Device for measuring fatigue effects

A field portable performance assessment device having an adaptive information processing test programmed therein. The device is used to measure psychological data of personnel working in a real-world environment such as in an aircraft. A microcomputer drives a unique numeric-symbolic display that the test subject must respond to by activating a particular switch. The device is about the size of a hand-held calculator and operates on internal power for extended periods.

BACKGROUND OF THE INVENTION 
This invention relates to the field of psychological data collection, and 
more particularly, to a psychological testing device having an adaptive 
information processing test program therein. 
Many of the past psychological testing devices have been so cumbersome that 
their use was confined to the laboratory. Although this may not be 
considered a problem in some circumstances, the artificial environment 
would defeat truly reliable performance assessment where the real-world 
environment cannot be factually replicated in the laboratory. These major 
obstacles make virtually impossible performance data collection because 
personnel were not actually engaged in their real-world tasks. This is 
especially so if personnel performance occurred in aircraft such as 
fighters where space is clearly at a premium, and the working environment 
is a substantial factor. 
SUMMARY OF THE INVENTION 
There currently exists, therefore, a need for a field portable performance 
assessment device that is about the size of a hand-held calculator and 
that can be programmed with a psychological test. The present invention 
overcomes the problems encountered in the past and described hereinabove. 
The invention is a small, battery powered device about the size of a 
hand-held calculator. The device has a box-like case with a cover. The 
cover has a window therein to view the operating condition of the device. 
The case has an input/output terminal port, a power terminal port, an 
audible alarm port, a first multi-position display, a second display, a 
plurality of input switches, a plurality of mode selection switches, a 
plurality of control switches, and a microprocessor programmed to control 
the information presented in the displays. Responses via the input 
switches are stored in a data memory which is dumped to a processing 
computer after testing. The device has an internal power source and can 
operate for extended periods such as two weeks. 
One object of the invention is to provide a field portable performance 
assessment device having programmed therein an adaptive information 
processing test for measuring psychological data in a real-world 
environment. 
Another object of this invention is to provide a programmable 
self-contained device capable of storing data for an extended period of 
time such as two weeks. 
Another object of this invention is to provide capability to capture and 
store a subject's report of feelings of fatique and workload. 
Another object of this invention is to provide a field portable performance 
assessment device that interfaces with a general purpose computer for data 
processing. 
Another object of this invention is to provide a field portable performance 
assessment device that facilitates ease of operation and acceptance by the 
subjects under study. 
Another object of this invention is to provide a field portable performance 
assessment device that insures data integrity. 
These and many other objects and advantages of the present invention will 
be readily apparent to one skilled in the art of psychological testing 
from a perusal of the claims and of the following detailed description of 
a preferred embodiment of the invention when considered in conjunction 
with the drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Reference is made to FIGS. 1, 2 and 3 of the drawing which disclose in 
pictorial fashion a field portable performance assessment device 10 of 
this invention. 
FIG. 1 illustrates field portable performance assessment device 10 having a 
cover 12 and a case 14. Both cover 12 and case 14 are constructed of 
durable, stiff plastic material. Cover 12 may be hinged to case 14 along a 
top joint 16, or a left side joint 18 (FIG. 2), or may be completely 
removable. Hinging is preferred since cover 12 may become misplaced and/or 
interfere with the operation of an aircraft. The method of hinging is 
conventional. Cover 12 has a window 20 therein so that the test subject 
can observe a date/time shown in a first display 22, shown in FIG. 3, to 
confirm the functioning of device 10 without opening cover 12. 
Instructions and subjective report scales may be mounted on cover 12. 
Cover 12 is useful also if there is an interlock between cover 12 and case 
14 to prevent entry of data until required wherein opening of cover 12 
would deactivate device 10. Cover 12 is constructed of a front panel 24, 
shaped essentially as a rectangle and four sides 26, 28, 30 (shown in FIG. 
2), and 32 (not shown), shaped essentially as rectangles. Cover 12 and 
case 14 in the closed state waterproof the interior of device 10. The 
overall dimensions of device 10 are approximately four inches by seven 
inches by one and one half inches. Further, any ports in device 10 should 
be waterproofed to prevent water or moisture from invading the interior 
also. An input/output terminal port 34 is located on a top side 36 of case 
14. The terminal located therein, not shown, can be connected to a general 
purpose computer 38, shown in FIG. 4. A conventional multi-pin male plug 
with cord attached can be inserted into port 34 for transferring 
information between device 10 and computer 38. In addition, an audible 
alarm port 40 is located on a right side 42 of case 14. An alarm therein 
sounds when the test subject is required to respond to the test programmed 
therein. 
Referring to FIG. 2, the back of device 10 is illustrated. On a back side 
44, a lockable lid 46, with a locking device 48, covers a mode select 
section 50. Operation of mode select section 50 is discussed at a later 
point hereinafter. 
Referring to FIG. 3, case 14 is shown separated from cover 12. Case 14 has 
six rectangular sides, a front side 52, back side 44, top side 36, a left 
side 54, right side 42, and a bottom side 58 (not shown). A battery power 
terminal port 60 is included on bottom side 58, shown in ghost outline. A 
conventional battery charger, not shown, is connected into the battery 
power terminal to recharge batteries 62 in FIG. 4. Placement of battery 
power terminal port 60 on bottom side 58 is preferred since a battery 
charging receptacle, not shown, but conventional, could hold device 10 so 
that a trickle charger charges batteries 62; thus device 10 could be 
immediately used without waiting. Batteries 62 are of sufficient capacity 
to operate device 10 for a period of about two weeks. An indication of low 
battery power could be repeated audible alarms. 
The other components forming part of case 14 and including various retainer 
brackets and the like included therein in order to hold the various 
components, as for example, batteries 62, could all be formed of a 
suitable plastic material, as for example polyethylene, polystyrene, 
polybutadiene or the like. Again, these various plastics which form cover 
12 and case 14 and some of the components could all be formed in 
conventional plastic molding operations, as for example, thermo-forming, 
injection molding, or the like. Again, other material as for example, 
metals, including aluminum or steel may also be employed for this purpose. 
Front side 52 of case 14 has mounted therein first display 22, a second 
display 64, a plurality of input switches 68, and a plurality of control 
switches 66. First display 22 is a conventional multi-position display, 
preferably a liquid crystal display (LCD) to reduce power drain, having 
sufficient positions to display the date and time. Display 22 is viewed 
through window 20 of cover 12. 
Second display 64 has a plurality of display positions, preferably LCD to 
reduce power drain, such as displays 70, 72, 74, 76, and 78 forming an 
"X". Display 74 is located at the center of the "X" and the other displays 
70, 72, 76 and 78 are located on the arms of the "X". A display 80 is 
located to the right side of the "X". Displays 70, 72, 74, 76 and 78 have 
only one position for display of a symbol ranging from one to five. 
Display 80 also has only one position for display but a variety of symbols 
such as an ".about.", "#", "*", "&gt;", or "[" can be displayed. Each symbol 
is assigned a particular number according to the adaptive information 
processing test such as 1.ident.#, 2.ident.*, 3.ident.&gt;, 4.ident..about., 
and 5.ident.[. The numbers one to five can appear in any display 70, 72, 
74, 76 and 78, no number being repeated. A symbol as noted above is 
displayed in display 80. The test subject prior to the test learns the 
relations between the symbols and the numbers. The test subject responds 
by pressing a particular push-button input switch 68 as noted below. 
Input switches 68 are conventional, except that the 1, 3, 5, 7 and 9 
positions are highlighted to form a similar "X" as noted in second display 
64. Depending on the symbol displayed in display 80 and its corresponding 
numeric reference, the test subject would press the position in switches 
68 that correspond with the position of the numeric reference of the 
symbol shown in second display 64. Input switches 68 can be used to enter 
other information such as date, time, subjective fatigue and workload 
response, etc. 
Control switches 66 are press-button activated switches such as an ENTER 82 
and an ERASE 84. Other control keys can be provided as needed. 
Referring to FIG. 2, mode select section 50 has a mode switch 51 for 
selecting various modes of operation of device 10. T position is the 
training mode in which device 10 cycles continuously through a data 
collection period; DO is the data output mode used to transfer the data 
memory directly to computer 38; AM is the alarm mode normally used to 
select the desired data collection period schedule and to set the correct 
date and time; RM is the research mode used to collect data in the field; 
and TM is the test mode used as an internal self-check to assure proper 
functioning. 
Referring to FIG. 4, the electronic functional block diagram of an 
electronic processing means 91 of device 10 is illustrated. Microcomputer 
86 is powered by internal battery power 62 and communicates through 
input/output device 90 including first display 22, second display 64, 
input switches 68, control switches 66, alarm 40, mode select section 50, 
and input/output terminal port 34. Memory retention by data storage memory 
and program memory is required when device 10 is powered down. General 
purpose computer 38 is connected to input/out terminal port 34 so that 
data stored may be dumped into computer 38 for data processing. Further 
computer 38 can reprogram device 10 so that a variety of testing programs 
may be used. A preferred program for device 10 is the adaptive information 
processing test having the logic flow diagram of FIG. 5 to be discussed 
hereinafter. 
The means of connecting input/out device 90, computer 38, microcomputer 86 
and power 62 is conventional and is therefore not described in any further 
detail herein. The devices making up field-portable performance assessment 
device 10 are conventional such as microcomputer 86 which can be composed 
of several integrated circuit chips. The switches of device 10 are 
conventional and provide only one input signal upon each actuation and 
must be released and pressed again before the switches can provide another 
input signal. The displays are conventional in form and can be 
light-emitting diodes, liquid crystal displays, etc. with the LCD 
preferred because of lower power consumption. 
To develop a task sensitive to fatigue stressors, the following factors 
have been taken into account in developing the adaptive information 
processing test used in device 10: 
(1) Monotonous tasks and those with high complexity or difficulty but 
relatively low interest are highly sensitive to sleep loss; 
(2) Self-paced tasks show little loss in accuracy but total response time 
increases with sleep loss; 
(3) As the time available for making a response increases, the task becomes 
less sensitive; 
(4) The longer a task lasts, the more sensitive it is to sleep loss; 
(5) Tasks measuring blocking or gaps tend to be most sensitive to sleep 
loss; 
(6) Tasks requiring continuous performance, not providing breaks or rest 
pauses, are more sensitive to sleep loss; 
(7) Tasks requiring minimal physical activity are more sensitive to sleep 
loss; 
(8) Sleep loss tends to increase reaction time (RT), but not consistently; 
(9) Knowledge of results (KR) increases resistance to sleep loss; 
(10) Newly acquired skills or tasks that have not been well practiced or 
have not reached a plateau in learning are suceptible to sleep loss. 
Tasks making severe short-term memory demands are also susceptible to sleep 
loss, but this factor is not to be incorporated into the test. 
In order to develop a task which is useable in field operations, the 
following further practical requirements have been considered in 
developing the adaptive information processing test of device 10: 
(1) The test should be easily and quickly learned to a stable baseline 
level; 
(2) The duration of the test should be as short as possible so as not to 
induce any significant, additional workload or fatigue on the operator and 
to keep interference with ongoing operations to a minimum; 
(3) The test should be easy to administer; 
(4) The test should be resistant to spoofing or guessing; 
(5) The test should be as resistant to changes in motivation as possible; 
(6) The test should be nonauditory in nature because of varying noise 
levels in operational settings and varying degrees of hearing loss found 
in operators; 
(7) The test apparatus should be capable of being made highly portable with 
its own independent power supply; 
(8) The measurement technique must be generally acceptable to the 
population under investigation. 
In order to satisfy the operational requirements as well as possible with a 
test that would be sensitive to sleep deprivation, the inventor developed 
a complex, five-choice visual RT task and incorporated it into a 
computer-based adaptive logic presentation system. It has been termed the 
Adaptive Information Processing Test. 
The distinctive feature of an adaptive logic system is that the subject's 
response is fed back to modify the difficulty level of the next stimulus 
presentation, based on how well the subject is performing. One of the 
earliest uses of this concept was the development of programmed 
instruction techniques in which the training material was presented in an 
order according to a predetermined criterion of student progress. 
In an adaptive tracking task, during the course of a continuous tracking 
period, the subject's integrated error score is used to adjust the 
difficulty level of the task to maintain the error score at a preset 
criterion. It has been found that this technique requires less time to 
train the subject to a baseline criterion than fixed tracking. There are 
several reasons for this. First, training time is more productive because 
little time is wasted giving the subject practice at a difficult level 
which is either already mastered or entirely above his present capability. 
Secondly, and just as important, the subjects maintain high motivational 
levels on this type of task. They are given an optimum challenge no matter 
how hard they try. They cannot succeed; yet they never experience severe 
failure. The adaptive tracking task has been extended to jet flight 
stimulator training. The turbulence input to a fixed-base Universal 
Digital Operational Flight Trainer Tool was modified continually as a 
function of how well the students were able to hold the simulated aircraft 
within a given criterion of reference altitude. It was found that when 
compared to a group of students conventionally trained, they improved more 
rapidly and made fewer errors. There was also some indication that, rather 
than having developed problems in controlling a secondary variable, such 
as airspeed, they had developed a control strategy which reduced other 
errors as well. 
A variation of adaptive technology has been applied to the secondary task 
approach to assess reserve capacity. In this case the difficulty of the 
secondary task is adjusted on the basis of primary task performance in an 
attempt to quantify and control the operator effort expended in 
maintaining various levels of performance. 
In the adaptive task developed, refer to FIG. 5, and used in field portable 
performance assessment device 10, the rate of stimulus presentation is a 
function of the latency of the prior response time and error rate. The 
computer increases the rate of presentation until the subject's 
information processing capacity is overloaded. This presentation rate is 
taken as the test subject's threshold of information processing capacity. 
There are two sources of overload in this task: first, the processing 
threshold at which the subject can no longer keep up with the presentation 
rate; and second, a block in which the subject cannot respond for a short 
period of time, regardless of the presentation rate. To the extent that 
the latter block is not indicative of the true information processing 
threshold, the subject is given a second chance to lower the threshold. 
But as the blocking becomes more frequent with fatigue, it will become the 
predominant source of overload. 
The task consists of the following steps: The subject must first learn an 
association between five symbols and a corresponding numeral from 1 to 5. 
Each trial consists of a display of one of the symbols and all give 
numbers in random pattern. The test subject must press a button 
corresponding to the location of the number which has been associated with 
the displayed symbol. This information processing task requires four 
subtasks: (a) recognition of the symbol; (b) recall of the number-symbol 
association from long-term memory; (c) search for the location of the 
correct number; and (d) the motor response to push the location of the 
correct button. It is felt that this task provided the required complexity 
level yet would not require a lengthy training period. Guessing is easily 
detected since the probability of responding correctly by guessing is only 
0.2. 
The adaptive logic of the task is as follows, referring to FIG. 5: the 
subject is initially presented displays in a self-paced mode to which he 
responds as fast as he can; the computer averages the reaction time (RT) 
for the first four correct responses and from this point on the rate of 
presentation of the panels is computer-paced; the computer presents each 
panel initially for the duration of the self-paced RT score; and the 
determination of the subject's initial response capability saves task 
presentation time since if the task was started at a fixed presentation 
interval, it would have to be slow enough to encompass the slowest initial 
response time expected from any subject at any level of fatigue. 
The task is designed to be simple enough that the subject will almost 
always respond correctly. Wrong answers are scored primarily to protect 
against those who might try to guess. If he makes two errors before he 
gets four correct, the presentation rate is reduced by 100 ms. If he gets 
four right before he gets two wrong, the presentation rate is increased by 
100 ms, up to the rate where he blocks. A block is defined as the 
presentation of two panels in a row to which the subject does not respond. 
The presentation rate at which this occurs is recorded. When a block is 
detected, two self-paced presentations are made to allow the subject to 
recover his concentration. However, there is no rest pause provided during 
this period. The speed of presentation is then reduced by 300 ms and the 
adaptive presentation logic is continued. The duration of the task is 
variable; it lasts only as long as it take for the subject to make two 
successive blocks within 200 ms of each other. 
Thus the task contains both paced and unpaced components. It is primarily 
computer-paced but it responds to the overload condition by slowing the 
presentation rate just as the subject would if he were in control. 
The average response time when blocking occurs has been found to be about 
600 ms. From pilot studies it has been found that the total task time 
required for a subject to block within the prescribed limits is normally 
about 60 seconds and the subject will normally produce from two to four 
blocks to reach criterion. Note that the definition of a block is relative 
in that it is based on the ongoing presentation rate. 
The use of a high-speed computer is critical to this type of adaptive 
technology since it permits a continuous task to be presented to the 
subject, scored, and modified, with delays which are imperceptible to the 
subject. The computer utilizes overload information to adapt the speed of 
presentation to the information processing capability of the subject. But 
the computer is capable of presenting and scoring the task faster than any 
subject can keep up with, and thus can always present the displays and 
score the responses at rates faster than the subject's processing 
threshold speed. 
Numbers 1 to 5 appear randomly in display section 64 on the left side of 
display 64. One of the five symbols appears on the right of display 64: #, 
*, .about., &gt;, or [. There are 120 possible number patterns that can be 
generated with 5 numerals. When paired with one of the five symbols, 600 
unique stimulus patterns are created. 
In an initial pilot study of this test, two sets of randomized displays 
containing subsets of four data files were constructed in the following 
manner: first, 300 of the unique displays were randomly assigned to the 
first set; the remainder were assigned to the second; next each group of 
300 was randomly assigned to 1 of 4 subsets, 75 to each subset; then 10 
from the total display set were randomly selected and assigned to each 
subset for a total of 85 displays per subset. The random selection process 
is arranged so that each symbol and each correct response location on the 
push-button panel occurred 17 times in each data file of 85 stimulus 
patterns. Additionally, the data file is inspected and when two identical 
symbols appeared in a row, the second is randomly assigned to a new 
location in the list. This is done in order to make it easier for a 
subject to recognize that a new trial is being presented. Both sets of 
files were stored in the computer. 
The subjects were required to memorize the following number-symbol 
associations: 1.ident.#, 2.ident.*, 3.ident.&gt;, 4.ident..about., and 
5.ident.[. The subject's task was to press input switches 68 which 
corresponded to the position of the numeral associated with the symbol 
displayed in display 80. See FIG. 3. The subject was instructed to 
continue responding to the task, as rapidly as possible, as long as 
displays were presented. 
In addition, the subjects were instructed to respond only when they knew 
the correct response. A subject learned that wrong answers slowed the 
presentation rate, and that the task would not end until he caused it to 
speed up to the point that he was unable to keep up with it when 
attempting to give correct answers. 
Another feature of this device is that every time the Adaptive Information 
Processing Test is completed, the subject can enter his subjective 
feelings of fatigue by pressing one of the input switches 68. Refer to 
FIG. 5. Input switches 68 labeled one to seven correspond to seven levels 
of a fatigue checklist, printed on the inside of cover 12. The subject's 
response will be stored along with his corresponding information 
processing test score. He would then enter his subjective feeling of his 
current workload estimate, also from a scale of one to seven using a 
workload checklist printed on the inside of cover 12. The device has a 
programmable audio alarm in alarm port 40 to alert the subject to each 
data collection period. There is a capability for a maximum of 16 data 
collection periods per day for 14 days for a total of 224 data collection 
periods which will be stored in the device. Data to be stored each period 
consists of an adaptive information processing score, a subjective fatigue 
score, a subjective estimate of workload, and a code to identify the date 
and time of the data collection period. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings and it is therefore understood 
that, within the scope of the disclosed inventive concept, the invention 
may be practiced otherwise than specifically described.