TASK-CONTROL OF 

AROUSAL AND THE 

EFFECTS OF REPEATED 

UNIDIRECTIONAL ANGULAR 

ACCELERATION ON HUMAN 

VESTIBULAR RESPONSES 

63-29 

FEDERAL AVIATION AGENCY 

AVIATION MEDICAL SERVICE 

AEROMEDICAL RESEARCH DIVISION 

CIVIL AEROMEDICAL RESEARCH INSTITUTE 

OKLAHOMA CITY, OKLAHOMA 
TASK-CONTROL OF AROUSAL AND THE 

EFFECTS OF REPEATED UNIDIRECTIONAL 

ANGULAR ACCELERATION ON HUMAN 

VESTIBULAR RESPONSES 

WILLIAM E. COLLINS, Ph.D. 

Chief, Sensory Integration Section 

Psychology Branch 

63-29 

FEDERAL AVIATION AGENCY 

CIVIL AEROMEDICAL RESEARCH INSTITUTE 

AERONAUTICAL CENTER 

OKLAHOMA CITY, OKLAHOMA 

NOVEMBER 1963 
TASK- CONTROL OF AROUSAL AND THE EFFECTS 

OF REPEATED UNIDIRECTIONAL ANGULAR 

ACCELERATION ON HUMAN VESTIBULAR RESPONSES1 

WILLIAM E. COLLINS, Ph.D. 

Wendt ( 1951) has indicated that habituation (a response decline) of human nystagmus 

may depend upon the conditions under which 

the response is repetitively elicited. He says 

". . . visual stimuli tend to inhibit the vestibular nystagmus, and with repetition these 

stimuli become increasingly dominant. Such 

habituation is probably not preventable." In the 

absence of visual stimulation, he has indicated 

that the loss of nystagmus " ... is preventable 

by keeping the subject attentive to the external 

surrounds and avoiding inward-directed revery 

states." 

Hence, in addition to specifying the importance of the conditions of elicitation, Wendt 

( 1951) has distinguished between two kinds 

of habituation. One of these is a loss of a state 

of attentiveness toward, or interest in the surrounds. The other, and the more usual way of 

regarding the phenomenon, refers to a real 

change in the properties of the system that 

should be independent of fortuitous subjective 

variations such as attitudinal or attentional 

factors. 

Wendt's concern with the importance of subjective states has been amply vindicated in 

recent studies which have shown that simple instructions regarding mental activity can markedly modify nystagmic behavior and that a 

high state of arousal, attention, or alertness, regardless of where it is focused, results in a 

vigorous nystagmic response (Collins, Crampton & Posner, 1961; Collins & Posner, 1963; 

Guedry & Lauver, 1961, Lidvall, 1962; Mahoney, Harlan, & Bickford, 1957). Further, it 

I Study conducted with the skillful technical assistance of 

Kenneth J. Gall and Kenneth E. Swain while the author was 

at the U. S. Army Medical Research Laboratory, Fort Knox. 

Kentucky. Additional assistance in data reduction rendered 

by Carolyn Roulston, Mary Jayne Capps, Joseph E. Duchon, 

and H. Gerald Hobelmann is gratefully acknowledged. 

has been demonstrated that all of the characteristics of "habituation" can appear as early as 

the first exposure of individuals to rotatory 

stimulation by simply instructing them to relax 

and daydream (Collins, 1962) . Such instructions literally abolish the response from some 

subjects and markedly reduce it from most. 

Apparently, with vision not permitted and in 

the absence of instructions or techniques designed to maintain attention, subjects soon become 

relaxed and lapse into reverie states. Concomitantly, nystagmic activity declines and may 

eventually cease. This type of response decline, 

then, is readily demonstrable and equally readily reinstatable ( cf. Collins & Guedry, 1962; 

Guedry, Collins & Sheffey, 1961). 

The present study was designed to examine 

the effects of repeated mild angular accelerations in total darkness on human nystagmus 

while subjects performed a number of attentiondemanding tasks. The latter were employed in 

an effort to obviate the influence of declining 

alertness and to "drive" the response on every 

trial. Further, "habituating" stimuli were 

limited to CW accelerations; decelerations were 

sub-threshold. Thus the question of whether nystagmus habituation could be directionally specific was examined. As a further point of interest, data pertaining to the subjective experience of rotation were collected to determine: 

(a) if subjective habituation could occur in the 

absence of visual cues; (b) if such habituation 

could be made directionally specific; and (c) if 

it could occur as a result of repeated stimulation while the subject's attention was directed 

elsewhere. 

Apparatus and Procedure 

Apparatus 

Rotatory. The turntable has been described 

by Guedry and Kalter ( 1956). It was located 

in a light-proof enclosure and was equipped 

-1-
an adjoining room. 

Task-stimulators. A Hewlitt-Packard 205A9 

Oscillator was used to provide stimuli for most 

of the tasks assigned to the subjects. The oscillator was a source of both auditory and vibratory stimuli. The former were presented to the 

subject by means of a pair of standard earphones. Vibration was applied to the subject's 

forefinger by a Good mans ( 4-ohm) Model V58 

vibrator. The plastic extension of the vibrator 

protruded slightly through the hole in the left 

arm-rest of the subject's chair. 

In all cases, the oscillator-frequency for the 

auditory stimulus was 700 cps; that for the 

vibratory stimulus was 250 cps. Stimulus intensity was maintained at a 30dB level above the 

subject's absolute threshold (obtained daily) 

during experimental sessions. A set of 3 interconnected Hunter Timers provided control over 

the duration of stimulus presentation. 

Recording. All data were recorded on an 

Offner Type-T Electroencephalograph. A 1.4 

sec RC time constant was used in amplification 

for nystagmus tracings. These tracings were obtained by means of a pair of electrodes taped 

by the outer canthi; an indifferent electrode was 

located on the mastoid process. Subjective responses were recorded (DC) by means of a telegraph key positioned on the right arm-rest of 

the chair. Depression of the key produced a pen 

deflection on the recorder; release of the key 

returned the pen to its original base-line. Similar deflections were produced by the timers, 

thereby indicating the duration of a given taskstimulus. Acceleration periods were recorded in 

a like manner. 

Tasks 

Subjects were given a period of instruction 

concerning the tasks and received actual practice in all but that requiring estimation of subjective velocity. In the latter case, they were 

given several demonstrations (with the experimenter performing the role of the subject) and 

asked to use only vestibular information in 

making their judgments. 

Reaction time. At frequent points throughout 

a trial, subjects were presented with a tone, or 

with a vibratory stimulus, of one-half sec duration. Subjects were instructed to respond to the 

the telegraph key. 

Temporal estimation of stimulus-filled intervals. Subjects were presented with a series of 

tones or vibrations during a trial. Each stimulus lasted for a period ranging between 0.5-6.5 

sec (in 1-sec intervals). At the conclusion of a 

stimulus, subjects were to reproduce its duration by depressing the telegraph key for the 

same period of time as that occupied by the tone 

or the vibration. 

Temporal estimation of stimulus-bounded 

intervals. Brief (one-half sec) tonal or vibratory stimuli were presented to indicate the onset and conclusion of an intervening period of 

no stimulation. The intervening periods ( unfilled intervals) ranged in duration from 0.5-

6.5 sec in 1-sec steps. Thus, e.g., a half-sec tone 

would be followed by 4.5 sec of silence, and 

then by another half-sec tone. The subject 

would then reproduce the duration of the silent 

(unfilled) interval by depressing the key for 

his estimate of the length of time between the 

two tones. A series of these stimuli were presented throughout a trial. 

Estimation of subjective velocity. Subjects 

were instructed in the technique of estimating 

angular displacement from their subjective experiences (Bekesy, 1955; Guedry & Lauver, 

1961). Specifically, they were required to signal, by depressing the telegraph key, the onset, 

cessation, and each experience of 90 ° rotation. 

A warning signal was presented 10 sec prior to 

the initiation of an acceleration to alert the subject to the impending stimulus. When the subject signalled cessation of experienced rotation, 

he was instructed to remain attentive for any 

further rotatory sensations, however weak, 

which he might experience (e.g., a secondary 

reaction - a sensation of turning in the opposite direction without an adequate stimulus 

-Guedry, Cramer, & Koella, 1956). Such 

experiences were to be reported at the conclusion of the trial. Ten sec prior to deceleration (1 min and 50 sec after termination of 

acceleration) a second signal was presented 

which notified the subject that he could close 

his eyes and relax until the conclusion of the 

trial. This task was used only in the preliminary and post-tests. 

-2-
TABLE 1 

Procedural Outline for the Pre- and Post-Test Trials. Decelerations Were Always Sub-Threshold (0.18 ° / Sec 2 ). MA Refers to 

Mental Arithmetic Tasks, and ESV to Estimates of Subjective 

Velocity. The Rest Period Between Trials 4 and 5 Was 15 Minutes 

Long. 

ACCELERATION 

TASKS 

1 2 

cw ccw 

MA MA 

3 

cw 

MA 

Mental arithmetic. Subjects were required to 

do arithmetic problems consisting of silent, 

continuous division (Collins, 1962). A problem 

was assigned just before a given trial and a signal to begin work was presented 10 sec prior 

to acceleration. A second signal, to stop work, 

was presented 10 sec prior to deceleration ( 1 

min and 50 sec after termination of acceleration). Subjects jotted down their final answer 

(in darkness) on a pad secured to the arm-rest 

of the chair. They then closed their eyes and 

relaxed until the conclusion of the trial. This 

task was employed during the preliminary and 

post-tests, and for trials 1, 2, 199, and 200 during the habituation series. 

Subjects 

The 10 subjects were all male volunteers, experimentally naive, physically healthy, and 

without any past history of ear difficulties, 

dizziness, or unusual reactions to linear or angular motion. They ranged in age from 19-26 

years with a mean of 22.8. They were cautioned to maintain normal sleeping hours, to abstain 

from alcohol, and to report the intake of any 

medicinal drugs during the course of the experiment. Subjects were well motivated and it is 

unlikely that any of these factors influenced 

the results. 

Procedure 

Subjects were seated upright on a chair 

mounted on the rotating platform. A biteboard 

positioned their heads so that the horizontal 

semicircular canals were approximately in the 

plane of rotation. Earphones were worn during 

all trials and series of angular accelerations 

4 

ccw 

MA 

TRIALS 

REST 5 6 7 8 

cw ccw cw ccw 

ESV ESV ESV ESV 

were administered in total darkness over 13 

daily sessions. Twelve sessions were on consecutive days; the thirteenth occurred exactly 4 

weeks after the twelfth. 

The first, twelfth, and thirteenth sessions were 

termed, respectively, preliminary (pre), post-1, 

and post-2 sessions. Each of these consisted of 

8 trials (a trial is defined as a complete acceleration cycle, i.e., acceleration to constant 

velocity to deceleration to stop). The acceleration direction for each of these trials was alternately clockwise ( CW) and counterclockwise 

( CCW). During the first 4 trials, subjects were 

assigned mental arithmetic problems; during 

the last 4, they made estimates of subjective 

velocity (see Table 1). 

Sessions 2 through 11 each consisted of 20 

trials (habituation sessions). For this total of 

200 accelerations, rotation was always in a CW 

direction. Tasks were assigned prior to each 

trial (see Table 2). In all of these trials, a signal was presented to the subject 10 sec prior 

to deceleration ( 1 min and 50 sec after termination of acceleration) to indicate that his 

task was completed and that he could close his 

eyes and relax until the conclusion of the trial. 

All trials comprised the following: ( 1) 30 

sec at a constant velocity of 1 rpm; (2) an acceleration of 4.15 ° / sec2 for 13 sec; (3) 120 

sec at a constant velocity of 10 rpm; ( 4) a deceleration of 0.18 ° / sec 2 for 333 sec to zero 

velocity. Rest periods of 3-5 min with the room 

illuminated separated the completion of one 

trial and the beginning of the next. Thus, acceleration stimuli were separated by a total of 

11-13 min. An additional 15-min rest period 

-3-
ORDER OF TASK-PRESENTATION FOR THE 200 HABITUA TION TRIALS. THE 1 0 SESSIONS, EACH COMPRISING 2 0 

TRIALS, WERE HELD ON CONSECUTIVE DAYS. SOUND 

WAS USED AS THE STIMULUS DURING ALL TRIALS IN 

THE ODD-NUMBERED SESSIONS: VIBRATION WAS USED 

DURING ALL TRIALS IN THE EVEN-NUMBERED SESSIONS. MA REFERS TO MENTAL ARITHMETIC, R T TO REACTION TIME, AND FI AND BI TO FILLED AND BOUNDED INTERVALS, RESPECTIVELY. 

SESSIONS 

TRIALS I II III IV v VI VII VIII IX X - 1 MA FI BI BI FI FI BI BI FI FI 

2 MA FI BI BI FI FI BI BI FI FI 

3 FI FI BI BI FI FI BI BI FI FI 

4 FI FI BI BI FI FI BI BI FI FI 

5 FI FI BI BI RT RT BI BI FI FI 

6 FI RT RT RT RT RT RT RT RT RT 

7 FI RT RT RT BI BI RT RT RT BI 

8 RT BI FI FI BI BI FI FI BI BI 

9 BI BI FI FI BI BI FI FI BI BI 

10 BI BI FI FI BI BI FI FI BI BI 

REST 15 MINUTE REST PERIOD 

11 BI BI FI FI FI FI FI FI BI BI 

12 BI BI FI FI FI FI FI FI BI BI 

13 BI BI FI FI FI FI FI FI BI FI 

14 BI RT RT RT FI FI RT RT RT FI 

15 FI FI BI BI RT RT BI BI FI FI 

16 FI FI BI BI RT RT BI BI FI RT 

17 RT FI BI BI BI BI BI BI FI FI 

18 FI RT RT RT BI BI RT RT RT FI 

19 FI FI BI BI BI BI BI BI FI MA 

20 FI FI BI lH BI BI BI BI FI MA 

- 4-
the turntable separated trials 10 and 11 (see 

Table 2). Immediately prior to each trial, calibrations of the horizontal displacement of. the 

subject's eyes were made and subjects were encouraged to be attentive and accurate in the 

performance of their tasks. 

Scoring 

All nystagmus records were analyzed into 3 

measures: duration of response, slow-phase 

displacement, and frequency of beats. For the 

latter two, records were scored in 5-sec intervals 

throughout the course of the reaction. Durations 

were calculated from the onset of acceleration 

to the concluding phase· of the last beat of 

primary nystagmus. Slow-phase eye deviation 

was scored by summing the slow-phase displacements of each nystagmic beat, from peak to 

base-line, per 5 sec interval. These values were 

converted to degrees of eye movement by means 

of the calibration factor. Frequency of nystagmus was determined simply by counting the 

number of beats within each interval. 

Of the 2,080 trials conducted, only 5 records 

were not scored. Two of these were from the 

habituation series and, due to technical difficulties, no records were obtained. The remaining 3 were one pre-test (Trial 1 for RW) and 

2 post-2 trials (Trials 1 and 2 for LM). In 

these cases, failure of a timing mechanism to 

perform properly resulted in interrupted stimulations. The obtained nystagmus was not scored 

for these incomplete accelerations. 

Results 

Effects of Stimulus Repetition 

Some examples of recorded nystagmus appear in Figure l. The post-test tracings clearly 

indicate a brisk nystagmus in spite of the preceding 200 acceleration exposures. However, 

the form of the response differs from that displayed in the pre-test. The intervening series 

of habituating trials induced an overall decline 

in the amplitude of nystagmus, and an increase 

in its frequency during the early seconds of the 

response. Figure 2 presents this relationship 

more clearly. For both the practiced and unpracticed directions of response, the first posttest shows a decline in slow-phase output relative to the pre-test performance. A further drop 

is evident in post-test-2, given one month later 

ences were evident in the frequency measures 

for both the practiced and unpracticed directions. Specifically, during the first 20-25 seconds of the response, the frequency of nystagmus increases from the pre- to the post-tests. 

However for the remainder of the response 

curve, the frequency shows a drop in post-test-1 

and, although still below its original level, some 

recovery in post-test-2. 

Figure 3 provides a direct comparison of 

the effects of the habituation series on post-test 

responses in the practiced and the unpracticed 

directions. There are negligible differences between the two directions in the pre-test, with 

the exception of the markedly longer duration 

for the CW direction. This difference is attributable to a single subject (RB) who yielded a 2-

minute response to his first acceleration. Slowphase output declined for both directions in 

post-test-1. However, it apparently declined 

differentially: relatively more for the unpracticed direction during the stimulus period, and 

relatively more for the practiced direction during the remainder of the response. The relation· 

ship between the slow-phase data for the two 

directions in post-test-2 resembles more closely 

lhe pre-test, although a further overall drop is 

evident. 

The frequency plots in Figure 3 are of particular interest. With no significant pre-test 

differences evident between the two directions, 

the post-tests demonstrate an increase in frequency of nystagmus during the stimulus 

period, and a depression of activity after that 

time. This increase is clearly greater for the 

practiced direction. One month later (post-test2), an overall frequency increase is evident for 

both directions, particularly during the stimulus period. 

Plots of average total output appear in Figure 4. It is clear that some drop in the total 

slow-phase activity and the average response 

duration occurs for both directions from the 

pre-test to post-test-1. An additional decline is 

evident in post-test-2 despite the lack of any 

subsequent intervening stimulations. For frequency measures, little change in total activity 

is evident for the practiced direction; the unpracticed direction tends to decline by about 

732- 432 0 - 64- 2 -5-
TRIALS 

1-CW 

2-CCW 

3-CW 

4-CCW 

1-CW 

2-CCW 

3-CW 

4-CCW 

1- cw 

PRE TEST 

POST-I TEST 

POST-2 TEST 

20-DEG 

I 

I 

I 

I 

I 

I 

I 

I 

2- ccw ~·---~~VV1/"""""""""'M.i~"""""~ ........... -"'V-""'V.....,....~-.........,..------..,_ 

I 

I 

3-CW 

4-CCW 

SUBJECT KS STIMULUS 4.1• I SEC2 FOR 13 SEC 

fiGURE l. Nystagmus recorded during pre- and post-test mental arithmetic tasks. Vertical bars 

through records demarcate the stimulus period. Eye calibrations are at the right of 

each tracing. Note the increased response frequency in post-1 trials following 200 CW 

stimulations. Post-2 trials show no evidence of recovery to the pre-test level although 

one month with no intervening trials had elapsed between post-1 and post-2 tests. 

-6-

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PRACTICED DIRECTION 

---...... PRE 

o-----<) POST - t 

....,____. POST - 2 

AVERAGE FOR 10 SUBJ£CTS 

50 60 70 80 90 100 110 120 

TIME IN SECONDS 

40 50 60 70 

14 UNPRACTICED DIRECTION 

12 

10 20 30 40 50 60 70 

FIGURE 2. Average nystagmus slow-phase and frequency curves for pre- and post-test data 

plotted in 5-sec intervals. An overall depression of slow-phase output is eviQ.ent for 

both the practiced and unpracticed directions. For frequency data, a depression 

affects only the tail of the curve; an increased frequency response occurs during the 

stimulus period and for a few seconds thereafter. 

PRE 

PRACTICED DIRECTION ......... 4 TRIALS 

UNPRACTICED DIRECTtON o--o 4 TRIALS 

AVERAGE: FOR 10 SUBJECTS 

24 POST-I 

20 

to 20l040506070 

" TIME IN SECONDS 

24 POST-2 

20 

10 20 lO 40 so eo 10 

14 

FIGURE 3. A time-course comparison of frequency and slow-phase nystagmus responses in 

practiced and unpracticed directions during the pre- and post-tests. The clearest 

differences appear in the post-test frequency responses during, and for a few seconds 

after, the stimulus period favoring the practiced direction. Compare with Figure 2. 

-7-
20 

tiffi~ 40 

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5~~ w::Ez 30 

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PRE 2 3 4 5 6 7 8 9 10 POST-I POST-2 

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PRE 2 3 4 5 6 7 8 9 10 POST-I POST-,2 

ll -- PRACTICED DIRECTION o--o UNPRACTICED DIRECTION 

AVERAGE FOR 10 SUBJECTS 

0 

• 0 

• 

PRE 2 3 4 5 6 7 8 9 10 POST-I POST-2 

FIGU RE 4. Average response-per-trial for each of the 13 experimental sessions. A gradual decline during the 10 habituation sessions is evident for both slow-phase and dura tion 

data; an increase occurs in frequency of nystagmus. Pre- to post-test declines in 

slow-phase and duration of nystagmus are somewhat greater for the practiced direction ; overall frequency of nystagmus shows little change. 

PRACTICED DIRECTION 

-- MENTAL ARITHMETIC 

o----o SUBJECTIVE VELOCITY ESTIMATION 

70 

AVERAGE RESPONSE FOR PRE, 

POST-I, AND POST-2 TESTS 

80 100 110 

TIME IN SECONDS 

120 

20 UNPRACTICED DIRECTION 

I~ 

10 

eo 

FIGU RE 5. A time-course comparison of pre- and post-test nystagmus output to mental arithmetic trials and to trials in which subjects estimated angular velocity. Since separate 

curves for pre-. post-1. and post-2 tests all showed the same relationship favoring 

output during the arithmetic trials, curves were averaged over the 3 sessions. 

-8-

70 eo 
TRIALS 

2 

50 

100 

150 

199 

200 

HABITUATION SERIES 

SUBJECT RB : STIMULUS 4.1°/ SEC 2 FOR 13 SEC 

FIGURE 6. Nystagmus tracings obtained during the habituation series. Trials 1, 2, 199, and 

200 comprised mental arithmetic tasks. The middle 3 tracings were obtained while 

the subject was engaged in making estimations of temporal intervals. Markings are 

the same as in Figure 1. 

-9-

20 -DEG 

I 

I 

-- I 

I 
series on the frequency response during, and for 

a few seconds after the angular acceleration 

(Figures 2 and 3). 

There was no large difference evident between the output of nystagmus obtained during 

the mental arithmetic (MA) tasks and during 

those in which estimates of subjective velocity 

were made (Figure 5). However, differences 

slightly favoring MA trials were consistent for 

each of the pre- and post-tests. 

The Habituation Series 

In addition to pre- and post-test data, Figure 

4 provides a session-by-session plot of the 

nystagmus data for the habituation series. The 

points represent the average response-per-trial 

for the 20 trials in each session. A fairly steady 

decline is evident from session to session in both 

z QU) 40 

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It should be noted that the differences in output 

levels between pre-test data and those of the 

habituation series are due primarily to the 

rather rapid decline within the first few habituation trials (Figure 6). 

Figure 7 provides an indication of the course 

of the various response outputs over trials. In 

this case, each point represents an average of 

the 10 sessions. Gradual declines are evident for 

all 3 measures from trials 1 through 10. Increased output occurs in all cases for trial 11 

(after a rest period) following which another 

gradual decline occurs. The greatest range of 

trial-to-trial differences occurs in the slowphase data and amounts to about 25 per cent; 

for frequency, it is less than 20 per cent; and 

for the duration, less than 15 per cent. 

ffio 

~ 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 

a: 

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70 

60 

50 

400 

300 

200 

2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 

{ 

10 SUBJECTS AND 

AVERAGES FOR IO SESSION$ 

2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 

TRIALS 

FIGURE 7. Analysis of nystagmus output during the 20 daily trials. Each point is an average 

for the 10 habituation sessions. Trial-to-trial declines are not marked and an increased out put occurs uniformly for trial 11 after. a 15 min rest period. 

-10-
60 SESSION 1 SESSION U 

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50 SESSION IX SESSION :Z: 

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30 ~ ~ 

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TRIALS 

fiG li HE 8. Trial-by-lrial plots of nystagmus durations for the habituation series. 

-11-
500 SESSION I SESSION II 

400 

300 

200 

5 10 15 20 5 10 15 20 

Ul 400 1- SESSION m SESSION l!r 

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200 

10 15 20 5 10 15 20 

TRIALS 

F IGURE 9. Trial·by·tri al plots of slow·phase nystagmus output for the ' habituation series. 

-12-
70 SESSION I 

60 

50 

40 

5 10 15 

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SESSION n 

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SESSION Jlr 

5 10 15 20 

SESSION Jlt 

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5 10 15 20 

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10 15 20 

SESSION X 

FICUHE 10. Trial·by·lrial plols of the nystagmus frequency data for 1he hahilualion serie>. 

-13-
tion, slow-phase, and frequency respectively. 

These graphs indicate that: 

(a) The most significant and striking losses 

in slow-phase output and in duration occur 

within the first few trials of the first session. 

The average response never returns to those 

early levels in any future trial. 

(b) Changes thereafter are much more 

gradual and there is no sharp, progressive trialto-trial decline within a session. 

(c) A different relationship obtains for the 

frequency data. 

Subjects were well motivated and carefully 

instructed prior to each trial. Consequently, 

only 19 of the 2,000 habituation series records 

showed the wandering eye movements characteristic of loss of attention. In each case, these 

changes occurred while subjects were estimatSUB.ECT LH 

new sound or vibratory stimulus while the subject was in the process of responding to a 

previous one (Figure 11). Such a procedure 

apparently marshalled the subject's attention 

processes to the assigned task. 

Wandering eye movements similar to those 

depicted in Figure 11 were also seen when deceleration recordings were obtained. Other examples of deceleration responses appear in 

Figure 12. The secondary nystagmic reactions 

evident in the tracings of the latter figure were 

not infrequent occurrences. Such responses were 

observed in 1,058 of the habituation records

beginning shortly after termination of the 

primary reaction and, quite often, still apparent when deceleration began. On some occasions, secondary responses seemed to be enhanced by the deceleration (see Figure 12), bu

this was not a consistent finding. 

~,_..__..."" I 20 OEG 

FIGURE 11. One of the 19 instances in which wandering eye-movement and unclear nystagmus 

·were obtained. The subject was engaged in estimating temporal intervals. The 

arrow indicates the point at which a new task stimulus was presented while he 

was still in the process of responding to a previous one. Nystagmus was immediately 

restored. Markings are the same as in Figure I. 

-14-
SUBJECT RB SESSION PRE- 1 

cv 

ACCEL ~ 

DECEL 

SUBJECT HS ::iESSION N -1 

ACCEL "-""~~..r----r---~~-

cv 

DECEL 

SUBJECT HW SESSION ll- 7 

ACCEL ~ ""-'" ""'~ ~~ \ \'\ \ t"\ \\\J\ \ \\"-1~ ~·"'-\r-~~_J 

·"--1 -r ··· \) V\, 

cv 

DECEL 

SUBJECT HW SESSION W- 7 

ACCEL ~~tr~"'~~~-A----~~----·'-!'' r- cv 

DECEL v' ~ 

FIGURE 12, Some examples of secondary nystagmus and of deceleration responses. The tracings 

are not continuous but are tnterrupted where the 3 dots appear. Other markings are 

the same as in Figure L RB shows no secondary reaction and no directionally specific activity during deceleration. Secondary nystagmus is present for both HS and HW. 

Such responses were frequently still in progress when the period of constant velocity 

( CV) ended, but in only some cases did they appear to be enhanced by the decelera· 

lion stimulus (as in the HW, Session Il-7 record) . 

Subjective Angular Velocity 

Subjective responses were scored by measuring the amount of subjective displacement, signalled by the key pressing technique, within 

each 5-sec interval. Since each signal represented 90 ° of experienced angular movement, the 

measurements were readily converted to degrees of displacement. 

Four trials each in the pre-test and the two 

post-tests provided subjective rotatory data for 

both CW and CCW accelerations. Plotted results appear in Figure 13 for 8 of the 10 subjects. For the pre-test, no essential difference 

between the two curves is apparent. However, 

post-test-1 indicates a clear decline for the CW 

direction and post-test-2 shows some recovery, 

albeit not complete, after one month with no 

intervening stimulation. From Figure 14 it is 

clear that the subjective impressions of angular 

velocity in the CCW direction were not at all 

affected by the 200 CW habituation trials. 

Data from two subjects are not included in 

Figures 13 and 14. Both gave abnormally long 

subjective responses during the pre-test and, to 

prevent possible distortion, their data were not 

included in the average curves. It is possible 

that they may have .responded to non-vestibular 

cues or, perhaps, that they fell into a rhythm 

of key pressing although their sensation had 

diminished. The latter effect has been noted in 

the training of subjects (F. E. Guedry, personal 

communication). 

-15-
60 

>-

!:: 50 u 0 

0 z ...J 0 

ILl u 

> ILl 40 1/) 

ILl a:: > ILl i= Q. 

u 30 ILl 1/) 

.., ILl IJ) ILl 

:::> a:: 1/) C) 

ILl 

ILl 0 

C) 

<l ~ a:: 

ILl 

~ 

POST-I 

~ 

! ·:L_~~~~~~~~~~~~ POST-2 

TIME IN SECONDS 

-l"ttACTICIO 

OMOT>OO 

-- UMNACTIC[CI 

Olltt:CTIOfil 

FIGURE 13. Subjective velocity estimated during pre· and post-tests. Each poi nt represents an 

average of 2 trials per subject. Arrows indicate moment of stimulus termination. 

Intensity of the subjective reaction is considerably diminished in post·1 for the prac· 

ti ced direction. Post·2 test shows some recovery. 

PRACTICED DIRECTION UNPRACTICED DIRECTION 

• • PRE 60 

C>----<> POST- I 

• • POST- 2 

AVERAGE FOR 8 SUBJECTS 50 

40 

30 

20 

10 

10 20 30 40 50 60 70 10 20 30 40 

TIME IN SECONDS 

FIGURE 14. A direct time-course comparison of pre· and post·test output for the practiced 

and for the unpracticed directions. The latter shows little or no change. The 

practiced direction shows a substantial decline in amplitude from the pre-test to 

post·l. Recovery is evident in the second post-test given 1 month later. Note that 

the duration of the subjective response is not reduced after the 200 accelerations 

interposed between the pre· and post-1 tests. 

-16-

50 60 
Human Nystagmus Habituation 

Rotation studies. Griffith ( 1920b) employed 

10 rotatory trials per day for approximately 4 

weeks and found an average response loss in 

16 subjects of 79 per cent for both frequency 

and duration of nystagmus. His data showed a 

major decrease in the first few trials and he 

noted that, when subjects had organic disturbances or had just undergone physical exertion, 

nystagmus improved temporarily. Griffith 

( 1924) reported his own response to be still 

below its original output level some 4 years 

later, with no intervening stimulation. However, 

in his study, as well as in those of Holsopple 

(1923; 1924) who also found nystagmus habituation, visual fixation was permitted. 

Dodge (1923) subjected himself to 114 rotation trials per day for 6 days. He recorded nystagmus with eyes closed and reported eventual 

abolishment of the response to his deceleration 

stimulus (which was initiated while the acceleration response was going on) and a 50 per cent 

transfer effect when the direction of rotation 

was reversed. He also noted that "the rotation 

experiment had a soothing soporific character ... " 

In a less extensive study, Mowrer (1937) 

examined the influence of vision during rotation by 12 trials alternately with and without 

fixation opportunities during rotation. Vision 

was always permitted at the stop and it was here 

that the data were obtained. He reported no 

significant evidence of habituation. 

Suzuki and Totsuka ( 1960) measured the duration of post-rotatory nystagmus during approximately 20 trials for 4 groups of subjects. 

Nystagmus was recorded from closed eyes and, 

although alertness may have been a factor in 

producing some marked trial-to-trial variability, 

no clear pattern of habituation was obtained. 

More recently, Guedry, Collins and Sheffey 

( 1961) gave experienced subjects 10 rotation 

trials per day for 5 days. Stimuli were 

14.6 ° / sec 2 for 5 sec. Odd-numbered trials were 

entirely in darkness. Even-numbered trials were 

also in darkness with the exception of a 5-sec 

period (2 sec after the stop) during which 

visual fixation was permitted. They reported a 

decline of nystagmus from day-to-day as well 

cline appeared due to an alertness factor. 

Caloric studies. In unilateral caloric studies, 

Loch and Haines ( 1946) reported that duration 

of nystagmus was unaffected when subjects were 

irrigated once daily for 5 or 6 days while wearing Frenzel glasses. However, they noted 

changes in the form of the response. Lidvall 

(1961a, b; 1962) used a small number of 

stimuli ( 4-6) and found nystagmus habituation regardless of whether the interstimulus 

intervals were short ( 6-8 minutes) or long ( 1-25 

days). Fluur and Mendel (1962a, b) reported 

reduced nystagmus from a series of 12 unilateral irrigations. In the studies of Lidvall and 

of Fluur and Mendel, eye movement recordings 

were obtained from behind closed eyes. These 

studies differ significantly from those of rotation in that the canals on one side only are 

stimulated. In this regard, Lidvall (1961b) has 

stated that diminution of responses so elicited 

"should not prove surprising" in view of recovery patterns following unilateral labyrinthectomies. 

Present results. The present data indicate 

that, when subjects are kept in an alert state, 

2b0 stimulations will not abolish nystagmus to 

a 4.1 ° j sec2 acceleration applied for 13 sec. 

That the response can disappear as a function 

of declining alertness (and be immediately reinstated by appropriate techniques) has been 

demonstrated in previous papers ( cf. Collins, 

1963a) and was evident in several of the records obtained here (Figure 11). 

Although nystagmus in the practiced direction was not abolished, the total slow-phase output and the duration of the reaction were reduced by 30.5 and 19.4 per ce~t respectively, 

from the pre-test to post-test-1. Total frequency 

declined only 3.2 per cent. However, the form 

of the response was strikingly changed. During 

the stimulus period and for a few (5-7) seconds 

thereafter, the amount of slow-phase displacement declined while the frequency of the beats 

increased. The remainder of the response became depressed for both measures and the 

duration was shorter. These data may indicate 

how an apparently complete abolishment of nystagmus occurs. Repeated elicitation of the eyemovement response may result in increased 

-17-
the fastphase of the reaction. True habituation 

in an alert subject may then come about by 

increased activity of the fast-phase center in 

interrupting the slow-phase drift of the eyes at 

earlier and earlier times so that, eventually, 

there is a very high fast-phase frequency and 

extremely little slow-phase displacement. Such 

a mechanism could, eventually, completely cancel out nystagmus. 

These data provide no indication of whether 

nystagmus is differently influenced under conditions of visual fixation. They indicate that in 

an alert subject, in total darkness, with the response permitted to run its course, nystagmus 

is not easily abolished to this mild level of 

stimulation. The previously cited studies of 

human habituation did not control for these 

factors. Thus, Griffith ( 1920b; 1924), Holsopple (1923; 1924), and Mowrer (1937) all obtained their data under conditions of fixation. 

Although Dodge (1923) did not permit vision, 

there are indications that alertness was a factor 

and, in addition, his acceleration and deceleration responses overlapped. Declines of nystagmus obtained by Guedry, et al. ( 1961) were 

reported to be substantially affected by alertness. A similar factor may account for the 

variability obtained by Suzuki and Totsuka 

(1960). 

The reductions in response obtained in the 

present study from pre-test to post-test-1 do not 

approach the declines reported in the earlier 

studies. Further, the reduction does not have 

any striking directional specificity. Although it 

is possible that the 0.18 ° j sec2 deceleration 

stimulus was not completely sub-threshold, it 

seems unlikely that it would produce an almost 

identical amount of response decline as a 

4.1 ° / sec2 stimulus while leaving the subjective 

reaction unaffected. Further, the subjects were 

permitted to relax and close their eyes prior to 

and during the deceleration period in a further 

effort to reduce any potency of the deceleration 

stimulus. It should be noted, however, that since 

a secondary nystagmus was frequently in progress when deceleration was initiated, some 

interaction of this ongoing response with the 

deceleration stimulus might have occurred on 

some trials (see Figure 12). 

of rest, indicates that there was little, if any

recovery of the nystagmic reaction. A further 

drop in duration and slow-phase activity is evident. Frequency of nystagmus showed a sligh

overall increase. These changes were true of 

both the practiced and unpracticed directions

Hence, the changes which the repeated stimulation induced are not attributable to simple fatigue nor are they readily reinstatable. A similar permanency of change was reported by 

Griffith (1924) and Guedry et al. (1961). It is 

interesting to note that a brief (15 min) res

during a series of successive rotations resulted 

in a temporary elevation of the nystagmic response whereas a far lengthier rest-period (1 

month) had no significant restorative effect. 

The tasks. Previous short-term studies o

alertness and vestibular function (Collins

1962; Collins, Crampton & Posner, 1961) indicated that timing tasks could lose their attentionvalue. Several records obtained here showed 

wandering eye-movements or dysrhythmia dur

ing response periods while subjects were making temporal estimations. However, the subject

were extremely well motivated and such occur

rences were remarkably few. 

It is of interest that the 2 mental arithmetic 

(MA) trials inserted at the conclusion of the 

tenth and final habituation session did not re

store nystagmus to its original level (Figure

4 and 6). This indicates that differences in 

output level between pre- and post-tests and the 

habituation series (Figure 5) can not be ac

credited solely to differences in task. It seem

clear that MA is an extremely effective mean

of eliciting a vigorous, long-duration nystagmu

to both angular acceleration (Collins, 1962

Collins & Poe, 1962) and caloric irrigation 

(Collins, Guedry & Posner, 1962). However

the major difference between the pre-test output

level and that for the habituation series seem

due to the rapid decline of nystagmus which 

occurs within the first few trials. Remaining 

differences appear attributable to (a) a mor

vigorous response during MA and subjectiv

rotation tasks, and (b) fewer pre- and post-tes

trials. 

-18-
frequently reported, sharp decline of nystagmus 

from trial-to-trial (e.g., Griffith, 1920b; Guedry et aL 1961). That some such reduction in 

response occurred is clear, but as Figure 7 

illustrates, it is remarkably slight, is greatest 

from the first to the second trial, and is at least 

temporarily reinstatable by a few minutes of 

rest (Trial 11). Figures 8, 9, and 10 illustrate, 

with the exception of the first session, that the 

pattern is not at all a regular one and the within-session declines are generally not great in 

alert subjects. 

Some comparative data. Nystagmus habituation has been demonstrated for a number of 

infrahuman species. Repeated vestibular stimulation under a variety of conditions has produced marked response declines in the pigeon 

(Fearing, 1926; Mowrer, 1934), the squab 

(King, 1926), leghorns (Fukuda, Hinoki & 

Tokita, 1958), white rats (Griffith, 1920a), 

rabbits (Dunlap, 1925; Maxwell, Burke & Reston, 1922, Hood & Pfaltz, 1954), and cats 

(Collins, 1963b, c; Crampton, 1962a, b; 

Crampton & Schwam, 1961; Henriksson, Fernandez & Kohut, 1961; Henriksson, Kohut & 

Fernandez, 1961 ) . 

The present data may be compared with results obtained from a group of 10 cats exposed 

to one session of 15 unidirectional rotations 

under acceleration conditions identical to those 

reported here (Collins, 1963c) . The cat shows 

a marked and rapid nystagmus habituation. 

Initially, its response is shorter in duration and 

lower in frequency than that of man. Within a 

series of 15 trials, duration declines by about 

50 per cent and frequency and slow-phase output each by about 70 per cent. The habituation 

occurs even when alerting stimuli are introduced (Crampton, 1962a; Crampton & Schwam, 1961 ). Further, the character of the 

habituation process seems different from that 

of man. There appears to be simply an overall 

depression of activity with the maximum loss 

of response occurring after termination of 

stimulation. Crampton ( 1963) has referred to 

this as a "tailoring" of the eat's response to 

the stimulus. Other data indicate that nystagmus habituation in the cat is directionally specific (Collins, 1963b; Crampton, 1962a; Henriksson, Kohut & Fernandez, 1961). 

Earlier findings. Griffith ( 1920b) in addition to his reports of nystagmus decline, noted 

attenuation in the sensation of apparent motion 

which followed cessation of rotatory stimulation. Under his test conditions, visual fixation 

was permitted. 

Hallpike and Hood (1953) and Hood (1960) 

reported a directionally specific decline in the 

duration of the rotatory sensation elicited from 

subjects with closed eyes. Their technique differed from the usual stimulating conditions in 

that they applied a standard test stimulus (e.g., 

4 ° / sec2 for 6 sec) before and after a prolonged (e.g., 2 ° j sec2 for 75 sec), constant 

angular acceleration. The latter effected a notable decline in the post-test response when both 

stimuli deflected the cupula in the same direction. When the post-test caused a cupula deflection in the opposite direction, responses 

were normaL 

Guedry, Collins & Sheffey ( 1961) had subjects estimate subjective velocity during a 5-day 

test series of 10 daily trials. Trials were alternately: (a) in total darkness, and (b) in total 

darkness with the exception of a 5-sec period 

in illumination with opportunities for visual 

fixation. The average total subjective displacement dropped by approximately 50 per cent 

when tests given 1 day before and 1 day after 

the habituation trials were compared. An additional post-test 9 days later showed recovery 

such that the amount of subjective displacement 

rose from 1/ 2 to 2/ 3 of its original leveL 

Lidvall (l961a, b) reported declines in both 

the intensity and duration of the rotational experience actuated by repeated unilateral caloric 

irrigation. However not all subjects are able to 

specify a directional component to the subjective experiences occasioned by such stimulation 

(Preber, 1958). 

Subjective aspects of rotation have been frequently studied in terms of the oculogyral illusion i.e., the apparent motion of an object 

(usually a spot of light in an otherwise darkened room) which is actually in a fixed position 

relative to the subject; the object appears to 

move in lJ. definite sequence during vestibular 

stimulation. van Dishoeck, Spoor, and Nijhoff 

(1954) and Vogelsang (1961) have related the 

illusion to sensation rather than nystagmus. 

-19-
gy

as a result of a series of stimulations in total 

darkness, although a similar series with the 

target light present, and a third series with room 

illumination resulted in marked declines. Guedry ( 1950) found a trial-to-trial attenuation in 

the duration of the illusion by alternating trials 

in total darkness with those in full-room illumination. Later, he reported declines in duration 

of the illusion which were specific to the direction of nystagmus when room illumination was 

introduced (Guedry, 1953a, b). These studies 

emphasized the importance of visual fixation 

in habituation of the OGI response. 

In a later study, Guedry and Ceran (1959) 

employed prolonged, constant angular accelerations of low magnitudes. Although their primary concern was in the decline of subjective 

velocity (using a target light as a reference 

point) during an extended stimulus period, they 

also noted a reduction in subjective velocity 

as a function of stimulus repetition. The reduction of the subjective response during a 

single prolonged stimulus (Guedry & Beberman, 1957; Guedry, Cramer & Koella, 1958; 

Guedry & Lauver, 1961) represents an adaptation process which probably differs from that 

under consideration here. 

Present results. The data obtained for subjective rotatory experiences provide a clear 

indication that the decline in the sensation of 

angular movement is specific to a practiced direction of stimulation. The 200 CW habituation 

trials produced virtually no change in the magnitude and duration of the subjective reactions 

to CCW acceleration. However, for the practiced direction, total subjective displacement 

declined by about 37 per cent, and peak subjective velocity by about 39 per cent from the 

pre-test to post-test-1. After one month without intervening rotation trials, recovery was evident. Total subjective displacement was now 

only 27.5 per cent less, and peak subjective 

velocity only 16.5 per cent less, than the pretest values. A decline in rotatory sensation with 

repetition of stimulation and a subsequent indication of recovery after several days of rest was 

also reported by Guedry, Collins & Sheffey 

(1961). 

made directionally specific and that visual fixation is not a necessary condition for such an 

occurrence, these data provide an indication 

that subjective vestibular habituation may occur 

in the absence of attending to the rotationa

stimulus. Reports from the subjects seemed to 

indicate that they were generally unaware of 

rotatory sensations during the habituation series 

and were attending, instead, to the assigned 

tasks. 

Some Related Studies 

Occupation-induced habituation. The per

formance of individuals in certain occupations 

would seem to require at least some forms o

vestibular habituation. Figure skaters, for example, undergo extremely vigorous rotatory ex

periences with no apparent disorienting effects

Examination of such people in the laboratory is 

reported to indicate a lack of both vertigo and 

nystagmus when they are stimulated either by 

rotation or by caloric irrigation (McCabe

1960). 

Since World War I, the study of vestibula

habituation has been closely related to aviation 

medical problems. Indeed, questions concern

ing the vestibular function of pilots provided 

the impetus for many of the early studies. Re

cent investigations have examined groups o

pilots to determine the effects of flying experi

ence on their responsivity to vestibular stimu

lation. Aschan ( 1954) employed rotationa

stimuli and reported lower-than-normal value

for both sensation and nystagmus durations in 

a group of Swedish fighter pilots. There was no 

apparent directional specificity for the reduced 

sensation, but directional differences in nystag

mus appeared related to the direction in which 

the pilot preferred to "roll" his plane. Long 

periods of reduced flying activity resulted in 

a "normalization" of the vestibular response

particularly with respect to nystagmus. 

Caporale and Camarda (1958) examined 4 

acrobatic jet pilots with rotation tests of nystag

mus. They noted a vestibular asymmetry in 

each pilot that was correlated with the latera

position of the man in the acrobatic V-forma

tion most frequently used. 

-20-
I 

pilots before and after flight training. He divided them into 3 groups (no airsickness; airsick once or twice; severely airsick several 

times) on the basis of a questionnaire given 

after 4-6 months in the course. In re-examining 

his vestibular findings obtained before training 

began, he noted large differences between the 

"no airsickness" and the "severely airsick" 

groups. The latter showed greater maximum 

slow-phase eye speed and longer duration of 

sensation to both rotation and caloric irrigation. 

A follow-up examination of the "severely airsick" group after they had adapted to the flying 

situation and had shown no further symptoms 

indicated that their sensations of turning and 

the maximum eye-speed of nystagmus had declined for the rotatory and caloric tests. 

Groen (1962) mentions a study by Krijger 

which indicated that both the sensation and the 

nystagmic response to rotation were inhibited 

in experienced test pilots when their data were 

compared to those of a control group. After 

several weeks of flying inactivity, their responses returned to normal. 

Observations during an aircraft maneuver 

were made by Dearnaley, Reason, and Davies 

( 1962). Subjects reported the duration of the 

vestibular after-sensation following one-minute 

long, 45-degree banks. Duration of the sensation 

was markedly shorter for experienced pilots 

than for trainees whether their eyes were closed 

or visual references were available. 

The studies cited above indicate that the repeated vestibular stimulation occasioned by 

some occupations results in a recoverable modification of the vestibular response. That the 

reduction of sensation was not found to be directionally specific ( Aschan, 1954) while that 

of nystagmus was (Aschan, 1954; Caporale & 

Camarda, 1958), and that recovery of the oculomotor reaction occurred after several weeks 

of inactivity ( Aschan, 1954; Groen, 1962) 

differ from findings in the present study. However, several reconciliating explanations are 

possible: ( 1) Only duration of the sensation 

was reported in the cited studies. Present data 

show little effect on the duration but a marked 

effect on the intensity of the subjective reaction. 

Further, the pilots were exposed to angular 

may have had an equalizing effect. (2) Habituation of the vestibular response for these occupational groups is occasioned by efforts to overcome sensations which intrude on performance. 

Further, opportunities for visual fixation are 

present. It is possible that the mechanism of 

habituation differs depending upon whether 

combinations of intention and visual references 

are present, or whether the reaction is simply 

elicited repetitively (Guedry, 1964). The latter condition may more accurately represent 

Hood and Pfaltz's ( 1954) "non-meaningful 

stimuli" than does the former. 

Unusual vestibular stimulation. Responses to 

passive rotation about the center of a vertical 

axis with the head held in a fixed position, characteristic of the test situation reported here, 

differ markedly from the vestibular reactions 

elicited as a result of head movements during 

constant rotation. The subjective experience 

produced by such stimulation can be extremely 

uncomfortable and disorienting, and the nystagmic reaction comprises both horizontal and vertical components. Habituation of these Coriolis 

phenomena, both subjective and ocular, was 

noted by Guedry and Montague ( 1961), while 

Graybiel, et al. ( 1961) reported a reduction in 

the oculogyral illusion as a result of repeated 

head movements in a rotating room. 

Analysis of Coriolis nystagmus habituation 

indicated that a compensatory response, opposite in direction to the responses elicited as a 

result of head movements in the rotating room, 

was built up over time to counteract the disorienting reactions and produce a state of 

adaptation (Guedry & Graybiel, 1962). Further 

studies indicated that, when head movements 

were restricted to a particular quadrant, there 

was no transfer to the unpracticed quadrant 

(Guedry, Graybiel & Collins, 1962; Guedry, 

Collins, & Graybiel, 1963). 

The vestibular habituation attendant to adapting to head and body movements in a constantly rotating environment appears different from 

the mechanism by which nystagmus was reduced 

in the present study. However, there are notable 

differences in the experimental conditions. In 

the Coriolis studies, all 3 pairs of semicircular 

-21-
ceptor activity was marked, visual fixation was 

permitted, and, as in the occupational studies 

cited above, intention was involved as the subjects tried to inhibit the uncomfortable reactions. 

Overview 

Data obtained in the present study indicate 

that a bidirectional decline in nystagmic output 

occurs in man as a result of repeated unidirectional angular accelerations in total darkness. 

Nystagmus, however, is not readily abolished 

to these mild levels of stimulation if subjects 

are maintained in an alert state. Rather, the 

character of the response becomes altered, apparently by increased activity of the central 

mechanism which controls the fast-phase of the 

reaction. This modification of the central nervous system is not capricious; the response 

shows little or no recovery toward its original 

intensity and form after a month of rest. 

The decline in the subjective rotatory experience has four aspects of interest. ( 1) Whereas 

nystagmus was bidirectionally modified, the reduction of the sensation of rotation was specific 

to the direction of the habituation trials. 

( 2) The reduction occurred in the absence of 

visual references. (3) The reduction apparently occurred without the attention of the subjects 

being focused on their sensations of movement. 

( 4) A pattern of recovery of subjective intensity was evident after 4 weeks with no intervening stimulation. 

It is possible, indeed even likely, that the 

reduction of the subjective reaction might have 

been greater had appropriate visual stimuli 

been employed. It has been demonstrated that 

under certain conditions, visual information can 

obviate the sensation of movement while nystagmus is relatively unaffected (Guedry, Collins & Sheffey, 1961). The present study provides additional confirmation of the separate 

nature of the oculomotor and the subjective 

aspects of the vestibular response. 

An evaluation of this and other studies ( cf. 

Crampton, 1962b) seems to indicate that no 

single term, such as "habituation," "response 

decline," "central suppression," or "adaptation," can completely connote the effects of repeated stimulation upon vestibular function. 

ation, to use the classical term, and the types 

apply to both sensation and nystagmus. 

One of these, as Wendt (1951) noted, refers 

to alertness or arousal. If a subject is not in 

an alert state, nystagmus output shows a marked 

reduction and, in some cases no nystagmus may 

be present. Such a state probably occurs with 

repetition of stimulation as the subject become

habituated to the environmental conditions in

cluding the stimulus and the novelty of the situ

ation. This type of habituation appears to in

fluence both the slow- and fast-phases of ny

stagmus, although the latter activity appear

more significantly reduced (Collins & Guedry

1962). The subject who is not alert may also 

have no subjective rotatory experience. 

Related to the above is the direction of the 

subject's attention. The present study indicate

that an alert subject need not attend to rotation 

in order to produce changes in the subjective and 

in the eye-movement responses. However, if a 

subject does a~tend to the rotational stimulus

nystagmus may decline as a function of decreas

ing subjective experiences (Guedry & Lauver

1961). In this situation, however, the reduction 

of the sensation probably results in a reduction 

in arousal with its consequent attenuation o

nystagmus. 

A second type of habituation is evident in 

the present study. Here repeated simple stimu

lation of alert subjects reduced nystagmus by 

apparently increasing the activity of the centra

mechanism controlling the fast-phase of the re

action. The subjective response was also re

duced although subjects, engrossed in their as

signed tasks, reported that they were unawar

not only of their eye-movements, but also o

the accelerations. 

A third type of vestibular habituation is th

conditioned compensatory nystagmus to Coria

lis stimulation (Guedry & Gra ybiel, 1962)

Here a complex array of sensory and volitiona

impulses are repetitively elicited and a reduc

tion of undesirable reactions occurs by mean

of a centrally produced reaction, opposite i

sign, which cancels them out. 

In addition to their theoretical implications

the present data have practical significance

The changes in vestibular reactivity as a resul

-22-
of repeated stimulation, whether by experiment

al, occupational, or avocational means, point up 

the need for caution in the clinical evaluation of 

vestibular function and in the selection and 

specification of subjects used in experimentation. The fact that directionally specific subjective modifications can occur may be worth 

considering when changes in certain occupational routines are required. Thus, for safety purposes, an individual who has habitually performed preciSion tasks involving primarily 

unidirectional vestibular input (e.g., an acrobatic crew pilot - Caporale & Camarda, 1958) , 

may require a period of practice if his routine 

is shifted so that stimulation from the opposite 

direction is incurred. 

Summary 

Ten subjects were each exposed to a habituation series of 200 CW accelerations in total 

darkness while performing a number of attention-demanding tasks. Decelerations were subthreshold. Preliminary and post-tests indicated 

that slow-phase nystagmus and duration of the 

ocular response declined bidirectionally as a 

function of the habituation trials. That the total 

reduction in response was not as great as that 

reported in earlier studies seems due to the 

task-control of alertness. A marked change in 

the form of the response occurred. Specifically, 

stimulus repetition produced an increase in frequency of nystagmus during the stimulus period 

and for a few seconds thereafter. The remaining 

"tail" of the response showed an overall depression. These changes were approximately equal 

for both CW and CCW stimulation. 

Measurements of subjective velocity were obtained during several pre- and post-test trials 

but never during the habituation series. A decline in the intensity of the sensation to CW 

acceleration was produced by the habituation 

series but the subjective experience to CCW acceleration was unaffected. Thus, a directionally 

specific decline in the subjective vestibular response occurred in the absence of attending to 

the rotatory sensation in the habituation trials 

and without visual cues. 

A second post-test given after one month 

with no intervening stimulation showed little or 

no restoration of nystagmus. However, the subjective reaction demonstrated a clear, albeit incomplete, pattern of recovery. 

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pilots. Acta Otolaryngol., Suppl. 116, 24-31. 

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Caporale, R. and Camarda, V., 1958: La funzionalita vestibolare di alcuni piloti di pattuglia acrobatica. Riv. M ed. 

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Collins, W. E., 1962: Effects of mental set upon vestibular 

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to directionally equivalent and non-equivalent stimuli 

after unilateral caloric habituation. CA Rl Report 63-14, 

Oklahoma City, Okla. 

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cat following habituation to rotation. CAR / Report 63-13, 

Oklahoma City, Okla. 

Collins, W. E. and Guedry, F. E., 1962: Arousal effects and 

nystagmus during prolonged constant angular acceleration. Acta Otolaryngol., 54, 349-362. 

Collins, W. E., Guedry, F. E., and Posner, J. B., 1962 : Control 

of caloric nystagmus by manipulating arousal and visual 

fixation distance. Ann. Oto-, Rhino-, Laryngol., 71, 

187-202. 

Collins, W. E. and Poe, R. H., 1962: Amphetamine, arousal, 

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Collins, W. E. and Posner, J. B., 1963 : Electroencephalogram 

alpha activity during mild vestibular stimulation. Nature, 

I 9 9, 933-934. 

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Crampton, G. H. and Schwam, W. ]., 1961: Effects of arousal 

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Physiol., 200, 29-33. 

Dearnaley, E. ]., Reason, J. T., and D'avies, J. D., 1962: The 

nature and duration of after-sensation following the 

cessation of turning in a Chipmunk aircraft. Aerospace 

Med., 33, 1224-1229. 

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6, 1-35. 

Dunlap, K., 1925: Adaptation of nystagmus to repeated 

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Fearing, F., 1926: Post-rotational head nystagmus in adult 

pigeons. ]. comp. Psychol., 6, 115-131. 

Fluur, E. and Mendel, L., 1962a: Habituation, efference and 

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Otolaryngol., 55, 65-80. 

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II. Combined caloric habituation. Acta Otolaryngol., 55, 

136-144. 

Fukuda, T., Hinoki, M., and Tokita, T. Static and kinetic 

labyrinthine reflex: Functional development of labyrin· 

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1958, 49, 467-477. 

-23-
p

cular canals as indicated by the oculogyral illusion. 

Aerospace Med., 32, 321-

Griffith, C. R., 1920a: The effect upon the white rat of continued bodily rotation. Amer. Naturalist, 54, 524-534. 

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Soc. Amer., 34, 1497-1503. 

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Academic Press, New York (in press). 

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Ky. 

Guedry, F. E. and Ceran, S. J., 1959: Derivation of "subjective velocity" from angular-displacement estimates made 

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Visual and other factors influencing caloric nystagmu

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effect of repeated rotation on the duration of afte

nystagmus in the rabbit. Amer. ]. Physiol., 58, 432-438. 

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upon the duration of post-rotational vestibular nystagmu

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1223. Wiley, New York. 

-24-
Trials 

1 

2 

3 

4 

5 

6 

7 

8 

Mean 

APPENDIX A 

RESPONSE SCORES FOR THE PRE- AND POST-TESTS. EAOI VALUE IS A 

MEAN FOR TEN SUBJECTS EXCEPT PRE TRIAL 1 AND POST-2 

TRIALS 1 AND 2 (NINE SUBJECTS). 

Duration (Seconds) Freg,uencl Slow-Phase (De&rees) 

Pre Post-1 Post-2 Pre Post-1 Post-2 Pre Post-1 Post-2 

53.1 39.9 34.0 66.5 60 .. 3 60.1 546 365 305 

50.2 40.1 34.3 65.7 55.9 59.6 527 387 316 

46.1 37.7 38.0 64.2 60.6 60.9 506 376 327 

49.2 42.5 38.3 65.6 63.0 63.3 475 404 376 

44.6 37.0 35.9 56.8 56.5 64.3 468 336 264 

48.0 44.9 35.2 65.7 59.2 56.3 529 393 274 

45.8 38.1 32.9 61.9 61.0 67.9 485 317 261 

44.0 37.8 32.7 65.9 58.1 66.6 516 360 274 

47.6 39.8 35.2 64.0 59.3 62.4 506 367 300 

-25-
APPENDIX B 

RESPONSE SCORES FOR 11m PRE- AND POST-TESTS. EAOI VAWE IS A MEAN 

FOR EIGHT TRIALS EXCEPT PRE- SCORES FOR RW (7 TRIALS) AND POST-2 

SCORES FOR LM (6 TRIALS). 

Sessions Subjects 

MB PB LB RB JH LM HS KS RW HW 

Mean Duration of N;rstagaus ~Seconds) 

Pre 51.4 52.4 39.6 47.5 37.3 60.6 36.4 53.5 51.1 52.9 

Post-1 41.1 41.6 39.4 33.6 32.8 46.8 27.4 40.3 44.4 49.8 

Post-2 40.8 38.0 21.7 31.8 24.8 50.0 Z9.9 41.1 41.8 47.1 

Total Slow-Phase DisElacement (Desrees) 

Pre 510 506 336 321 333 639 231 593 610 1062 

Post-1 229 437 345 211 201 577 1•88 486 259 744 

Post-2 276 282 171 238 124 516 166 350 342 660 

Total Freguenc;r of N;rstaS!us 

Pre 69.8 91.9 58.6 47.5 56.5 75.3 33.0 91.6 55.0 68.6 

Post-1 77.0 67.0 62.8 37.3 44.1 69.5 33.1 84.1 51.5 67.8 

Post-2 90.8 82.6 49.1 38.5 48.9 93.0 34.5 80.3 53.6 76.0 

Freguenc;r of N;rstagaus During First 20 Seconds 

Pre 34.0 31.0 44.3 27.6 30.6 23.8 27.1 32.1 45.5 19.1 

Post-1 52.4 40.1 42.9 33.7 34.2 25.6 28.1 32.4 53.1 26.9 

Post-2 57.2 36.1 50.1 39.3 38.7 25.7 29.9 34.1 54.0 26.3 

-26 -

U. S. GOVER NM ENT PRINT ING OFF' ICE : 1964 0-732-432 
Civil Aeromedical Research Institute, Federal Aviation Agency, Oklahoma City, Oklahoma. CARl Report 

63-29, TASK-CONTROL OF AROUSAL AND THE 

EFFECTS OF REPEATED UNIDIRECTIONAL ANGULAR ACCELERATION ON HUMAN VESTIBULAR RESPONSES by William E. Collins. 

Subjects were exposed to a 10-day habituation series of 200 

CW accelerations in total darkness while performing attentiondemanding tasks. Decelerations were sub-threshold. Preliminary and post-tests indicated that slow-phase nystagmus and 

duration of the ocular response declined bidirectionally as a 

function of the habituation trials, but frequency of nystagmus 

increased during the stimulus period and for a few seconds 

thereafter. These changes were approximately equal for both 

CW and CCW stimulation. Measurements of subjective velocity 

were obtained during several pre- and post-trials but never 

during the habituation series. A decline in the intensity of 

the sensation to CW acceleration, but not to CCW stimulation, 

was produced by the habituation series. A second post-test 

given after one month with no intervening stimulation showed 

little or no restoration of nystagmus. However, the subjective 

reaction demonstrated a clear, albeit incomplete pattern of recovery. 

Civil Aeromedical Research Institute, Federal Aviation Agency, Oklahoma City, Oklahoma. CARl Report 

63-29, TASK-CONTROL OF AROUSAL AND THE 

EFFECTS OF REPEATED UNIDIRECTIONAL ANGULAR ACCELERATION ON HUMAN VESTIBULAR RESPONSES by William E. Collins. 

Subjects were exposed to a 10-day habituation series of 200 

CW accelerations in total darkness while performing attentiondemanding tasks. Decelerations were sub-threshold. Preliminary and post-tests indicated that slow-phase nystagmus and 

duration of the ocular response declined bidirectionally as a 

function of the habituation trials, but frequency of nystagmus 

increased during the stimulus period and for a few seconds 

thereafter. These changes were approximately equal for both 

CW and CCW stimulation. Measurements of subjective velocity 

were obtained during several pre- and post-trials but never 

during the habituation series. A decline in the intensity of 

the sensation to CW acceleration, but not to CCW stimulation, 

was produced by the habituation series. A second post-test 

given after one month with no intervening stimulation showed 

little or no restoration of nystagmus. However, the subjective 

reaction demonstrated a clear, albeit incomplete pattern . of recovery. 

1. Vestibular 

Function 2. Adaptation 

3. Nystagmus 

4. Psychology 

5. Sensory 

Psychology 

1. Vestibular 

Function 2. Adaptation 

3. Nystagmus 

4. Psychology 5. Sensory 

Psychology 

Civil Aeromedical Rese

tion Agency, Oklahoma 

63-29, TASK-CONTRO

EFFECTS OF REPEAT

GULAR ACCELERAT

BULAR RESPONSES b

Subjects were exposed 

CW accelerations in tot

demanding tasks. Decel

ary and post-tests ind

duration of the ocular 

function of the habitua

increased during the s

thereafter. These chang

CW and CCW stimulati

were obtained during 

during the habituation 

the sensation to CW ac

was produced by the 

given after one month 

little or no restoration 

reaction demonstrated recovery. 

Civil Aeromedical Rese

tion Agency, Oklahoma 

63-29, TASK-CONTRO

EFFECTS OF REPEAT

GULAR ACCELERAT

BULAR RESPONSES b

Subjects were exposed 

CW accelerations in tot

demanding tasks. Decel

ary and post-tests ind

duration of the ocular 

function of the habitua

increased during the s

thereafter. These chang

CW and CCW stimulati

were obtained during 

during the habituation 

the sensation to CW ac

was produced by the 

given after one month 

little or no restoration 

reaction demonstrated recovery.