The effect of change in sequential visual stimulion GSR adaptation: II, the novel stimulusas a disinhibiting stimulus

ROBERT FRIED, LIVINGSTON WELCH, MIRIAM FRIEDMAN AND SUSAN GLUCKHUNTER COLLEGE OF THE CITY UNIVERSITY OF NEW YORK 1

G5R records were obtained for 20 Ss presented with aseries of 80 stimuli (four lights alternating in apparent ran­dom sequence). Records were obtained, also, for 20 Ss ineach of two groups, using the same procedure: in Group 1, atone was substituted for one of the lights, early in the se­quence, and in Group 2, it was substituted later in the se­quence. The tone, the novel stimulus, produced significantchanges in the G5R adaptation patterns of the two groups.

In previous studies, it was shown that when humanSs were presented with a sequence of visual stimuli,differing in hue, the characteristic patterns of adap­tation of the galvanic skin response (GSR) were ob­served. When a novel stimulus, i.e., a stimulus nota part of the sequence, was introduced at a point inthe adaptation sequence, no change in the GSR patternswas noted (Fried, Korn, & Welch, 1966; Fried, Welch,& Friedman, 1966; Fried, Welch, Friedman, & Gluck,1967). The novel stimulus differed from the adaptationstimuli in hue.

It is particularly important to note that, in thestudies above, while no change in GSR adaptationpatterns were observed, virtually all Ss made spon­taneous verbal reports of the presence of the novelstimulus in the sequence. This apparent paradox, whilecasting doubt on the validity of the GSR as an indexof signal detection, requires reexamination of theproperties of "novel stimuli" as these are defined inrecent studies of the orienting response (OR) inter­pretation of GSR evocation (Berlyne, Craw, Salapatek& Lewis, 1963; Kimmel, 1964). According to theseinvestigators, stimulus differentness is the criterionfor novelty. And, it must follow that any novel stimulus,I.e., any incongruous stimulus in a series, shouldincrease the probability of a GSR.

Since hue difference was shown to meet the criterionof differentness but not of novelty, it seems essentialto determine at what point the dimensions of differ­entness and novelty intercept.

The present study is an attempt to determine whe­ther the evocation of an OR, as indicated by the GSR,depends on the incongruity rather than the different­ness criterion of stimulus novelty. And, this differencehas implications for a conditioning interpretation ofGSR adaptation.

MethodThe Method of Serial Stimuli, discussed in greater

detail elsewhere (Fried, Korn & Welch, 1966), pro-

duces rapid and reasonably persistent adaptation ofthe GSR to different visual stimuli while maintainingthe Ss attention. The four stimuli in the series werewhite, blue, green, and amber lights. As in previousstudies, each hue appeared, to the S, with an averageprobability of .25 making the series apparently randomin presentation order.

The GSR records were obtained with a custom builtpathometer, coupled to a Texas Instruments Rectiriter.Hunter timers controlled the stimulus duration (7.5 sec)and interstimulus time (.01 sec).

Sixty naive female Ss were used in the study. Therewere 20 Ss in each of the two experimental groups andin the control group. Each S was seated in a darkenedroom with GSR electrodes attached to the index andmiddle finger of the left hand. Five to 10 min wereallowed to elapse before the stimulus series was pre­sented to S and the adaptation begun.

In the control group, the four light stimuli: white,blue, green, and amber were presented until 80 stimulihad appeared. In experimental Group 1, a 400 cps tonewas presented instead of the sixth amber light, andin Group 2, it appeared instead of the eleventh amberlight. The tone was well above the threshold and could,in fact, be heard in an adjacent room. This tone, whichappeared to each S only once during the adaptationseries, is the nove I stimulus.

ResultsThe data, resistance in K-ohms during each presen­

tation of the amber light, is presented in Fig. 1. TheGSR was considered the peak within the 7.5 sec periodfollowing the amber light proper. For each S therewere 20 such readings. The amber light is arbitrarilydesignated the critical stimulus: by analogy, the CS inconditioning is designated by the E and is seldom theonly stimulus to which S is exposed.

Note the adaptation patterns occured in the controlgroup. The GSR pattern of this control group doesnot differ significantly from patterns observed in groupsin previous studies cited above, in which a red light,or no light was substituted for the 6th and Ilth amberlight. Homogeneity of trends was obtained: P(F) > .05.However, when compared with the present experimentalgroups, significant differences in trends were obtained:P(F) < .01.

DiscussionIt is quite apparent, in Fig. I, that the introduction

Perception & Psychophysics, 1967. Vol. 2 (9) Copurut ttt 1967. Fsuctionomic Press, Goleta, cout, 419

a novel stimulus whose dimensions exceed a certainquantity acts as a disinhibiting stimulus. And, sub­sequently, the disinhibition effect of the novel stimulusdelays the resumption of inhibition resulting in adap­tation patterns observed.

This interpretation of the nature of GSR adaptationalso permits explanation of the results of previousstudies cited. The fact that differences in light stimulidid not evoke GSR suggests that the reactive inhibitionoperates on a generalization gradient: Only stimulisufficiently distant from the conditioning stimuli, on thegeneralization gradient, will be disinhibiting. In theprevious studies, it may be assumed, conditioned in­hibition generalized from the white, blue, green, andamber light stimuli to the red light. In the presentstudy, these lights failed to produce generalization tothe tone.201510

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Fig. 1. GSR adaptation: mean resistance (in K-ohms) rollowingpresentation or the amber light stimulus and the novel stimulus.

of the novel stimulus disrupted the adaptation patternsof the two experimental groups. The disruptive effectis greatest in Group I, where the novel stimulus wasintroduced early in the adaptation series. This contin­uous disruption suggests something other than an orient­ing response in an otherwise fatigued attention task.That is, the OR interpretation would suggest that anovel stimulus produced a GSR, but that shortly afterthe novel stimulus, GSR adaptation proceeds at its usualpace. This clearly is not what was observed in the pre­sent study.

It is tempting to suggest the alternate hypothesisthat GSR adaptation, analogous to any psychomotortask, generates reactive inhibition (Hull, 1943) whichbecomes conditioned to the task components. Thus,

ReferencesBerlyne, D., Craw, M., Salapatek, J., & Lewis, J. Novelty, com­

plexity, incongruity, intrinsic motivation and the GSR. J. expoPsycho/., 1963, 66, 560-567.

Fried, R., Kom, S., & Welch, L. Effect of change in sequentialvisual stimuli on GSR adaptation. J. expo P suctiot., 1966, 72,325-327.

Fried, R., Welch, L., & Friedman, M. Stimulus novelty and intra­series primacy in GSR adaptation. Percept. & Psychophys., 1966,1, 345-346,

Fried, R., Welch, L., Friedman, M., & Gluck, S. Is no stimulus astimulus? J. cxp . Psuchol.; 1967,73, 145-146.

Hull, C. L. Principles oj behavior. New York: Appleton-Century­Crofts, Inc., 1943. Pp. 277-289.

Kimmel, H. D. Adaptation of the GSR under repeated applicationsof the visual stimulus. J. expo Psychol., 1964, 68, 421-422.

Note1. Also Department of Psychiatry, Cornell University MedicalCollege.

(Accepted jor publication May 9, 1967.)

420 Perception & Psychophysics, 1967, Vol. 2 (9)