESIGNATE)

U.S. ARMY RESEARCH INSTITUTE FOR THE BEHAVIORAL AND SOCIAL SCIENCES

5001 Eisenhower Avenue, Alexandria, Virginia 22333

Office, Deputy Chief of Staff for Personnel

Department of the Army

September 1978

Army Project Number Perfnrmance-Based Training 20162722A777

Approwd for public rWlOeOS; distributlon unlimited,

S.....•,.j=•
ARI Research Reports and Technical Papers are intended for sponsors of

R&D tasks and other research and military agencies. Any findings ready for

implementation at the time of publication are presented in the latter part of

the Brief. Upon completion of a major phase of the task, formal recommendations for official action normally are conveyed to appropriate military

agencies by briefing or Disposition Form.

Ail

.3

I

: 44. -
FOREWORD _________________

The Individual Training and Skill Evaluation Technical Area of the

Army Research Institute for the Behavioral and Social Sciences (ARI) has

actively pursued a program of research in support of the systems engineering of training. A major focus of this research is to develop the

fundamental data and technology necessary to field integrated systems

for improving individual job performance. Such systems include Skill

Qualification Testing (SQT), job performance aids, training courses in

schools and in the field, performance criteria, and management and feedback systems. This report summarizes the first step in the development

L of methods to assess and enhance the retention of job skills. This

research is in response to the question, from the Army Training and

Doctrine Command (TRADOC), "What is the required frequency of refresher

training to maintain performance proficiency?" Work was accomplished

by ARI personnel, under Army Project 2QI62722A777, •Y 1978, "Individual

Training Technology." Comments and editorial assistance were provided

by Mr. J. Douglas Dressel and Dr. Joseph D. Hagman.

Snical Director (Designate)

4

4
RETENTION OF MOTOR SKILLS: REVIEW

BRIEF

Requirement:

As part of a major program on individual training for combat

ness, to develop a sound information base for Army decisions necessary

to insure soldiers' long-term skill proficiency, this review focuses on

retention of motor skills.

Procedure:

This review is based upon a wide variety of data from an extensive

literature survey of pertinent research. Although military-related findings were incorporated wherever possible, some of the experiments

cited used tasks having little direct or obvious relationship with

skills currently maintained within the Army. In addition, conflicting

data and data pertinent to a more detailed understanding of the behav- ioral consequences of an extended no-practice period generally were

skimmed over to lend coherence to this report. In so doing, an oversimplified picture of long-term motor memory and the variables that may

affect it has been sketched. These constraints notwithstanding, a number of tentative conclusions have empirical support.

Findings:

1. The single most important determinant of motor retention is

level of original learning. Knowledge of results and response-produced

feedback are thought to contribute most to a trainee's original learning. Effectiveness of the knowledge of results increases with its availability and precision. Effectiveness of response-produced feedback increases

with its quantity, for example, number of feedback channels and amount of

practice, and fidelity.

2. Procedural tasks are forgotten in days, weeks, or months,

Viereas continuous control tasks typically are remembered foz months or

years.

3. Retention of skill decrease3 with time, depending on a host of

variables, including the length of the no-practice period, the type of

task, and the practice or interfertng activities before or during the

retention interval.
4. Retention is improved by increasing the amount of original practice. Overtraining or mastery training may be more cost effective than

proficiency training, that is, training to one successful performance.

5. Time to retrain individuals to original performance levels is

generally rapid, consistently less than half the original training time.

6. Learners apparently can impose organization upon psychologically

unstructured tasks via the learning process. As a result, task structure

is not an important variable for the long-term retention of well-learned

responses, although it is an impo-tant variable for the retention of less

well-learned responses.

7. Functional similv-ity of the training device to the actual

equipment is a necessary and sufficient condition for learning procedural

tasks.

8. Display-control relationships can influence the ease of motor

learning e.nd transfer and, to some degree, the quality of performance

after a retention interval.

9. ;..gmented feedback can enhance performance by raising motivation,

learning, or both.

10. Individual ability levels are important as determinants of

retention insofar as they influence a person's time to achieve a standard

level of performance. Individuals of higher initial ability tend to

achieve higher levels of proficiency and retain skill at a higher level

than individuals of lower initial ability.

11. Refresher training can serve as an effective source of new

learning as well as a means for reestablishing forgotten responses. It

also may provide a relatively simple means of improving on-the-job

safety and performance.

12. Learning and retention are benefited by test-taking

opportunities.

13. Positive transfer effects typically are observed when transferrin; between motor tasks. Although negati, transfer is the exception,

occasional intrusive wrong responses inducea by past learning may have

serious consequences for operators or equipment.

Utilization of Findings:

The conclusions and implications of previous research provide a firm

basis for specific, ongoing programs to develop procedures that the Army

can use to insure that its personnel remain job proficient over prolonged

periods.
3- N. AN M

RETENTION OF MOTOR SKILLS: REVIEWb

CONTENTS

Page

IN4TFODUCTION .. ...................................................... 1 2

Purpose dnd Scope................... . . . ... . . .. .. .. .. ........

Aýpproach....................... .. . . ...... . ;. ..... .. ........

RETENTIION 0;'MOTOR SKILL: REVIEW. .................................. 2

Thlsk Variables. ....................................................

Aitention Interval .. .......................................... 2

1w*ttore of the Response .. ...................................... 4

organization .. ................................................ 6

Training~ Environment .. ........................................ 7

Individual Ability Levels .. .. ................................ 11

Procedural variables .. .... ...................................... 12

Level of Original Learnin . .. ................................ 12

Refresher Training. .. ........................................ 16

Transfer of Training. .. ...................................... 18

Trace Decay and Interference. .. ...................... . . 18

Schedules of Practice .. ...................................... 194

rWhole- Versus Part-Training Methods .. ...... .................. 20 Additional Test Trials. .. .................................... 22

SUMMARY .. .......................................................... 23

CONCLUSIONS .. ...................................................... 25

REFERENCES. .. ...................................................... 27 4

DISTRIBUTION. .. .................................................... 39

LIST OF FIGURES

Figure 1. Hypothetical forgetting curve .. .......................... 3

2. Hypothetical performance data for two groups trained

with and without augmented feedback and then transferred

to common conditions after a rest interval .... .......... 10

3. Hypothetical forgetting functions for three groups of

varying initial ability. .. .............................. 13
RETENTION OF MOTOR SKILLS: REVIEW

INTRODUCTION

The mission of the U.S. Army during peacetime is to maintain a state

of readiness to fight and to win the first land battle in event of war

(39).* To accomplish this mission, Army personnel must be equipped with

state-of-the-art weaponry and kept proficient in its use. Opportunities

for sufficient post-mobilization training after the onset of war are not

expected.

Establishing training procedures to develop proficient trainees is

one problem; providing guidelines to maintain each individual's proficiency is another. These problems are interrelated and magnified by a

resource-constrained environment. Cost-effective training demands that

the Army identify procedures that enhance proficiency and minimize an individual's requirement for "refresher" training.

Purpose and Scope

This review seeks to develop a sound information base to facilitate

Army decisions about training, transferring, and maintaining (i.e., longterm retention) skills that are critical for combat readiness. An information base would allow the Army to (a) develop procedures to maintain an

individual's proficiency over prolonged no-practice periods, for example,

weeks, months, or years; and (b) establish more accurately the optimal

intervals for many refresher training programs.

The focus of this review is on the long-term retention of motor behaviors because well-learned, well-maintained motor behaviors (such as

those involved in operating a tank, piloting an aircraft, shooting a

rifle, or launching a missile) are necessary to achieve a guaranteedeffective retaliatory strike force. Of course, the findings are equally pertinent to the retention of less dramatic skills that are just as im- ii

portant for maintaining an effective Army.

Approach

This report presents a summary of an extensive literature survey

dealing with the variables known or suspected to affect the retention of

learned motor behaviors over lengthy no-practice intervals. The survey

was accomplished using major documentation sources (i.e., Defense

*Numbers in parenthesis refer to specific report citations in the

References section.

1 ;1
Documentation Center, Human Resources Research Organizeaton library,

National Technical Information Service), data bases (Aitomated Data on

Instructional Technology, Educational Resources Information Center,

Psychological Abstracts), and a followup search of the psychological,

military, and business/industrial literatures.

Research conducted by or for the military using military personnel

as experimental participants was emphasized. Special consideration was

given to research that employed evidently military-relevant tasks. Research on tasks having few real-world applications was included only if

the results were practically indicative or suggestive.

RETENTION OF MOTOR SKILL: REVIEW

The variables that may affect the long-term retention of skilled

motor performances were dichotomized into task variables and procedural

variables. Task variables relate to the trainee or to the training/test

environment, whereas procedural variables relate to the manner in which

training, final testing, or both occur. Conclusions drawn about each are

underscored in the text, with important reservations and exceptions noted.

Directions for future research are suggested where the literature relating

to the effect of a particular experimental manipulation is ambiguous.

The task variables that may underlie the long-term retention of motor

skill include (a) duration of the no-practice period, or retention interval; (b) nature of the response required to accomplish a particular motor

task; (c) degree to which the learner can organize or impose order upon

the elements that define the task; Wd) structure of the training environment; and (e) initial or "natural" ability of the learner to perform a

task in the absence of prior practice.

The procedural variables that may affect the long-term retention of

motor skill include (a) degree of proficiency attained by the learner

during initial training; (b) amount and kind of refresher training;

(c) transfer of skills from one task to another task; (d) interfering

activities; (e) scheduling of practice during training; (f) use of parttask versus whole-task training methods; and (g) introduction of extra

test trials prior to final testing.

Task Variables

Retention Interval

The retention interval is the period of no practice between the

acquisition and subsequent test of a performance. The classical curve of

foErgcttirs,, as depicted in Figure 1, is believed to apply to motor

responsos.

2
1.0

o - I I

Length ef Retentiin, Interval

4-4

Figure 1. Hypothetical forgetting curve.

3

, . 3
Note that the absolute amount f:rgotten increases ;ith time, whereas

the apparent rate of forgetting declines with time. Of course, the exact

shape of any forgetting curve depends upon a host of variables (21) including (a) the amount of practice the learner receives (48,72); (b) the

length of the interval between training and retention measurement (129);

(c) the nature of the response to be retained (14); and (d) acZivities

that interfere with acquisition or retention (75).

Nature of the Response

Motor responses are classified typically as either continuous or

discrete, but probably no response is totally one or the other. We will

define pattern a response as Sment continuous if it involves the repetition of a move- that does not have a discernible beginning or end. The most _k

commonly employed continuous task in studies of motor 1remory is tracking,

presumably because it is the response activity that underlies vehicular

control (2).

There are two types of tracking tasks, pursuit tracking and compen- 1

satory tracking. In pursuit tracking, the operator can see both the target to be followed and his tracking device or cursor. The operator's job

is to keep the cursor aligned with the target so that the discrepancy between the two is nullified. Keeping a weapon sight (cursor) on a moving

tank (target) is an example of a pursuit tracking task. In compensatory

tracking, on the other hand, neither the target nor its position is displayed. The operator knows only the difference between an errorindicator and a fixed reference, and his task is to nullify this

difference.

For example, error-nullifying principles are the basis of certain

navigational instruments that signal the operator to begin directional

(or attitudinal) corrections if he strays off the intended course. Also,

the "leveling vials" used in field artillery may be regarded as a kind of

compensatory tracking device. By compensating for the movement of an air

bubble (error-indicator) floating within a glass tube mounted on the artillery piece, the gunner can adjust the artillery piece to a horizontal

plane. -)

A response is discrete if it has a definite beginning and end and,

typically, is quite brief in duration, for example, less than 5 seconds

(117). Familiar examples of discrete responses include moving a gear- _

shift, shooting a rifle, or throwing a hand grenade. Procedural tasks

typically are composed of a series of discrete motor responses. Usually,

the learner's main problem on each trial is selecting the correct response

from a repertoire of possible responses rather than actually executing the

response. The learner's main problem is determining "what to do" rather

than learning "how to do it," for example, reassembling a carburetor or

operating a radio communications system.

4
This need not always be the case, however, because certain procedural tasks such as playing the piano or executing the Manual of Arms

not only require the performer to learn to select an appropriate series

of responses but to learn how to execute them with the proper force and

in the proper time sequen'ce as well.

Procedural tasks and individual discrete motor responses are forgotten over retention intervals measured in terms of days, weeks, or

months, whereas continuous movements typically show little or no forcetting over retention intervals measured in terms of months or years

Although support for chis proposition has been obtained in a wide variety of basic (129) and applied research settings, the most notable contributions have been made by investigators concerned with the long-term

retention of piloting skills (51,99,100,127). Studies dealing with the A

maintenance of instrument flying skills (9,87), manned spacecraft flight

operations (123,124,125), and l.unar landing skills (38) consistently

indicate that important procedural aspects of flight control deteriorate

to unacceptable or unsafe levels over retention intervals measured in

terms of weeks or months.

All-hough data are lacking with respect to the maintenance of Army

job-relevant procedures, data on the maintenance of basic combat training skills (83,141), the preparation and firing of a Nike-Hercules missile (54,55), and gunnery proficiency in a combat air force (World War II)

(114) support the contention that procedural proficiency cannot be maintained in the absence of regular practice.

Data on the retention of continuous movements come from studies of i

pursuit tracking (19,64,71,103,115,126), compensatory tracking (9,14,

18,48,87), and balancing (88,101,109,115). In contrast to the findings

for procedural tasks, continuous movements generally are retained well

over prolonged retention intervals, even in the absence of practice.

For example, researchers, using a part-task flight simulator, found a

95% loss of procedural response proficiency over a 10-month retention

interval, but found no effect upon the retention of continuous flight

control responses (9). Others concluded that, although the forgetting of

cockpit procedures over a 4-month retention interval could impair a pilot's flying efficiency and safety, this interval was not sufficient to

degrade a pilot's continuous motor aircraft-control skills (87).

A number of hypotheses have been offered to account for the difference in retention of procedural and continuous movement tasks (2,92,129).

They are as follows:

1. The verbal-cognitive nature of procedural tasks may make them

easier to forget than continuous motor responses.

2. It is unclear what constitutes an individual trial iuring a

continuous performance and, as a result, continuous responses

may be overlearned and thus retained better than discrete motor

responses.

5

- b 
3. Continuous responses may be retained better simply because they

are more integrated or coherent than procedural tasks.

4. Retention differences between tasks may be partially due to the

way errors are scored, that is, the methods used to score the

retention of discrete motor responses may be relatively more

sensitive to slight performance deviations than the methods used

to index the retention of continuous responses.

Regardless of which interpretation finds support, the observation

that procedural tasks are less likely to be retained at an acceptable

level over a retention interval than are continuous responses has implications for Army training. In particular, regular refresher training

must be provided for tasks that emphasize procedural knowledge. A similar recommendation was made to the Navy after a study was conducted on the

forgetting of procedural and continuous instrument flying behaviors (87).

Fortunately, procedural tasks are typically less expensive and simpler to

train than are continuous responses because procedural tasks require little in terms of equipment beyond simple classroom training aids (54,55).

Also, it is known that verbal cues and written job aids can facilitate

the training and maintenance of procedural tasks (61,81). Techniques

based upon this observation currently enhance on-the-job performance in

the Army (the Integrated Technical Documentation and Training Program).

Research efforts to make written job aids more accessible and easier to

understand are likely to yield additional performance benefits.

Organization

Organization refers to the process by which the learner imposes

order or structure upon the elements that define his task by establi..hing consistent relations among them (52). Evidence within the verbal

(137) and nm-tor (98,131,134,135) memory literatures suggests that tasks

inherently amenable tcý Learner organization are learned at a faster rate

than less structured tdsks. Under conditions of moderate learning, highly

structured tasks also are retained at a higher level than less structured

tasks. Once learning reaches an advanced stage, however, individuals

apparently can retain less structured tasks as proficiently as highly

structured ones.

For example, groups of individuals in one study were trained to perform two tasks simultaneously. The primary task was compensatory tracking, and the secondary task involved learning either a highly structured

or less structured procedural sequence. Training was conducted for either 2 or 3 weeks and was followed by retention testing after either 1 or

4 weeks. As predicted, retention of the primary and secondary tasks by

groups having the highly structured secondary task was superior to that

of groups having the less structured secondary task. This effect,

however, held only for those groups receiving moderate amounts of training. The structure of the secondary task did not affect the loss of

tracking or procedural proficiency under greater amounts of training (94).

6
Thus, individuals apparently can impose structure upon psychologically unstructured tasks by organizing, but the act of organization

takes time and practice. Indeed, the amount of time and practice required for a learner to organize some tasks may be too long for any

reasonable training period. If sufficient initial learning opportunities exist, however, less structured tasks can be retained as well as

highly structured ones.

Training Environment

A number of environmental variables have been identified (51) that

may affect the long-term retention of military-related tasks. Among the

variables are (a) the fidelity of training devices; (b) the compatibility

of display-control relationships, (c) the specificity of task displays;

and (d) augmented feedback.

Fidelity. The similarity between training devices and operational

equipment can be viewed from two perspectives: physical similarity and

functional similarity. Physical similarity, or fidelity, refers to the

physical resemblance, in an engineering sense, between the displays and

controls on a training device and those on the operational equipment.

Functional similarity, on the other hand, refers to the "degree of representativeness" or "psychological realism" of a training device relative

to the actual equipment (145).

Functional similarity is a necessary and sufficient condition for

learning procedural tasks. For illustration, the acquisition and longterm retention of a 92-step proceduial task (firing a Nike-Hercules

missile) following training on a high-functional similarity drawing of

the operational equipment has been shown to equal learning and retention

following training on the actual equipment (54,55). A similar result

was obtained using a complex procedural communication task (20). A

comprehensive overview of the variables influencing transfer from training device to operational setting has been provided elsewhere (144,145).

Display-Control Compatibility. Certain display-control relationships appear to be more "natural" or "expected" for the human operator

than others. This notion is based upon the observation that when several

display-control relationships are possible for a given eye-hand coordination task, one relationship will lead to substantially better initial

performance than the others (46). The itterpretations offered for this

effect suggest that compatible display-control relationships are more

consistent with the learners' past'-experiences with the environment

(1,120) or perhaps more consistent with the principles of human biomechanics than incompatible display-control relationships.

6 *1l
Examples of display-control relationships that typify those normally

encountered in the environment include (a) moving a pointer to the right

(display) by moving a lever to the right (control); (b) moving a pointer

to the right by rotating a knob in a clockwise direction; and (c) moving

a pointer downward by moving a lever forward (86).

The compatibility of diaplay-control relationships influences the

ease of motor learninq and transfer (1,29,46) as well as the quality of

performance after a retention interval (86). These results have implications for training and equipment design. Individuals training on highcompatibility equipment require less training to achieve and to maintain

a satisfactory level of performance than individuals training on equipment

having incompatible display-control relationships.

Indeed, it is suggested that the performance of individuals afforded

a reasonable amount of training on equipment having incompatible displaycontrol relationships may never catch up to the performance of individuals

using high-compatibility equipment (46). The compatibility of displaycontrol relationships may not pose serious problems during the performance

of slow, self-paced tasks that allow a liberal margin for error. But it

would be a mistake to expect optimal performance using equipment with incompatible display-control relationships in potentially dangerous (120),

externally paced, or infrequently performed tasks.

Specificity of Task Displays. Most tasks, such as tracking, depend

heavily upon the processing of visual information from a task display.

At least during the initial stages of learning, the learner is forced to

rely upon the visual cues he receives from the task display to guide his

performance. Later in learning, however, the learner relies more on proprioceptive or other internal sources of information and depends less on

the display and other external cues (16,49). This suggests that visual

cues designed to supplement the information provided by the task display

are informative early in learning and facilitate the learning process,

but may be relatively uninformative once the learner has "internalized"

the performance. This hypothesis was tested using a pursuit tracking task

and task displays that varied in "specificity." Display specificity involved a numerical code and/or several grid systems that, superimposed on

the face of an oscilloscope, permitted several levels of target-location

cueing (136).

As predicted, the early acquisition of the tracking task was facili-,

tated under conditions of high-display specificity. However, the specificity of the display did not affect the final levels of skill attained

by the learners nor the 1-month retention. Apparently, later in learning,

supplementary cues from a display do not provide information over and

above that which is already provided by internal sources and consequently

are not important as determiners of retention.

8 7
41

Augmented Feedback. Information about a response may be augmented,

or supplemented, by delivering general instructions or perceptual cues to

the trainee before, during, or after the response. For example, if the

trainee can see each time he scores "a hit" on the standard task, then

saying "hit" or flashing a light augments feedback. Little has been done

to assess directly the effects of augmented feedback on the long-term

retention of motor responses. The only experiment found on the subject

failed to find any effect of supplementary auditory noise upon the acquisition or retention of a compensatory tracking task (33).

The effects of augmented feedback vary from task to task, both while

the extra feedback is present and in tests after it has been removed (25).

When augmented feedback is present, it often facilitates performance during training (29). This facilitation has been attributed to changes in

motivation (22), learning (102), or both (69). To understand how these

interpretations differ, see Figure 2. The figure presents the hypothetical performance data for two groups trained with and without augmented

feedback that were transferred, or shifted, to common conditions after a

R rest interval. The three possible outcomes of the transfer test are illustrated in A, B, and C (117), and are explained below.

Certain variables, such as motivating instructions (47), stimulate

or activate the learner to perform previously learned responses more

vigorously, but they have no direct effect on the strength of those

responses in memory. A variable that raises or lowers performance when

present and whose effects disappear rapidly when removed is called a

K performance variable (result A).

For example, one experiment (22) involved the acquisition of an ele

tronic antiaircraft gunnery task and the delivery of augmented visual

feedback during training. Individuals in the control condition tracked

each target plane using a group of dots as a cursor. Feedback was the

visual error between the dots and the moving target plane. Individuals

in the augmented feedback condition performed the same tracking task as

those in the control condition, but they received extra visual cues

(reddening of the target plane) when their responses were on target.

Individuals in the augmented feedback condition performed better

during training than individuals in the control condition, but they did

not learn more about the task than the controls. When subsequently required to perform in the absence of the supplementary visual cues, individuals in the experimental group performed no better than those in the

control group.

Experience with some variables, such as organizational strategies

(52,89), produces relatively permanent changes in performance. If the

effects of this experience persist after the variable has been removed,

the variable is said to be a learning variable (result B). For illustration, researchers us-ig a pursuit tracking task in which trainees could

9

-J 4
1.0

A

* //

m/

S1.0-

' *

ý1'

S Augmented

•/ Feedback

-No Augmented

Feedback

i•0 Rest

]{"Training Transfer

Figure 2. Hypothetical performance data for two groups trained with and

wi chout augmented feedback and then transferred to common

conditions after a rest interval.

10
see if they were on target found that performance was enhanced greatly

when feedback was augmented by a clicker that sounded when the trainees

were on target. The authors attributed this enhancement to learning

because the effect persisted after the clicker was removed (102).

Some variables, such as knowledge of results (76), appear to affect

both performance and learning. For these variables, th.. dissimilarity

between groups is reduced by a transfer test (result C). Some research

indicates that augmented feedback may work in this way, at least in certain situations (69).

By definition, performance variables do not have a direct effect on

learning or memory. An important reservation must be made, however. Any

variable, such as augmented feedback, that can enhance an individual's

motivation to perform a particular task also may induce him to practice

harder or more frequently; few doubt the importance of practice as a

variable for learning and memory (6). Thus, variables that raise (or lower) a person's motivation to perform a particular task also may act indirectly to determine what is learned and what is retained.

In summary, a variety of training procedures has been used to augment

feedback. Some, but not all, produce lasting benefits. Some have no effect on performance. Some conceivably could produce performance deficits

when withdrawn (25). It has been indicated that the transfer paradigm

provides a basis for evaluating formally the impact of training variables

such as augmented feedback on motor learning and performance. Informally,

however, the following generalization appears to have some empirical justification as a guide for evaluating a training procedure:

a subject must have some cues to the results of his actions

if he is to perform accurately at all., and training procedures

will be effective insofar as they help him to observe and use

such cues as are inherent in the task for which he is being

trained. They will fail insofar as they provide him with extra

cues on which he comes to rely but which are not available when

he changes from training to the actual job (343).

Individual Ability Levels

Tn the acquisition of motor tasks, individuals having higher initial

ability levels generally require less time to attain a specified criterion than individuals having lower initial ability levels. This conclusion appears to generalize across a wide range of military (50,55,141) and

nonmilitary (35,36,101) training conditions and a number of different operational definitions of the term initial ability.

iii

4 I'
Thus, research using eight training taski ranging in complexity from

a simple reaction time task (monitoring) to a combat plotting task problem solving (50), research using a 92-step procedural task (55), and

research using 13 Basic Training Skills (141) all defined initial ability

in ter'is of the trainees' Armed Forces Qualification Test scores and indicated faster learning by trainees who had higher mental aptitudes. Other

studies, defining initial ability in terms of the learner'e early performance on a to-be-retained balancing task (35,36) or using expert judgments

of motor proficiency as an index of initial ability on five novel gross

motor tasks (101) obtained analogous results.

In contrast, the weight of the evidence indicates that the rate at

which motor proficiency is lost is not related to a performer's initial

ability level (35,55,101,141). This is illustrated in Figure 3, which

presents hypothetical forgetting functions for three groups of varying

initial ability. Note that the functions are parallel to one another,

suggesting a common rate of forgetting. Also note that individuals of

higher initial ability achieve higher levels of proficiency during origi- nal training and retain their skill at a higher level over the retention

period than individuals of lower initial ability (141). As a consequence,

such individuals should require refresher training less frequently than

persons of lower initial ability. Furthermore, refresher training can be

shorter for persons of higher initial ability because they retrain to

standards more quickly than persons of lower initial ability (55).

Procedural Variables

Level of Original Learning

A number of authors (48,51) have described the learner's level of

original learning as the single most important determiner of motor memory. One study, using a three-dimensional flight-control task (48),

found extremely high positive correlations ,.80 to .98) between the

learner ' initial proficiency lcvels and later retention. This evidence

is compelling because the strength of these correlations did not dissipate through time. The relationship between original learning level and

retention remained high and stable over retention periods ranging from

1 month to 2 years.

Given the importance of original learning as a deteiminant of retention, some consideration must be given to the variables thought to contribute most heavily to the motor learning process. These are knowledge

of results, for example, "right," "wrong," "too long," "too short"; and

response-produced feedback, for example, proprioception, vision, and

audition.

12 i'
NMI:

r -- Ii

High I•nitial Ability -- ,- -- Averaga Initial Ability

S.... Law initiut Ability

Baseline Retention

Figure 3. Hypothetical forgetting functions for three groups of

varying initial ability.

13
Knowledge of Results. Knowledge of results refers to externally

provided error information about the discrepancy between a learner's actual response and the intended response. Announcements such as "right," "1"wrong," "3 inches too far" are examples of knowledge of results. An

account of the role of knowledge of results in motor learning is beyond

the scope of this report; there are several literature reviews available

on the subject (4,25,97,116). Two points from that literature, however,

are especially pertinent:

1. The early acquisition of a skill depends heavily upon knowled.

of results. Performance generally improves with knowledge of

results and deteriorates, or shows no further improvement, when

knowledge is withdrawn (24,96). Only later in learning, once a

performance has become "internalized," may knowledge of results

be withdrawn (or its absolute frequency reduced) without seriously impairing performance (96,118).

2. In the relationship between the amount of information provided by knowledge of results (its precision) and an individual's rate

of learning and final level of performance, the consistent finding (133) has been that performance is facilitated by increases

-in the precision of knowledge of results, but only up to a point.

If knowledge of results becomes too precise, that is, if the

amount of information provided by knowledge of results is increased beyond that which can be processed by the learner within

the time allowed, a decrement in performance will result (110).

In general, individuals who receive more and better knowledge of

results require less training time and achieve a higher end-of-training

performance level than those who do not. This suggests that any addel

effort to provide more or better knowledge of results to trainees would

be worthwhile. It also suggests that special attempts must be made to

facilitate the delivery of knowledge of results in situations that tend

naturally to inhibit the presentation of its information.

For example, a major source of difficulty in training many team tasks

is in detecting and correcting the er:ors of individual team members. Although a variety of factors contributes to this problem, it appears to

stem primarily from the interactive effects of the team members' responding and the difficulties involved in simultaneously monitoring the behavior of several individuals (142). If techniques could be devised to

facilitate the presentation of more or better knowledge of results in

situations like these, a higher level of trainee performance is likely

to be realized.

Response-Produced Feedback. The theoretical status of responseproduced feedback during motor learning is still controversial (3,5,67,

68), but few doubt its practical importance for the acquisition of new

motor responses. Most theorists (4,67) contend that early in learning,

the learner uses knowledge of results in relation with the feedback

14

S~~14 •

- 4
information he receives, for example, proprioceptive, visual, or auditory

cues, to establish a memorial representation of how a correct performance

feels, looks, and sounds. This representation is assumed to be weak initially, so the learner must depend heavily upon knowledge of results for

information about the correctness of his performance (24,96).

Later in learning, however, after a stronger represent'.-...... -f the

correct performance has been stored in memory, the learner i -- aeet and

correct movement erro;:s by comparing the feedback qualitte .:s present

performance with those of the stored representation. He no longer needs

to depend upon knowledge of results for information about the correctness

of his performance (96). This information is inherent in the feedback

that he has received from past performances and that he receives from his

present performance, and the information enables him to "know" when a

performance is correct in the absence of knowledge of results.

The notion (4) that motor learning and performance depend upon the

quantity, for example, number of feedback channels and amount of practice,

and quality, that is, fidelity, of the response-produced feedback the individual receives has solid empirical support. The more response-produced

feedback that the learner receives, the more accurate and confident he

becomes in his responding (6,7,8.llq). Also, retention is facilitated by

increasing the amount of original practice or number of available feedback

channels, for example, vision versus no vision. Evidence for this has J

been obtained under a wide variety of task conditions (87,94,134) and

retention intervals (10,14,130).

Increased levels of original training facilitate retention, but is it

cost effective to train beyond one successful performance, or is such

overtraining excessive and wasteful?

Overtraining, or mastery traiiinej, is important, and it may be more

cost effective than proficiency training, that is, training to some minimally acceptable level. Mastery training is known to enhance retentin

(58,85,92). This is a predictable result, but it has important implications for Army training policy. Currently, the Army relies heavily upon

combinations of proficiency training and refresher training. The problem'

is that refresher training involves time, personnel, and equipment costs

that cannot be minimized without first minimizing the need for refresher

training. One way to do this is to extend original training. If future

research should show that retention following mastery training equals or

exceeds retention following an equal amount of proficiency training plus

refresher training, a mastery training policy would appear to be the one

to adopt.

The benefits of mastery training extend beyond improved retention.

Theory (4,31,45,65,66) and data (27) suggest that the skilled performer

is able to devote less of his total attentional capacity to an ongoing

task than the novice. Mastery training thus frees the performer either

to attend to other tasks or to concentrate upon different aspects of his

main task.

15
Furthermore, there is evidence suggesting that mastery training may

reduce the inhibitory effects of anxiety-arousing or stressful environments upon performance (79). Stated another way, the stressful environment that may distract the less-skilled individual and disrupt his

performance may not seriously impair the highly skilled individual's

performance. If this hypothesis is supported by future research, it has

clear implications for Army training. In particular, the common belief

may be incorrect that troops must be trained under simulated combat or

other generally stressful conditions to react appropriately when placed

in an actual combat situation. Mastery training alone may protect a

soldier's performance from the interfering effects of an anxiety-arousing

or hostile environment.

Physical practice is important in the acquisition and performance of

motor tasks. However, there is evidence that the performance of some motor tasks can be enhanced as much or more by "mental practice" (104,105). One interpretation for this effect is that mental practice produces activity in the muscles involved in the performance of a task and that this

activity transfers positively to performance. Although this interpretation has empirical support (105), another more reasonable interpretation

is available. There is evidence that mental practice facilitates the cognitive, problem-solving aspects of motor learning. For example, predominantly motor tasks, such as tracking (128), show little benefit from

mental practice, whereas tasks that require the learner to depend heavily

upon intellectual, problem-solving skills, such as procedural tasks (105),

generally reveal substantial benefits due to mental practice.

Also, some physical practice on a task enhances the effectiveness of

mental practice. As physical practice continues, however, mental practice becomes increasingly less effective (122). This observation is consistent with the view that mental practice subserves verbal-cognitive

processing during motor learning. It is during the initial stage of motor

learning that verbal-cognitive activity is assumed to be prevalent (4,45,

Although clear evidence on mental practice is difficult to obtain

(105), closer scrutiny of the phenomenon is warranted. If, for exa.tmple,

mental practice alternated with physical practice can enhance or maintain

performance on hazardous tasks, such as disarming explosives, or infrto'-

quently performed tasks, such as launching missiles, the potential Lnefits are great.

Refresher Training

Time to retrain individuals to original performance levels is generally rapid, that is, consistently less than 50% of the original training

time (14,59,87). However, length of retraining time is much longer for

(a) longer retention intervals (14,95), (b) more difficult tasks (73), and

(c) for procedural tasks rather than continuous tasks (14,59,87). In

161
addition, highly trained individuals tend to require more training time

to regain their old levels of proficiency than less-trained individuals

(14,87). This latter result requires some clarification. Why should

forgetting increase with training? Although this effect may seem counterintuitive, it concerns forgetting in an absolute sense. Because highly

trained individuals have more to forget, they have more to relearn.

Several investigations using military personnel have demonstrated

that persons with practice during the retention interval perform better

than those with no practice (72,123,124,125). For example, an experiment

examining the effects of various practice strategies upon the long-term

retention of simulated manned spacecraft operations (124) showed that performance on the procedural aspects of the task deteriorated to an unacceptable level within 1 to 4 months of no practice.

At the end of 1 month of no practice, trainees required five times

longer to complete the procedural sequence than they did at the end of

training. Additional performance decrements were not evident after 2 and

3 months of no practice. However, after 4 months of no practice, trainees

required 17 times more time to complete the procedural sequence than they

did at the end of initial training. In sharp contrast to these data,

trainees afforded some form of practice during the retention interval

showed no signs of losing their end-of-training proficiency levels on the

procedural sequence over retention intervals measured up to 6 months.

Refresher training may provide opportunities for new learning. For

illustration, researchers using a team of aerospace test personnel showed

a substantial improvement over original training levels following

refresher training 13 weeks after original training (38).

Refresher training techniques may improve on-the-job safety and performance (38,51). In particular, development of practice modules for

safe practice of a dangerous or critical task immediately prior to actual

task execution may result in fewer accidents and a higher quality output

(123,124,125).

Warmup Activity. Closely related to the topic of refresher training

in the literature on the e.*ects of a preparation, or warmup period, on

retention test performance (M17). A warmup period can promote retention,

but it depends upon the particular task and warmup activity. Many intervening activities are ineffective as warmup activities, and some result in

poorer retention than a rest period (121). More research is needed on the

effectiveness of various warmup activities on particular tasks to clarify

this issue.

Some evidence (90) suggests that "neutral" tasks, involving activities unrelated to the task to be recalled, can be effective as warmup

activities. If this is the case, it has practical implications for the

Army. 1n particular, the introduction of a neutral warmup activity prior

17
to the performance of an infrequently performed, such as launching a

missile, or dangerous task, such as combat, may prove an effective means

of improving performance.

Transfer of Training

Transfer of training refers to the influence of past learning on new

learning. Learning one task may help in learning or performing another

task (positive transfer) or may interfere with the second task (negative

transfer). For example, the responses acquired while learning to drive

an automobile may alter tie responses one makes when learning to drive a

tank. Transfer depends upon the similarity of the stimuli and responses

involved in tasks A and B (61,62,63), the individual's level of learning

(1,42,61,75,78,145), and the difficulty of the tasks (17,61,77).

Positive transfer effects are observed typically when transferring

between motor tasks, but the strength of the effects are usually small

because of the differences between tasks and because of the effects of

forgetting (1). The observation of negative transfer depends primarily

upon how it is defined (23,61,62,63,75,80,82,117,145). If an overall

decrement in performance is required for negative transfer, then the

following conclusions are justified: Negative transfer is difficult to

produce and, when produced, it obtains in negligible amounts and rapidly

converts to positive transfer (23). If, however, negative transfer is

defined in terms of the occurrence of an occasional, intrusive wrong

response, then it may be a practical concern. Intrusion errors, although

isolated, can occur within an overall context of positive transfer (75),

and these errors may have serious c6nsequences for the human operator or

the equipment being operated. Thus, the pilot who is experienced with

one aircraft may have no problem, relative to the complete novice, handling the controls of a different aircraft up to the point when a fatal

error is caused by the pilot's previously established flight-control

responses (63). Although such errors can be avoided by training within

a controlled environment, such as uso of a simulator, training is

required.

Trace Decay and Interference

Trace decay and interference are theories of forgetting. Trace decay

theory states that information deteriorates from mem6ky solely as a function of time (2). One study indicates that information about discrete motor responses starts decaying as soon as it enters memory (129). However,

there is no evidence about the decay of continuous motor information and

the extent to which trace decay influences the retention of motor skill

over prolonged no-practice intervals.

18
Interference theory states that forgetting is caused by competition

from responses learned either before or after a response to be remembered.

When the acquisition of task A degrades the retention of task B, proactive

interference is said to have occurred. The acquisition of task A also may

enhance the retention of task B. This is known as proactive facilitation.

The inhibitory effect of task B on the retention of task A is known as

retroactive interference. The converse of retroactive interference is

known as retroactive facilitation.

Few investigations have been conducted of proactive (43) and retroactive (75,80,82) interference that used motor tasks and retention intervals longer than a few seconds. Based on the evidence obtained, it

appears that interference effects, like overall decrements due to negative

transfer, are difficult to produce and, when produced, persist typically

for little more than a handful of trials. Also, these effects appear to

be restricted to situations in which identical stimuli signal antagonistic

responses (117). Unless two tasks employ identical stimuli and require

antagonistic responses, facilitation effects can be anticipated generally.

Schedules of Practice

Continuous Tasks. Learning appears to be slower when practice sessions are longer and heavily massed than when they are shorter and occur

at more comfortable intervals (13). However, most motor learning theorists (61,117,121) are reluctant to conclude that spaced practice is more

conducive to learning and retention than massed practice. Rather, the

theorists contend that individuals practicing under massed conditions may

be more susceptible to the effects of boredom and fatigue than those practicing under spaced conditions. As a result, the relatively poor performance of individuals in the massed condition may not reflect the amounts

that they are actually learning. To support this contention, a substantial body of evidence (11,74,103) indicates that persons who are given

rest after practicing under massed conditions can demonstrate levels of

learning equivalent to those achieved by individuals practicing under

spaced conditions.

Although there is generally little or no dissimilarity in the retention of groups trained under massed and spaced practice schedules, an

important cautionary note is necessary. The acguisition of dangerous or

highly fatiguing tasks may be impaired under massed practice conditions

(117). That is, learning and performance may be hindered if the task is

too dangerous or too strenuous to be attempted repeatedly in the absence

of rest. In support of this hypothesis, the literature on vigilance

indicates that humans cannot maintain a high level of performance in tasks

that require continuous sustained attention (32). If rest opportunities

are not provided, individuals lose their motivation to perform or show

involuntary lapses of attention. If these lapses of attention accumulate,

they may hinder the early learning of persons in the massed practice condition relative to persons in the spaced practice condition (61).

19

!I

A
Discrete Tasks. In contrast to continuous tasks, the scheduling of

practice apparently affects neither the acquisition nor performance of

discrete tasks (37,117). No data are available concerning the effects of

different practice schedules on the acquisition and performance of procedural tasks. However, it is likely that the effects of distribution are

quite small and relatively unimportant when measured against the influence

of other learning variables. This hypothesis stems from both the observation that the distribution of practice typically has little or no effect

upon the acquisition of lists of verbal items having some degree of inter- - nal organization (138,139) and from the common belief that the motor

responses involved in most procedural tasks have a strong verbal component

(2,117). In the absence of further research, however, there is no way to

confirm or deny this hypothesis.

In summary, the manner in which practice occasions are arranged temporally generally does not have a strong effect upon individuals' final

level of original learning. The number of practice occasions offered is

an ýimportant variable. Therefore, in limited-duration training programs,

better retention should result using massed rather than spaced practice

schedules. The fact that massing allows more trials per unit time and

hence more opportunity for initial learning is the basis for this

interpretation (23,117).

Whcoie- Versus Part-Training Methods

The trainee may learn a task by practicing the entire task from the

beginning--whole practice--or by dividing the task into a number of discrete parts--part practice. In the part-practice situation, the ]earner

practices each part separately or in conjunction with other parts and

later integrates the parts to form the whole task. Obviously, there is

no way to define the meaning of the terms part or whole because specification depends upon the particular task (6J).

Four qeneral categories of variables seem to have an etfect upon the

effectiveness of part- versus whole-training raethods (91):

1. Task to be learned, for example, organization, difficulty;

2. Learner variables, for example, intelligence, age, experience,

preference;

3. Training situation, for example, amount of practice; and

4. Performance measures, for example, time or trial scores.

Task to Be Learned. The effectiveness of part- as opposed to wholetraining methods varies with the difficulty of a task's independent subtasks and the degree to which the subtasks are interrelated (53,61,117,

121):

20

A

~1
1. It generally is easier to learn simple to moderately difficult

tasks using whole-training methods rather than part--training

methods, whereas the opposite is true for more difficult tasks

(121).

2. Tasks requiring high coordination and timing of their serialmotor components are learned faster using whole-training methods.

In contrast, part-training methods tend to be more effective for

tasks that can be divided into meaningful independent subtasks

(30,93).

3. There appears to be an interaction between task difficulty and

task organization that influences the relative effectiveness of

part- and whole-training methods. Thus, training for tasks of

high organization becomes increasingly more effective with whole

practice as task difficulty increases. On the other hand, training for tasks of low organization is increasingly improved by

part practice as task difficulty increases (91,93).

Learner Variables. There is some evidence that more intelligent

individuals may learn and hence retain more using whole- rather than part- training methods. Evidence for this conclusion comes from a study of the

use of whole- and part-training methods to teach rifle marksmanship to

Army Basic Trainees (84). Although the whole-training method was found

to be superior in slow-fire routines for all trainees, the more difficult

task of sustained fire was facilitated when the whole method for only

trainees of above-average intelligence was used.

Individuals who are older (school-age subjects), who have more taskrelated experience, or who are performing a preferred task also tend to

learn faster and better when whole- rather than part-training methods are

used. These results have been interpreted in terms consistent with the

hypothesis that less difficult tasks are more amenable to whole- rather

than to part-training methods (91). This is a reasonable interpretation.

Presumably, a task is simpler for older, more intelligent, or more experienced persons. To the extent that a person's preference to perform a particular task may be related to task difficulty, it may be viewed as another condition under which task difficulty influences training-method

effectiveness.

Training Situation. As training continues, learning is increasingly

benefited by whole practice (91). Apparently, this is another instance

in which task difficulty is the variable underlying the effect. Practice

facilitates the ease of a performance, causing later learning to be more

amenable to whole- than to part-training methods.

Performance Measures. Different results are sometimes obtained when

different performance measures are used. In particular, time scores occasionally favor part-training methods whereas trial measures sometimes

favor the whole method. However, this effect appears to be artifactual

(91).

21

j
Part-Whole Learning and Long-Term Retention. A search of the wholeversus part-training method literature for information about the impact

of this training variable upon long-term motor memory was almost in vain.

One set of experiments was found on part-whole learning and long-term mo-I

tor memory (112,113). The author failed to show any differences, however,

between conditions during original learning and retention.

Although retention should benefit from the training method that

yields the higher original training level, both part- and whole-training

methods may produce substantially equivalent training outcomes (112,113).

Under these conditions, it may be more cost effective to use the part

method. The part method typically employs, or can employ, simulators (9) 3

that are usually lower in operating costs, more adaptable to trai1.ing

requirements, and less hazardous to the operator (140) than the operational equipment.

Additional Test Trials

Performance tests have been perceived traditionally as tests of

learning or memory. It is becoming increasingly clear, however, that test

trials themselves contribute to the learning process. Evidence concerning J

the effects of additional test trials, without knowledge of results, comes

primarily from studies of verbal memory; at least two conclusions appear

justified on the basis of it.

1. Memory is facilitated greatly by the addition of a test trial

given prior to final testing. For example, investigators studying the

long-term retention of verbal paired-associates found that the addition

of an immediate test, after 10 paired presentations of the stimulus and

response members of an item, reduced error frequency by nearly 50% as compared to 10 paired presentations without the retention test. in addition,

long-term retention, as measured by the individuals' response latencies as

well as their error frequencies, showed further improvements when five

test trials were introduced prior to the final retention test (12). Converging support for this conclusion comes from a host of experiments, many

of which have been reviewed elsewhere (15,108). In general, final test

performance is faster (44), more accurate (26,106,107), and more stable

(34), and relearning is quicker (108) when additional test trials, without

knowledge of results, are provided.

Evidence is lacking concerning the effects of additional test trials,

without knowledge of results, upon the retention of motor skill. Indeed,

this survey uncovered only one experiment on the topic. It involved the

acquisition and retention of a simple linear movement (41). Contrary to

expectations derived from the verbal learning literature, the introduction

of additional test trials during the retention interval did not aid retention. In fact, individuals in the experimental groups became increasingly

less accurate, that is, more variable, over successive test trials.

22

if
...... .. 

It may be that additional test trials introduced during the retention

interval do not enhance motor retention, but this seems very unlikely. As

has been indicated, additional test trials have clear, beneficial effects

upon the retention of verbal materials. There is no apparent reason to

expect that these effects differ across response classes. It would seem

more likely that the experimental design employed by these authors was

incapable of identifying the effects of additional test trials upon motor

retention. More research on this issue clearly is indicated.

2. Additional test trials are equally if not more beneficial to

learning and retention than study opportunities. A recent experiment

using a verbal memory task illustrates the effectiveness of additional

test trials as a variable for long-term retention (60). Researchers

tested groups of individuals for the retention of a list of words after a

48-hour retention interval. One group was exposed to the list four times

before the final retention test, that is, study-study-study-study-test.

A second group received a single presentation of the list and three test

trials prior to the final retention test, that is, study-test-test-testtest. Even though the former group was permitted four times more study

time on the list than the latter, the final retention of the latter group

was far superior to that of the former group.

A number of interpretations have been offered to account for the

facilitating effect of additional test trials on the retention of verbal

material (70). Perhaps the most plausible of these is that additional

test trials enhance the recovery of information from memory either by

facilitating its organization (28,40,111) or by enabling the learner to

develop a plan, or strategy, to retrieve the appropriate information at

the time of testing (57). It is also likely that test trials help the

learner to determine where learning is incomplete. Thus, on a given

training trial, the learner may recognize material he missed on the previous test trial and concentrate on that rather than devote further

attention to previously learned material (70,132).

The observation that additional test trials may be more beneficial

to learning than additional study time has important practical implications for training. In particular, it may be possible to reduce overall

training time, produce a more effective trainee, or both, simply by affording the trainee more test-taking opportunities. Tests of the gener- 2

ality of this hypothesis are necessary to determine whether additional

test trials facilitate the retention of a wide variety of tasks. The

Army Research Institute has begun research on this issue.

SUMMARY

This review is based upon a wide variety of data. Although militaryrelated findings were incorporated wherever possible, some of the experiments cited used tasks having little direct or obvious relationship with

skills currently maintained within the Army. In addition, conflicting

23
data and data pertinent to a more detailed understanding of the behavioral

consequences of an extended no-practice period generally were skimmed over

to lend coherence to this report. In so doing, an oversimplified picture

of long-term motor memory and the variables that may affect it has been

sketched. These constraints notwithstanding, a number of tentative conclusions have empirical support:

1. Discrete motor responses, particularly those involved in procedural tasks, are more likely to be forgotten over a nopractice period than are continuous motor r- sponses.

2. Retention of skill is a decreasing function of time, and the

shape of the function depends upon a host of variables, including the length of the no-practice period, the type of task, and

the availability of practice or the presence of interfering

activities before or during the retention interval.

3. Apparently, learners can impose organization upon psychologically unstructured tasks via the learning process. As a result,

task structure is not an important variable for the long-term

retention of well-learned responses, although it is an important

variable for the retention of less well-learned responses.

4. Functional similarity is a necessary and sufficient condition

for learning procedural tasks.

5. Display-control relationships can influence the ease of motor

learning and transfer and, to some degree, the quality of performance after a retention interval.

6. Visual cues designed to supplement the information provided by

a task display are informative early in learning and may facilitate the learning process. Later in learning, however, these

cues become relatively ,uninformative and unimportant as determiners of retention.

7. Augmented feedback can enhance performance by enhancing motiva- tion, learning, or both.

8. Individual ability levels are important as determiners of retention insofar as they influence a person's rate of learning and

final level of performance. Individuals of higher initial ability tend to achieve higher levels of proficiency and retain skill

at a higher level than individuals of lower initial ability.

9. The single most important determinant of motor retention is

level of original learning. Information obtained from knowledge

of results and response-produced feedback is thought to contribute most heavily to a trainee's rate of learning and final ievel

24
fV

of performance. Information provided by knowledge of results

increases with its availability and precision. Information

provided by response-produced feedback increases with its

quantity, for example, number of feedback channels and amount

of practice, and quality, that is, fidelity.

10. Refresher training can serve as an effective source of new

learning as well as a means for reestablishing forgotten

responses. Refresher training also may provide a relatively

simple means of improving on-the-job safety and performance.

11. Learning and retention are benefited by test-taking

opportunities.

12. Occasional, intrusive wrong responses induced by past learning

may have serious consequences for the human operator or the equipment he is operating.

CONCLUSIONS

Returning to the main issue: What procedures can the Army reasonably use to insure that its personnel remain job proficient over prolonged periods of no practice?

More basic and applied research is clearly indicated. Suggested

during the course of this review were a rumber of issues and avenues for

research aimed at increasing training effectiveness. Because long-term

retention appears to depend so heavily upon a traineets original learning

level, this would seem, at l.east initially, to be the most direct and

effective means of attacking the issue of skill maintenance in the Army.

Stepping up research efforts is not all that needs doing to foster

a more proficient Army trainee. Research has value but only insofar as

it permits inferences to be drawn about tLj effects of particular varables upon the retention of particular performances. Research does not

enable one to determine when a given individual or team lacks job proficiency. This fact is of fundamental importance if the Army is to have

a cost-effective refresher training program.

More emphasis must be placed upon the use of local individual proficiency examinations, for example, some more frequently administered

variant of the Skill Qualification Test. This would seem to be the simplest and most economical program to adopt. Those who fail to demonstrate proficiency can receive refresher training tailored to their specific needs. Those who retain their proficiency can be freed for other

duties.

25
Individual performance evaluations can provide other benefits to the

individual trainee as well as to those in supervisory positions. For example, the Job Performance Evaluation program currently being developed

by American Telephone and Telegraph Company (56) uses a uniformly applied

set of performance standards to judge objectively the quantity and quality

of work of individual employees. The employee is informed exactly what he

is being held accountable for and is told specifically how his performance

compares with management's expectations. As a result, the employee knows

deficiencies in performance and can modify the direction and level of his

efforts.

In addition, supervisors receive precise information about the productivity of individual subordinates by which they can (a) modify and

thereby improve training programs; (b) increase the validity of procedures

used to select and to promote employees; and (c) improve their own job

performance by learning more about the progress of their subordinates as

well as the progress of their work group as a whole.

The assessment of American Telephone and Telegraph's evaluation

program is only beginning: The success of the program to date is based

primarily upon anecdotal reports of improved employee productivity and

morale. Nevertheless, their program, or one like it, appears to be particularly suited to many Army requirements in this area and definitely

warrants the Army's consideration.

26 J
REFERENCES

1. Adams, J. A. Psychomotor response acquisition and transfer as a

function of control-indicator relationships. Journal of Experimental

Psychology, 1954, 48, 10-18.

2. Adams, J. A. Human memory. New York: McGraw-Hill, Inc., 1967.

3. Adams, J. A. Response feedback and learning. Psychological

Bulletin, 1968, 70, 486-504.

4. Adams, J. A. A closed-loop theory of motor learning. Journal of

Motor Behavior, 1971, 3, 111-149.

5. Adams, J. A. Issues for a closed-loop theory of motor learning.

In G. E. Stelmach (Ed.), Motor control: Issues and trends. New

York: Academic Press, 1976.

6. Adams, J. A., & Goetz, E. T. Feedback and practice as variables

in error detection and correction. Journal of Motor Behavior,

1973, 5, 217-224.

7. Adams, J. A., Goetz, E. T., & Marshall, P. H. Response feedback

and motor learning. Journal of Experimental Psychology, 1972, 92,

391-397.

8. Adams, J. A., Gopher, D., & Lintern, G. Effects of visual and

proprioceptive feedback on motor learning. Journal of Motor

Behavior, 1977, 9, 11-22.

9. Adams, J. A., & Hufford, L. E. Contributions of a part-task

trainer to the learning and relearning of a time-shared flight

maneuver. Human Factors, 1962, 4, 159-170.

10. Adams, J. A., Marshall, P. H., & Goetz, E. T. Response feedback

and short-term motor retention. Journal of Experimental Psychology,

1972, 92, 92-95.

11. Adams, J. A., & Reynolds, B. Effect of shift in distribution of

practice conditions following interpolated rest. Journal of

Experimental Psychology, 1954, 47, 32-36.

12. Allen, G. A., Mahler, W. A.,,& Estes, W. K. Effects of recall

tests on long-term retention of paired associates. Journal of

Verbal Learning and Verbal Behavior, 1969, 8, 463-470.

27

{I -
13. Ammons, R. B. Effect of distribution of practice on rotary

pursuit "hits". Journal of Experimental Psychology, 1951, 41,

17-22.

14. Ammons, R. B., Farr, R. G., Bloch, E., Neumann, E., Dey, M.,

Marion, R., & Ammons, C. H. Long-term retention of perceptualmotor skills. Journal of Experimental Psychology, 1958, 55,

318-328.

15. Anderson, R. C., & Biddle, W. B. On asking people about what they 1

are reading. In Bower, G. (Ed.), Psychology of learning and

motivation (Vol. 9). New York: Academic Press, 1975.

16. Bahrick, H. P., Noble, M. E., & Fitts, P. M. Extra-task performance |

as a measure of learning a primary task. Journal of Experimental

Psychology, 1954, 48, 298-302.

17. Baker, K. E., Wylie, R. C. & Gagne, R. M. Transfer of training to

a motor skill as a function of variation in the rate of response.

Journal of Experimental Psychology, 1950, 40, 721-732.

18. Battig, W. F., Nagel, E. H., VoEs, J. F., & Brogden, W. J.

Transfer and retention of bidimensional compensatory tracking

after extended practice. American Journal of Psychology, 1957,

70, 75-80.

19. Bell, H. M. Retention of pursuit rotor skill after one year.

Journal of Experimental Psychology, 1950, 40, 648-649.

20. Bernstein, B. R., & Gonzalez, B. K. Leaining, retention and

transfer: Vol. I of II (NAVTRADEVCEN Tech. Rep. 69-C-0253-1).

Orlando, FL: United States Naval Training Center, February

1971.

21. Bilodeau, E. A. Retention under free and stimulated conditions.

In E. A. Bilodeau (Ed.), Principles of skill acquisition. New

York: Academic Press, 1969.

22. Bilodeau, E. A. Supplementary feedback and instructions. In E.

A. Bijodeau (Ed.), Principles of skill acquisition. New York:

Academic Press, 1969.

23. Bilodeau, E. A., & Bilodeau, I. McD. Motor-skills learning.

Annual Review of Psychology, 1961, 12, 243-280.

24. Bilodeau, E. A., Bilodeau, I. McD., & Schumsky, D. A. Some effects

of introducing and withdrawing knowledge of results early and

late in practice. Journal of Experimental Psychology, 1959, 58, 142-144.

28
25. Bilodeau, I. McD. Information feedback. ILL E. A. Bilodeau (Ed.),

Principles of skill acquisition. New York: Acaderic Press, 1969.

26. Boker, J. R. Immediate and delayed retention effects of

interspersing questions in written instructional passages.

Journal of Educational Psychology, 1974, 66, 96-98.

27. Boucher, J. I-P. Higher processes in motor learning. Journal of

Motor Behavior, 1974, 6, 131-137.

28. Bregman, A. S., & Weiner, J. R. Effects of test trials in pairedassociate and free recall learning. Journal of Verbal Learning

and Verbal Behavior, 1970, 9, 689-699.

29. Briggs, G. E. Transfer of training. In E. A. Bilodeau (Ed.),

Principles of skill acquisition. New York: Academic Press, 1969.

30. Briggs, G. E., & Waters, L. K. Training and transfer as a function Al

of component interaction. Journal of Experimental Psychology,

1958, 56, 492-500.

31. Broadbent, D. E. Perception and communication. New York: -gamon,

1958.

32. Broadbent, D. E. Decision and stress. New York: Academic Press,

1971.

33. Buckout, R., Naylor, J. C., & Briggs, G. E. Effects of modified

task feedback during training on performance of a simulated

attitude contrnl task after thirty days (AMRL-TR-63-125). ,

Dayton, OH: gright-Patterson Air Force Base, December 1963.

34. Butler, D. C., & Peterson, D. E. Learning during "extinction"

with paired associates. Journal of Verbal Learning and Verbal

Behavior, 1965, 4, 103-106.

35. Carron, A. V. Effect of ability upon retention of a balance skill

after two years. Perceptual and Motor Skills, 1971, 33, 527-529.

36. Carron, A. V., & Marteniuk, R. C. Retention of a balance skill as

a function of initial ability level, Research Quarterly, 1970, 41,

478-483.

37. Catalano, J. F. The effect of rest following massed practice of

continuous and discrete motor tasks. Journal of Motor Behavior,

1978, 10, 63-67.

38. Cotterman, T. E., & Wood, M. E. Retention of simulated lunar

landing mission skills: A test of pilot reliability (AMRL-TR66-222). Dayton, OH: Wright-Patterson Air Force Base, April 1967.

29

iA
39. Department of the Army, Field Manual 100-5, Operations. Washington,

D.C.: July 1976.

40. Donaldson, W. Output effects in multitrial free recall. Journal

of Verbal Learning and Verbal Behavior, 1971, 10, 577-585.

41. Duffy, T. M., Montague, W. E., Laabs, G. L., & Hillix, W. A. The

effects of overt rehearsal on motor short-term memory. Journal

of Motor Behavior, 1975, 7, 59-63.

42. Duncan, C. P. Transfer in motor learning as a function of degree of

first-task learning and inter-task similarity. Journal of Experimental

Psychology, 1953, 45, 1-11.

43. Duncan, C. P., & Underwood, B. J. Retention and transfer in motor

learning after 24 hours and after 14 months. Journal of Experimental

Psychology, 1953, 46, 445-452.

44. Eimas, P. D., & Zeaman, D. Response speed changes ini an Estes'

paired-associate "miniature" experiment. Journal of Verbal

Learning and Verbal Behavior, 1963, 1, 384-388.

45. Fitts, P. M., & Posner, M. I. Human performance. California:

Brooks/Cole Publishing Co., 1967.

46. Fitts, P. M., & Seeger, C. M. SR compatibility: Spatial characteristics of stimulus and response codes. jurnal of Experimental Psychology, 1953, 46, 199-210.

47. Fleishman, E. A. A relationship between incentive motivation and

ability level in psychomotor performance. Journal of Experimental

Psychology, 1958, 56, 78-81.

48. Fleishman, E. A., & Parker, S. F. Factors in the retention and

relearning of perceptual-motor skill. Journal of Experimental

Psychology, 1962, 64, 215-276.

49. Fleishman, E. A., & Rich, S. Role of kinesthetic and epatialvisual abilities in perceptual-motor learning. Journal of Experimental Psychology, 1963, 66, 6-12.

50. Fox, W. L., Taylor, J. E., & Caylor, J. S. Aptitude level and

the acquisition of skills and knowledges in a variety of military

training tasks. (HumRRO Tech. Rep. 69-6). Alexandria, VA: Human

Resources Research Organization, May 1969.

51. Gardlin, G. R., & Sitterley, T. E. Degradation of learned skills--

A review and annotated bibliography (DISO-15080-1). Seattle, WA:

Boeing Company, June 1972.

30
52. Gentile, A. M., & Nacson, J. Organizational processes in motor

control. In J. Keogh & R. S. Hutton (Eds.), Exercise and sport

sciences reviews (Vol. 4). Santa Barbara, CA: Journal Publishing

Affiliates, 1977.

53. Goldstein, I. L. Training: Program development and evaluation.

Monterey, CA: Brooks/Cole, 1974.

54. Grimsley, D. L. Acquisition, retention, and retraining: Effects

of high and low fidelity in training devices (HumRRO Tech. Rep.

69-1). Alexandria, VA: Human Resources Research Organization,

February 1969.

55. Grimsley, D. L. Acquisition, retention, and retraining: Training

category IV personnel with low fidelity devices (HumRRO Tech. Rep.

69-12). Alexandria, VA: Human Resources Research Organization,

June 1969.

56. Gustafson, H. W. Job performance evaluation as a tool to evaluate

training. Improving Human Performance Quarterly, 1977, 5, 133-152.

57. Halff, H. M. The role of opportunities fo recall in learning to

retrieve. American Journal of Psychology, 1977, 90, 383-406.

58. Hammerton, M. Retention of learning in a difficult tracking task.

Journal of Experimental Psychology, 1963, 66, 108-110.

59. Hill, D. S. Minor studies in learning and relearning. Journal of

Educational Psychology, 1914, 5, 375-386.

60. Hogan, R. M., & Kintsch, W. Differential effects of study and

test trials on long-term recognition and recall. Journal of Verbal

Learning and Verbal Behavior, 1971, 10, 562-567.

61. Holding, D. H. Principles of training. Oxford: Pergamon Press,

1965.

62. Holding, D. H. An approximate transfer surface. Journal of Motor

Behavior, 1976, 8, 1-9.

63. Holding, D. H. Transfer of training. In B. B. Wolman (Ed.),

International encyclopedia of psychiatry, psychology, psychoanalysis,

and neurology. New York: AESCULAPIUS, 1977.

64. Jahnke, J. C., & Duncan, C. P. Reminiscence and forgetting in

motor learning after extended rest intervals. Journal of Experimental Psychology, 1956, 52, 273-282.

31B
65. James, W. Principles of psychology. Vol. 1. New York: Holt,

1890.

66. James, W. Principles of psychology. Vol. II. New York: Holt,

1890.

67. Keele, S. W. Movement control in skilled motor performance.

Psychological Bulletin, 1968, 70, 387-403.

68. Keele, S. W. Attention and human performance. Pacific Palisades,

CA: Goodyear Publishing Co., Inc., 1973.

69. Kinkade, R. G. A. A differential influence of augmented feedback

on learning and on perfonrance (WADC Air Force Systems Command

Tech. Rep. AMRL-TDR-63-12). Dayton, OH: U.S. Air Force, Wright

Air Development Center, 1963.

70. Lachman, R., & Laughery, K. E. Is a test trial a training trial

in free recall learning? Journal of Experimental Psychology, 1968,

76, 40-50.

71. Leavitt, H. J., & Schlosberg, H. The retention of verbal and motor

skills. Journal of Experimental Psychology, 1944, 34, 404-417.

72. Leonard, R. L. Jr., Wheaton, G. R., & Cohen, F. D. Transfer of

training and skill retention (TR-76-A3). Alexandria, VA: U.S.

Army Research Institute for the Behavioral and Social Sciences,

October 1976.

73. Lersten, K. C. Retention of skill on the Rho apparatus after one

year. Research Quarterly, 1969, 40, 418-419.

74. Lewis, D., & Lowe, W. F. Retention of skill on the SAM complex

coordinator. Proceedings of the Iowa Academy of Science, 1956,

63, 591-599.

75. Lewis, D., McAllister, D. E., & Adams, J. A. Facilitation and

interference in performance on the modified Mashburn apparatus: I. The effects of varying the amount of original learning.

Journal of Experimental Psychology, 1951, 41, 247-260.

76. Locke, E. A., Cartledge, N., & Koeppel, J. Motivational effects of

knowledge of results. Psychological Bulletin, 1968, 70, 474-485.

77. Lordahl, D. S. & Archer, E. J. Transfer effects on a rotary pursuit

task as a function of final task difficulty. Journal of Experimental

Psychology, 1958, 56, 421-426.

32

32 1i
78. Mandler, G. Transfer of training as a function of degree of response

overlearning. Journal of Experimental Psychology, 1954, 47, 411-

417.

79. Martens, R. Arousal and motor performance. In J. Wilmore (Ed.),

Exercise and Sport Sciences Review. New York: Academic Press,

1974.

80. McAllister, D. E. Retroactive facilitaticn and interference as

a function of level of learning. American Journal of Psychology, 1952, 65, 218-232.

81. McAllister, D. E. The effects of various kinds of relevant verbal

pre-training on subsequent motor performance. Journal of Experimental Psychology, 1953, 46, 329-336.

82. McAllister, D. E., & Lewis, D. Facilitation and interference in

performance on the modified Mashburn apparatus: II. The effects

of varying the amoutnts of interpolated learning. Journal of

Experimental Psychology, 1951, 41, 356-363.

83. McDonald, R. D. Retention of military skills acquired in basic

combat training (HumRRO Tech. Rep. 67-13). Alexandria, VA:

Human Resovrces Research Organization, December 1967.

84. McGuigan, F. J., & MacCaslin, E. F. Whole and part methods in

learning a perceptual motor skill. American Journal of Psychology,

1955, 68, 658-661.

85. Melnick, M. J. Effects of overlearning on the retention of a

gross motor skill. Research Quarterly, 1971, 42, 60-69.

86. Melton, A. W. Retention of tracking skills (DA-49-007-MD-1020).

Ann Arbor, MI: University of Michigan, September 1964.

87. Mengelkoch, R. F., Adams, J. A., & Gainer, C. A. The forgetting

of instrument flying skills. Human Factors, 1971, 13, 397-405.

88. Meyers, J. Retention of balance coordination learning as influenced by extended lay-offs. Research Quarterly, 1967, 38, 72-78.

89. Montague, W. E. Elaborative strategies in verbal learning and

memory. In G. H. Bower (Ed.), The psychology of learning and

motivation (Vol. 6). New York: Academic Press, 19i2.

90. Nacson, J., & Schmidt, R. A. The activity-set hypothesis for

warm-up decrement. Journal oý Motor Behavior, 1971, 3, 1-15.

91. Naylor, J. C. Parameters affecting the relative efficiency of

part and whole practice methods: A review of the literature

(NAVTRADEVCEN Tech. Rep. 950-1). Orlando, FL: U.S. Naval Training

Devices Center, February 1962.

33

.1;

-•,
92. Naylor, J. C., & Briggs, G. E. Long term retention of learned

skills: A review of the literature (ASD Tech. Rep. 61-390).

Canton, OH: Aerospace Medical Laboratory, Wright-Patterson Air

Force Base, August 1961.

93. Naylor, J. C., & Briggs, G. E. Effects of task complexity and

task organization on the relative efficiency of part and whole

training methods. Journal of Experimental Psychology, 1963,

65, 217-224.

94. Naylor, J. C., Briggs, G. E., & Reed, W. G. Task coherence,

training time, and retention interval effects on skill retention.

Journal of Applied Psychology, 1968, 52, 386-393.

95. Neumann, E., & Ammons, R. B. Acquisition and long-term retention

of a simple serial perceptual-motor task. Journal of Experimental

Psychology, 1957, 53, 159-161.

96. Newell, K. M. Knowledge of results and motor learning. Journal

of Motor Behavior, 1974, 6, 235-244.

97. Newell, K. M. Knowledge of results and motor learning. In J.

Keogh and R. S. Hutton (Eds.), Exercise and sport sciences reviews

(Vol. 4). Santa Barbara, CA: Journal Publishing Affiliates,

1977.

98. Noble, M., Trumbo, D., Ulrich, L., & Cross, K. Task predictability

and the development of tracking skill under extended practice.

Journal of Experimental Psychology, 1966, 72, 85-94.

99. Prophet, W. W. Long-term retention of flying skills: A review

of the literature (HumRRO Tech. Rep. 76-35). Alexandria, VA:

Human Resources Research Organization, October 1976.

100. Prophet, W. W. Long-term retention of flying skills: An annotared bibliography (HumRRO Tech. Rep. 76-36). Alexandria, VA:

Human Resources Research Organization, October 1976.

101. Purdy, B. J., & Lockhart, A. Retention and relearning of gross

motor skills after long periods of no practice. Research Quarterly,

1962, 33, 265-272.

102. Reynolds, B., & Adams, J. A. Motor performance as a function of

click reinforcement. Journal of Experimental Psychology, 1953,

45, 315-320.

103. Reynolds, B., & Bilodeau, I. McD. Acquisition and retention of

three psychomotor tests as a function of distributlon of practice

during acquisition. Journal of Experimental Psychology, 1952,

44, 19-26.

34
104. Richardson, A. Mental practice: A review and discussion, Part I.

Research Quarterly, 1967, 38, 95-107.

105. Richardson, A. Mental practice: A review and discussion, Part

II. Research Quarterly, 1967, 38, 263-273.

106. Richardson, J. The relationship of stimulus similarity and number

of responses. Journal of Experimental Psychology, 1958, 56,

478-484.

107. Richardson, J. Association among stimuli and the learning of

verbal concept lists. Journal of Experimental Psychology, 1960,

60, 290-298.

108. Richardson, J., & Gropper, M. S. Learning during recall trials.

Psychological Reports, 1964, 15, 551-560.

109. Roehrig, H. C. Psychomotor task with perfect recall after fifty

weeks of no practice. Perceptual and Motor Skills, 1964, 19,

547-550.

110. Rogers, C. A. Feedback precision and postfeedback interval duration. Journal of Experimental Psychology, 1974, 102, 604-608.

111. Rosner, S. R. The effects of presentation and recall trials on

organization in multitrial free recall. Journal of Verbal

Learning and Verbal Behavior, 1970, 9, 69-74.

112. Rubin-Rabson, G. Studies in the psychology of memorizing piano

music: I. A comparison of the unilateral and the coordinated

approach. Journal of Educational Psychology, 1939, 30, 321-345.

113. Rubin-Rabson, G. Studies in the psychology of memorizing piano

music: III. A comparison of the whole and the part method.

Journal of Educational Psychology, 1940, 31, 270-284.

114. Russel, R. W., Valentine, J. A., & Harris, F. J. Maintenance

of •unner proficiency in basic skills in a combat air force

Randolph Field, TX: 8th Air Force and Research Division, Central

School for Flexible Gunnery, January 1945.

115. Ryan, E. 0. Retention of stabilometer and pursuit rotor skills.

Research Quarterly, 1962, 33, 593-598.

116. Schendel, J. D., & Newell, K. M. On processing the information

from knowledge of results. Journal of Motor Behavior, 1976, 8,

283-287.

. 7 . Schmidt, R. A. Motor skills. New York: Harper, 1975,

35
118. Schmidt, R. A., & White, J. L. Evidence for an error detection

mechanism in motor skills: A test of Adams' closed-loop theory.

Journal of Motor Behavior, 1972, 4, 143-153.

119. Schmidt, R. A., & Wrisberg, C. A. Further tests of the Adams'

closed-loop theory: Response-prod,,ced feedback and the error

detection mechanism. Journal of Motor Behavior, 1971, 3,

318-325.

120. Shinar, D., & Acton, M. B. Control-display relationships on the

four-burner range: Population stereotypes versus standards.

Human Factors, 1978, 20, 13-17.

121. Singer, R. N. Motor learning and human performance. New York:

Macmillan, 1975.

122. Singer, R. N., & Witker, J. Mental rehearsal and point of intro-,

duction within the context of overt practice. Perceptual and

Motor Skills, 1970, 31, 169-170.

123. Sitterley, T. E. Degradation of learned skills: Static pr.--,,.ice

effectiveness for visual approach and landing skill retentiou

(D180-17876-1). Seattle, WA: Boeing Aerospace Company, May 1974.

124. Sitterley, T. E., & Berge, W. A. Degradation of learned skills:

Effectiveness of practice methods on simulated space flight

skill retention (D180-15081-1). Seattle, WA: Boeing Aerospace

Company, July, 1972. 4

125. Sitterley, T. E., Zaineff, L. P., & Berge, W. A. Degradation

of learned skills: Effectiveness of practice methods on visual

approach and landing skill retention (D180-15082-1). Seattle,

WA: Boeing Aerospace Company, October 1972.

126. Smith, N. C., Jr. Long-term retention of a pursuit motor skill.

Perceptual and Motor Skills, 1971, 32, 773-774.

127. Smith, J. F., & Matheny, W. G. Continuation versus recurrent

pilot training (AFHRL Tech. Rep. 76-4). Canton, OH: WrightPatterson Air Force Base, May 1976.

128. Smyth, M. M. The role of mental practice in skill acquisition.

Journal of Motor Behavior, 1975, 7, 199-206.

129. Stelmach, G. E. Retention of motor skills. In J. Whilmore (Ed.),

Exercise and Sport Sciences Review. New York: Academic Press,

1974.

36
130. Stelmach, G. E., & Kelso, J. A. S. Memory trace strength and

response biasing in short-term motor memory. Memory & Cognition

1975, 3, 58-62.

131. Swink, J. D., Trumbo, D., & Noble, M. On the length-difficulty

relation in skill performance. Journal of Experimental Psychology,

1967, 74, 356-362.

132. Thompson, C. P., Wenger, S. K., & Bartling, C. A. How recall

facilitates subsequent recall: A reappraisal. Journal of

Experimental Psychology: Human Learning and Memory, 1978, 4,

210-221.

133. Trowbridge, M. H., & Cason, H. An experimental study of Thorndike's theory of learning. Journal of General Psychology, 1932,

7, 245-258.

134. Trumbo, D., Noble, M., Cross, K., & Ulrich, L. Task predictability in the organization, acquisition, and retention of tracking skill. Journal of Experimental Psychology, 1965, 70,

252-263.

135. Trumbo, D., Noble M., & Swink, J. Secondary task interference

in the performance of tracking tasks. Journal of Experimental

Psychology, 1967, 73, 232-240.

136. Trumbo, D., Ulrich, L., & Noble, M. Verbal coding and display

coding in the acquisition and retention of tracking skill.

Journal of Applied Psychology, 1965, 49,'368-375.

137. Tulving, E., & Donaldson, W. Organization of memory. New York:

Academic Press, 1972.

138. Underwood, B. J. Ten years of massed practice on distributed

practice. Psychological Review, 1961, 68, 229-247.

139. Underwood, B. J., Keppel, G., & Schulz, R. W. Studies of distributed practice: XXII. Some conditions which enhance retention.

Journal of Experimental Psychology, 1962, 64, 355-363.

140. Valverde, H. H. A review of flight simulator transfer of training studies. Human Factors, 1973, 15, 510-523.

141. Vineberg, R. A study of the retention of skills and knowledge

acquired in basic training (HumRRO Tech. Rep. 75-10). Alexandria,

VA: Human Resources Research Organization, June 1975.

37

A
t60

142. Wagner, H., Hibbits, N., Rosenblatt, R. D., & Schultz, R. Team

training and evaluation strategies: State-of-the-art (HumRRO

Tech Rep. 77-1). Alexandria, VA: Human Resources Research

Organization, February 1977.

143. Welford, A. T. Fundamentals of skill. London: Methuen & Co.,

Ltd., 1968.

144. Wheaton, G. R., Fingerman, P. W., Rose, A. M., & Leonard, R. L.,

Jr. Evaluation of the effectiveness of training devices:

Elaboration and application of the predictive model (Research

Memorandum 76-16). Alexandria, VA: U.S. Army Research Institute

for the Behavioral and Social Sciences, July 1976.

145. Wheaton, G. R., Rose, A. M., Fingerman, P. W., & Korotkin, A.

L., & Holding, D. H. Evaluation of the effectiveness of training

devices: Literature review and preliminary model (Research

Memorandum 76-6). Alexandria, VA: U.S. Army Research Institute

for the Behavioral and Social Sciences, April 1976. I I

Al

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1 HOLCA (DAFDOMFA) 1 USA Infantry Hum Rsch Unit. Ft Banning, ATTN: Chief

1 K ..OA (DARD.ARS-P) I USA Infantry Bd, Ft Banning, ATTN: STECC-TE-T

1 HODA (DAPC.PAS-A) 1 USASMA, Ft Bliss, ATT~N: ATSS-LRC

IHODA (DUSA-OR) 1 USA Air Daf Sch, Ft Bliss, ATTN: ATSA--CTD -ME

IHODA IDAMO.ROR) I USA Air Daf Sch, Ft Bliss, ATTN: Tech Lib

IHODA IOASG) 1 USA Air Def Sd, Ft Bliss, ATTN: FILES

1 HODA (DAlO-PI) 1 USA Air Def Sd, Ft Bliss, ATTN: STEBD-PO

1 Chief, Consult Div (DA.OTSG). Adelphi, MD I USA Cmd & General Stf College, Ft Leavenworth, ATTN: Lib

1 Mil Asst. Hum Rles, ODDR8IE. QAD (E&LS) 1 USA Cmd &i General Stf College, Ft Leavenworth, ATTN: ATSW-SE-L

1 HO USARAL, APO Seattle, ATTN: ARAGP.R I USA Cmd & General StO College, Ft Leavenworth, ATT'N: Ed Advisor

I HO First Army, ATTN- AFKA.OI*TI 1 USA Combined Arms Cmbt 0ev Act. Ft Leavenworth, ATTN: DepCdr

2 HO Fifth Asmy, Ft Sam Houston I USA Combined Arms Cmbt 0ev Act, Ft Leavenworth, ATTN: CCS

I Dir, Army Stf Studies Ofc, ATTN: OAVCSA (DSP) 1 USA Combined Arms Cmbt Dee Act, Ft Leavenworth, ATTN: ATCASA

1 Dic Chief of Stf, Studies Ofc 1 USA Combined Aims Cmbt 0ev Act, Ft Leavenworth, ATTN4: ATCACO-E

1 DCSPER, ATTN: CPS/OCP 1 USA Combined Arms Cmbt Dev Act. Ft Leavenworth, ATTN: ATCACC-CI

1 The Army Lib, Pentagon, ATTN: RSB Chief 1 USAECOM, Night Vision Lab, Ft Belvoir, ATTlN: AMSEL-N V-SD

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I Ofc, Asst Sect of the Arm~y (R&D) 1 USAMERDC, Ft Salvoir, ATTN: STSFB-DO

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1 USAIMA, Ft Bragg, ATTN: ATSU.CTD.OM 1 USA Intelligence Ctr & Sets. Ft Huachuca, ATTN: ATS-CTD--MS

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1 US WAC Ctr & Sets, Ft McClellan, ATTN: Lib 1 USA Intelligence Ctr & Sch. Ft Huachuca, ATT'N: ATSI-TEX-GS

1 US WAC Ctr & Sets, Ft McClellan, ATTN: Tnig Dir 1 USA Intelligence Ctr & Sets, Ft Huachuca, ATTrJ: ATSI-CTS-OR

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I USATSCH, Ft Eustis, ATTN: Edue Advisor 1 USA Intelligence Ctr & Sets, Ft Huachuca, ATTN: Library

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1 USA Concept Anal Agcy, Bethesda, ATTN: MOCA.WGC I Hq MASSTER, USATRADOC, LNO

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1 FAA.NAFEC, Atlantic City, ATTN: Library I HOUSMC, Commandant, ATTN: Code MTMT 51

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1 USA Air Def Sch, Ft Bliss, ATTN: ATSA TEM

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I USA Aviation Sch. Res Tnig Mgt, Ft Rucker. ATTN: ATST-T-RTM

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4BiihDfStaff, British Embassy, Washington 40

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