Effects of extraneous stimulation on afterimage adaptation

Acta Psychologica 35 (1971) 138-150; 0 North-Holland Publishing Company

Not to be reproduced in 8x1~formwithoutwrittenpermission fromthe publisher

RFFECTS

OF EXTRANEOUS AFTERIlMAGE

GUDMUND

STIMULATION

ADAPTATION

ON

*

J. W. SMITH, LENA SJOHOLM and ALF L. ANDERSSON Lund

University,

Sweden

ABSTRACT Projected afterimages (AI) were measured serially with respect to size, intenbefore sity, and color. It was predicted that an acoustic signal administered completion of the adaptive AI process would cause (1) disruption of ongoing trends, (2) regression to initial trends, (3) prolongation of the adaptive process, and (4) at least some defensive reactions. These predictions were substantiated in a group of 28 subjects compared with a control group of 28. In a second experiment where the signal was administered late in the AI series, only few &ects were observed.

1. INTRODUCTION It has long been known that afterimages can change as a result of extraneous stimulation. Some of the early German investigators (e.g. BUSSE, 1920) reported color reversals from negative to positive hues; these they interpreted as signs of a latent propensity to eidetic imagery in their young subjects. Other authors, not of the Jaensch school, noted either disappearance of color or no change whatever and were more doubtful concerning the interpretation of their findings (LIEFMANN, 1928; GROSS, 1929). It is difficu’lt to judge the extent to which differences in the choice of experimental parameters and subjects may have accounted for differences in results. Recent research on arousal, however, suggests that the effect of extraneous. stimulation upon afterimages may be quite marked (cf. also JOHNSONand KLINTMAN, 1964). Series of experiments have shown that new stimulation influences the nervous system in a way similar to direct electrical stimulation of the reticular formation, resulting in desynchronization of EEG, fast low-voltage activity, and other signs of general activation. This arousal reaction implies that relaxed wake* The present investigation was made possible Social Science Research Council. 138

by a grant from the Swedish

EXTRANEOUS STIMULATIONON AFTERIMAGEADAPTATION 139 fulness is changed towards increased alertness (cf. LANSING et al., 1959). Sokolov and other Russian experimenters use the term orienting reflex to represent a reaction to new stimulation which ensures optimum conditions for perception of the stimulus. They have also demonstrated that when an orienting reflex is extinguished by repetitive stimulation, extraneous stimulation can cause it to reappear (SOKOLOV, 1963). In our own studies of projected visual afterimages, we have also used repetitive stimulation. Our main intention has been to trace the adaptation of an AI to the physical world outside (projection screen, measuring device, etc.), the AI being produced 15-,20 times by the subject’s fixation of a brightly colored stimulus (distance = a) and projected each time on a screen (distance = 1.5~). The earliest stages in such an adaptive process have been conceived of as characterized by a non-specific action readiness or tuning (orienting reflex), whereas in later stages, wakefulness becomes more and more relaxed as specialized functions (habits) take over an ever-increasing portion of the adaptive task. If this general description of the afterimage process is correct where other terms may of course be substituted for the somewhat ambiguous ones used above -- an acoustic signal administered when part of the adaptive process has run its course should (1) lead to a regression, a return to afterimage stages and process trends encountered prior to the signal, possibly close to the start of the experiment. As a consequence, (2) the adaptation should be prolonged. Other, less common effects might involve (3) the arousal of anxiety resulting in defensive reactions. However, (4) if the signal was delayed until the AI process had become more stabilized its effect would probably diminish. 2. EXPERIMENT 1 2.1.

Method

The AI uppanatus has been described in previous papers (cf. FRIES and SMITH, 1970). It consists of a semitransparent ground Plexiglas screen, 23.5 X 18.0 cm, movable along two horizontal bars. Two markers at the front of the screen can be moved independently of each other by means of two levers. The subject pulls the levers towards himself to measure the width of the AI. The stimulus was projected from behind the screen, the subject

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viewing it through a tight&ting eyepiece. The room was faintly illuminated (about 1.4 lux at the screen). The stimulus was a relatively intense (approx. 40 lux) red figure with straight sides and with rounded contours at the top and bottom. It had two eyes and a sad mouth schematically drawn in black (concerning the choice of stimulus, see Fries and Smith, 1970). A black fixation point coincided with a nose. The width of the stimulus was 5.5 cm. The subject fixated it for 20 sec. The fixation distance was 39 cm and the projection distance 59 cm. The expected Emmert size of the AI was thus 8.3 cm. The brightness of the AI was judged on a ten-point scale. To guide this intensity estimate, a light and a dark field were exposed on the screen before the red oval was shown. These fields served as anchor points and were called 1 (light) and 10 (dark). The subject also described the color of each AI. In order to extinguish the AI, a diffuse red light was exposed for 5 set after each trial. Twenty trials comprised a series. The time required per trial was about 70 sec. A spiral aftereflect (SAE) apparatus was also used (cf. ANDERSON et al., 1970). It permitted successive exposure of two stimulus configurations in the same visual field. The stimulus inducing the aftereffect was a thin (1 mm) black spiral line (2.5 turns arithmetic and 12 mm diameter) which rotated at a speed of 100 rpm. The subject hated the black central point of the apparently contracting spiral from a distance of 95 cm. After 45 set, the spiral was replaced by a thin (2 mm) circle, 6 cm in diameter. When the subject reported that this projection stimulus had ceased approaching him or growing, the spiral was again introduced and the next trial begun (massed trials). Two introductory trials were completed about 30 min before the 20 main trials. The subjects wore earphones in both experiments. 2.2. Design Subjects completed both experiments, but signals were administered in only one of them for each subject. The SAE introductory trials were given first, followed by the AI experiment and then the SAE experiment. The signal (pitch about 800) was sounded through the earphones during the last 3 set of fixating the inducing stimulus. Its loudness was adjusted so as to be just slightly uncomfortable to the subject.

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After about 16 measurements, an afterimage is generally reasonably well stabilized and process trends disappear. The first signal in the AI-signal was given well befure this stabilization point, at the 8th trial. Subsequent signals came at the 12th, 16th, and 20th trials. In SAE, the signal was first sounded at the 11th trial, a stage when SAE stabilization has usually already begun. The SAE results will be used here mainly as criteria when establishing the final signal and non-signal AI groups. 2.3.

Subjects

Eighty-six subjects were tested, 44 in the situation with signals in AI and 42 in the situation without (the signal being given in SAE). Twenty-three subjects with more or less incomplete protocols were discarded. Since AI and SAE results have been shown to correlate (SMITH et al., 1969) we used results from the SAE to balance the AI signal and non-signal groups. A convenient measure tried before was the mean value of the last two SAE measures (trials 9 and 10) before the signal phase. Subjects were students from introductory psychology courses and mild cases from a psychiatric clinic. We aimed at having our experimental groups as similar as possible with regard to the proportion of the normal and clinical categories and also with regard to sex and age. The final groups of 28 subjects each differed minimally with respect to the SAE criterion. The proportion of clinical cases was 9/28 in the signal group and 8/28 in the non-signal group. The distribution over age classes 25, 26-35, and 1 36 yr was 20-4-4 (12 men) in the signal group, and 16-8-4 (16 men) in the non-signal group. 2.4.

Results

How should the signal elects best be disclosed? In previous studies we had obtained useful information about AI serials by describing them as sequences of positive or/and negative trends. Another advantage of these trend descriptions is that they are easy to handle and are guided by established practice. Size as well as intensity data must be included. They have been shown to correlate only slightly, but change in one dimension is probably substituted readily enough for change in the other. Previously, when comparing trends in SAE and AI serials, substantial correlations were obtained only when the size and intensity dimensions were considered jointly (Smith et al., 1969).

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In order to establish trends in AI serials, consecutive differences between trials have to be calculated (l-2, 2-3, etc.), for both size measurements and intensity estimates. As size differences < 0.3 cm and intensity differences < 1.0 had previously been found unreliable, these were scored as zero-differences. Larger increases than those from one trial to the next were marked as plus-differences and larger decreases as minus-differences. The median number of non-zero diierences was 8-9 in the size dimension and 2-3 in the intensity dimension. Size differences therefore dominate the joint size-intensity series obtained for the subjects - size differences also being the more reliable data. The &al trend description of an AI serial implies a simple addition of signs for change in both dimensions. IIf a subject’s first four size differences were, e.g., + + 0 - and the corresponding intensity differences 0 - + 0, the joint sequence was recorded as _C 0 + -; i.e. 0 and + average to +, etc. The mathematics may seem somewhat crude but, as we shall see, they serve our initial descriptive purpose quite satisfactorily. For more precise predictions of the signal effect a more differentiated quantification of trends will be attempted later in the paper. The main hypothesis (1) formulated in the introduction requires a comparison between trends following the signal and trends in the immediate beginning of the AI serial. Such a comparison may be based on a determination of the dominant sign after the signal and a subsequent search for similar signs early in the serial. The reversed procedure will also be tried; it is particularly suited for precise predictions. A more direct description of the expected signal effect would be to compare trends immediately before and after the signal. We also presumed (2) that the signal would prolong directed trend variation in the AI serial, i.e. postpone its stabilization by forcing it to start again from the beginning. The present trend analysis allows this prediction to be tested. Color reports, linally, will serve as a means for establishing defensive reactions to the signal (3). To begin with, we thus determined the dominant (most frequent) nonzero sign in the section immediately following the signal, i.e. for the dBerences 7-9. If no sign was dominant here, we noted the earliest nonzero sign in this section. We then located the earliest occurrence of this same sign in the entire AI sequence or, in case the differences 7-9 were all zero, we found the beginning of the first series of at least

EXTRANEOUS STIMULATION

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3 consecutive zeros. Table 1 shows that this same (counterpart) sign appears at the very beginning of the experiment in most signal subjects, but only later, or not at all, in most of the non-signal subjects.

The earliest

counterpart

TABLE 1 to the sign dominating

Counterpart

the differences

in stage

Group

1

2-3

4-6

Not found

Signal Nonsignal

16

6

2

4

12

4

9

12

3

24

Comparison:

7-9

B

l/the rest; ~2 = 11.2, p < 0.0005 (one-sided).

The other way of showing whether the first signal is likely to cause a repetition of the initial AI trend was to begin by establishing the sign dominating differences l-3. Single and double zeros were disregarded; when an unbroken series of plus or minus signs extended beyond the third difference, these were then considered the dominant sign. A subject with the markings - 0 + + 0 - was thus viewed as having a dominant plus sign. Zero was scored if the tist three differences were all zero. In case no nonzero sign was more numerous than its opposite in l-3, the earliest sign counted. As is shown in table 2, the sign dominating the first part of the AI serial reappears at or soon after the signal phase more frequently in the signal than in the non-signal group. TABLE 2 to the sign dominating

The earliest counterpart

Counterpart Later 9-10

Group

7-g

Signal Nonsignal

18

7

9

8

Comparison:

differences

1-3 after the first signal,

in stage Not found

2

3

0

10

8

3

19

7-g/the rest; x2 = 5.8, p < 0.01 (one-sided).

A concomitant effect of the signal should be a disruption of ongoing trends. To test this we noted whether the llrst signs on opposite sides of the signal phase were similar or dissimilar, single and double zeros

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being disregarded. Three difference measurements in each direction were considered in order to allow zero-trends (cf. above) to appear. A series of - + 0 (signal) + - 0 meant similarity, but - + 0 (signal) - + +, dissimilarity. Zero-trends (three zeros) on each side also meant similarity. As expected, continuity (similarity), although present in about half of the non-signal subjects, was found in few of the signal subjects (table 3). TABLE

Sign similarity

on opposite

3 sides of the tirst signal.

Similar

Dissimilar B

Zero

Group

Plus

Signal Nonsignal

2

4

0

6

22

9

3

3

15

13

Comparison:

Minus

Similar/dissimilar;

~2 = 6.2, p < 0.02.

We had also predicted that directed trend variation would be prolonged as a result of the signals. ‘In previous studies a ‘directed trend had been delined as at least two similar ,signs (+ or -) with nothing more than two zeros between them. Trend marking was continued until trial 16 (15th difference), where the adaptive process had usually ceased in previous (non-signal) samples. After that stage, trends due to fatigue, etc., may well occur but are not the concern of the present study. Considering that about half of the differences are zero, a trend could scarcely be established until three or four steps after the signal phase. This explains the cutting point chosen in table 4. The results show that trend variation is prolonged by the signal. TABLE 4 of last trend within difference

Termination

Trend termination Group

O-6

7-9

Signal Nonsignal

11

0

14

7

Comparison

2

stages 1-15.

at stage 10-12

13-1.5

B

11

8

9

I7

21

3

4

7

0-9lthe rest; ~2 = 7.3, p < 0.005 (one-sided).

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These positive results tempted us to try to make the more precise predictions of the signal effect already mentioned. However, such predictions had to be based on more differentiated data. The successive differences, for S and I respectively, were therefore distributed in 9 stanine-type classes. In view of the actual distributions, the S classes were assigned numbers from + 4 to - 4 and I classes numbers from 3 (with the three middle classes counted as zero). The two +3 todimensions were added, S still remaining dominant. Within the first 6 S + I differences preceding the signal, the strongest trend was marked by means of a maximizing technique, implying that successive differences were included until a positive or negative maximum had been reached and retained through changes > 1. Negative change could, for instance, be included in a positive trend if the negative change did not lead the curve below its initial level. In case of two similar trends, the earlier was counted. Six differences I 1 constituted a zero trend; otherwise these “small differences were ignored. Table 5 presents the rather self-evident principles for calling the TABLE 5 Trend positions. Trend in l-6

Number of subjects Sign.

Compared to differences

Non-sign.

Early: beginning l-2, ending not later than 3

7

7

7-8

Intermediate: 1-4, 2-4, 2-5

9

6

8-9

Late: beginning 3 or later, ending 4 or later

6

9

9-10

Long: at least 5 dflerences

6

6

7-10

3,

trend position e&y, intermediate, late, or long. Depending on its position, a trend should be compared with the relevant section after the tit signal (but before the second one). In this section, the domi-

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G. J. W. SMITH ET AL.

nant figure was decisive. Two + 1 or - 1 could also be added. When scoring 7-10 we had to consider this section as a counterpart to the long initial trends. Thus, if there were two dominant figures with different signs, the entire sum decided the scoring; and zero-trend was scored if 1 was the largest number and the sum was < 2. The prediction of change after the first signal with regard to trend position was successful (table 6, ihustrated in fig. 1). EfIrb -----

2,3,4

4,51,6

--_---_-_

Intermediate

',9

'3~9

Sums of consecutive

Lilts <

9,lO

1132

Long

12,13

t3,14

diffarances.

Fig. 1. Smoothed-out average difference curves within the signal experiment 1 (differences in subjects with dominant negative trends

group in inverted).

Those who did not react in the predicted way after the first signal were proportionally distributed over the four types of trends. If one signal had been insufhcient to elicit their response, these subjects could be expected to react to the second signal, instead. Since trends are usually abbreviated towards the end of AI series the reactions would probably concern a smaller number of phases. Two successive differences were included. In order to increase the hit probability, we did not count difference 11 if it was zero but took 12-13 instead. Position can no longer be relevant, nor the rule that an earlier sign should dominate a later. A zero-trend could be scored only over all four differences (11-14).

EXTRANEOUS STIMULATIONON AFTERIMAGEADAPTATION 147 TABLE 6 Comparison with reference dominating differences

to position of trend 1-6 and 7-10. Dissimilarity

Similarity

Group Plus trend Signal Non-signal

12 6

Comparison!

B

Minus trend 6 0

10

18 6

~2 = 10.5, p < 0.0005

22

(one-sided).

Those subjects who did not respond after the first signal with a repetition of their dominant initial trend apparently reacted in the predicted way to the second signal (table 7). TABLE 7 Comparison between the initial trend and the dominant reaction after the second signal. Group

Signal Non-signal Comparison:

Similar 7-10 After the second signal Similar Dissimilar 9 2 p = 0.0112

9 4 (Fisher’s

Dissimilar 7-10 After the second signal Similar Dissimilar 9 9

1 13

exact test, one-sided).

In the color dimension we looked for such predicted color changes as had previously been associated with defensive reactions against anxiety. There were 7 subjects in the signal group with either more reports of red or red-violet ,(3 subjects) or of pure green (4 subjects) in phases 8-11 than in 4-7 against only 1 subject in the non-signal group (~~2 = 3.6, p < 0.05, one-sided). An attempt to establish individual differences in reactions to the signal by grouping subjects according to their SAE results was on the whole unrewarding. 3. EXPERIMENT 2 In experiment 1 the signal was given at the 8th trial, which was well before stabilization of the AI series usually occurs. This strategy

G.

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implied that we expected more insignificant reactions if the signal phase was moved to a later stage of the series (hypothesis 4). In the present experiment, we administered the first signal at the 14th trial and the second one at the 18’th. As we could hardly extend the rather exhausting AI test by more than 2 trials (22 in all) and still wanted to have enough data after the first and second signals for calculations, a later placement seemed impossible. We tested two groups of 21 subjects each, which resembled as closely as possible the groups used in experiment 1. About two-thirds of them were students from introductory psychology courses and onethird mild cases from a psychiatric clinic. As the signal was given earlier in SAE for the non-signal AI group, the matching of the nonsignal and signal groups had to be slightly changed. It now concerned initial SAE level (sum of trials 1 and 2) instead of final level. Medians and ranges differed minimally between the groups. All computations and comparisons made in experiment 1 were repeated. In most instances, hardly any trend in the same direction could be seen. Only when doing the same exact prediction as summarized in table 6 did we encounter a slight tendency at correlation (P < 0.10). 3.1.

conclusions

There can be no reasonable doubt that the afterimage series of most subjects were affected by the &-St signal in experiment 1. Ongoing trends were disrupted, and most subjects seemed to return to initial trends. It was even ‘possible, based on the position of the initial trend, to predict more exactly where a similar trend would appear after the first signal. Reactions to the second signal were observed in subjects who did not react in the expected way to the first one. As extraneous stimulation of the type administered in the present experiment must obviously lead to an arousal reaction, and as a close affinity was shown to exist between the reaction following the signal and that in the early stages of the afterimage process, it is fair to conclude that, on the whole, our previous description of these early stages, as being characterized by a nonspecific tuning is correct. Since the signal obviously forces the afterimage process to regress and start again, stabilization of it should be delayed, and it was in the present data. The disappearance of all correlations in experiment 2 was predicted. Some caution would be advisable on this point because only occa-

EXTRANEOUS STIMULATIONON AFTERIMAGEADAPTATION 149 sionally do the differences between the two experiments (predicted contra unpredicted outcomes) reach acceptable probability levels. But the results cannot be entirely ignored. For the time being, we want to make the tentative supposition that the effect of extraneous stimulation diminishes the farther from its initial tuning stage an AI process proceeds; i.e. the more dominated it becomes by specialized adaptive functions, the more ‘mechanized’ and resistant to ,disrupting stimulation it should also become. This presumption is supported by similar experiments with the oculo-gyral illusion, i.e. the illusion a subject encounters after rotation, of a stable light fixated in darkness moving. NILSEON (1970) found no effect of sound stimulation. Similarly, the SAE data in experiment 1 did not yield any clear differences between the signal and non-signal groups. In both these experiments, the first signal was given after process stabilization had occurred. A further, tentative conclusion may also be drawn from the present results. Previous studies have ascertained the diagnostic significance of early process stages in particular (SMITH et al., 1969; FRIES and SMITH, 1970). If, by administering an extraneous stimulus the early phase of the process can be at least partially reinstated, the chances of diagnostic signs appearing will increase. The process prolongation itself is still another important consequence for clinical studies in the administration of an acoustic signal, as are any additional defensive measures likely to be mobilized by an arousal reaction. (Accepted October

19, 1970.)

REFERENCES ANDERSSON, A. L., INGRIDFRIES and G. .I. W. SMITH, 1970. Change

in afterimage and spiral aftereffect serials due to anxiety caused by subliminal threat. Scandinaviun Journal of Psychology 11, 7-16. BIJSSE, PAULA, 1920. Uber die Gediichtnisstufen und ihre Beziehung mm Aufbau der Wahrnehmungswelt. Zeitschrijt jiir Psychologie 84, l-66. FRIES, INGIUDand G. J. W. SMITH, 1970. The influence of physiognomic stimulus properties on afterimage adaptation. Perceptual & Motor Skills 31, 267-271. GROSS, J., 1929. Experimentelle Untersuchungen tiber den Integrationsgrad bei Kindem, l-2. Zeitschrijt jib Angewandte Psychologie 33, 185-246, 358-387.

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JOHNSON,G. and H. KLINTMAN, 1964. Binocular rivalry as &ected by simultaneous auditory stimulation. Psychological Research Bulletin Lund Univ. 4, no. 10. LANSING,R. W., E. SCHWARTZand D. B. LINDSLEY, 1959. Reaction time and EEG activation under alerted and nonalerted conditions. Journal of Experimental

Psychology

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1-l.

LIEFMANN, ELSE, 1928. Untersuchungen iiber die eidetische Veranlagung von Schillerinnen einer hdheren Madchenschule. Zeitschrift fiir Angewandte Psychologie, Beiheft 43, 115-196. NILSSON, A., 1970. Den perceptuella efter&ect-processen och individen som biologiskt system. Lund (mimeographed). SMITH, G. J. W., INGRIDFRIES and A. L. ANDRRSSON, 1969. Individual consistencies in adaptation to negative afterimages and spiral aftereffects. Perceptual

& Motor -

Skills 28, 167-775.

and J. RIED, 1969. Diagnostic exploitation of measures in a moderately depressive patient group. Psychological Research Bulletin Lund Univ. 9, no. 6. SOKOLOV,YE. N., 1963. Perception and the conditioned reflex. New York: Pergamon. -t

visual afterdect