Gerall & Woodward, 1958; Hilgard, Dutton, & Helmick, 1949; Hilgard, Miller,. & Ohlson, 1941; Hilgard & Ohlson, 1939; Kugelmass, Hakerem, & Mantgiaris,. 1969 ...
Perceptual and Motor Skills, 1986, 62, 315-322. @ Perceptual and Motor Skills 1986
CLASSICAL CONDITIONING OF PUPILLARY CONSTRICTION1 RICHARD L. BORREGO Denver Veterans Administration Medical Center RICK M. GARDNER Univerrity of Southern Colorado Summary.-Previous attempts to condition classically the pupillary response have resulted in mixed outcome. Srudies using light as the UCS have generally been unsuccessful while those studies using shock as the UCS have been more successful. In the present study six subjects were visually presented 15 CVC trigrams while their pupil sizes were monitored. Five of the C V G had been previously presented, five had been previously presented while paired with shock, and five had not been previously presented. Analysis indicated that more pupillary constriction occurred to the five CVG paired with shock than those presented without shock or those not previously presented. The resulting classically conditioned pupillary constriction is discussed in terms of the development of meaning through classical conditioning.
Contradictory results have been found in attempts at classical conditioning of the human pupillary response. While many of the earlier attempts reported success (Watson, 1916; Cason, 1922; Hudgins, 1933; Baker, 1938), many of the more recent studies show no pupillary conditioning (Crasilneck & McCranie, 1956; Fitzgerald & Brackbill, 1968; Gerall, Sarnpson, & Boslov, 1957; Gerall & Woodward, 1958; Hilgard, Dutton, & Helmick, 1949; Hilgard, Miller, & Ohlson, 1941; Hilgard & Ohlson, 1939; Kugelmass, Hakerem, & Mantgiaris, 1969; Steckle, 1936; Steckle & Renshaw, 1934; Wedell, Taylor, & Skolnick, 1940; Young, 1954, 1958). All of these studies used light as the UCS. In his review of the literature in this area, Voight (1968) concluded that human pupillary conditioning was not possible and that reports of previous successes could be accounted for by lack of appropriate control groups, crude methodology, and the subjective nature of response measurement. In another review Young (1958) similarly concluded that human pupillary conditioning was not possible. One possible explanation for the failure to obtain pupillary conditioning might be in the nature of the UCS used. Spence (1951) has suggested that a stimulus must have intrinsically reinforcing properties to be an effeccive UCS. Where light is used, therefore, the intensity must be very high or it will fail 'This study was partially supported by the research advisory committee at the University of Southern Colorado. The authors express their appreciation to Joseph Romero and Suchoon S. Mo for their assistance in this research. Reprint requests should be addressed to Rick M. Gardner, Department of Psychology, University of Southern Colorado, Pueblo, Colorado 81001.
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as a UCS. Gerall, et al. (1957) later suggested that shock as a UCS would meet the requirement proposed by Spence and was in fact successful using shock in conditioning the pupillary response in humans (Gerall & Woodward, 1958). Tanck ( 1970) also used shock as a UCS while Kugelmass, et al. (1967) used a sharp click in successful attempts at pupillary conditioning. Apparently the CS-UCS interval is critical in obtaining pupillary conditioning. Young (1958), using a 6-sec. interval and Gerall and Woodward ( 1958) using a .5-sec. interval were both unsuccessful in obtaining conditioning. On the other hand, Gerall, Sampson, and Boslov (1957) and G e r d and Woodward (1958) were successful using a 1.5-sec. interval. Controversy also exists regarding the direction the CR will take in pupillary conditioning. Previous studies have indicated that, when pupillary conditioning does occur, pupillaty dilation is the CR obtained. Lowenfeld (1966) states unequivocally that from a physiological point of view all psychologic and sensory stimuli, with the exception of light, dilate the pupil and none of them constrict it. This notion has received support from Janisse (1974) and Hakerem and Lidsky ( 1969). However, Hess ( 1965, 1975) has long maintained that this notion is false and cited research by himself as well as Beck (1967) and Kahneman (Kahneman & Peavler, 1969) to support the notion that pupillary constriction can and does occur to certain auditory stimuli. Hess (1965) has also demonstrated that unpleasant stimuli can induce pupillary constriction. Hess ( 1975) admits that "it is unquestionably more difficult for experimenters to obtain psychosensory pupil constrictions than psychosensory pupil dilations, particularly when dealing with pooled data rather than with responses of individual subjects" (p. 39). Hess seemingly would support the notion that pupillary conditioning is possible and that constriction could be the obtained CR, while Lowenfeld, among others, would deny this possibility. The notion of acquired meaning might be the most parsimonious explanation for conditioned pupillary constriction, were it obtained. If a neutral stimulus is paired with unpleasant stimulation such that the stimulus acquires negative affective values, then 'one might expect pupillary constriction would be the natural response in subsequent presentations of the stimulus. Such a finding would be compatible with the aversion-constriction hypothesis proposed by Hess (1965) that unpleasant visual material will cause pupillary constriction. Supporting this notion is Hall's (1976) review of heartrate conditioning literature using shock or noise as the UCS. Hall concludes chat deceleration of heartrate is the most common CR. The present study represents an attempt to obtain pupillary conditioning with a visual CS and shock as the UCS. Shock was paired with certain CVCs to determine whether pupillary conditioning would occur and, if so, whether the CR would be reflected in pupillary dilation or constriction.
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Six undergraduates, three men and three women at the University of Southern Colorado, volunteered co serve as subjects. The CS was visually presented on a Lehigh Valley Electronics human test panel located 1 meter in front of the subjects. CVCs appeared as a slightly dimmed light and were 3 cm X 3 un in size. The UCS was a 110-volt AC electric shock presented to the subject's right index finger. Pupil size was continuously monitored by a Polymetric Model No. 1165-IR pupillometer and recorded on a Hewlett-Packard Model 7101 B-12 strip chart recorder. White noise was continuously presented at 70 db to the subjects via earphones to mask extraneous sounds.
A treatment-by-treatment-by-subjects experimental design was used. Each subject was told that he was participating in a classical conditioning experiment that involved shock. The subject was then told the experimenter would slowly increase the level of shock and "when it becomes unpleasant you are to tell me, and this will be the level of shock used throughout the first part of the experiment." Each subject was encouraged to take as high a level of shock as they could tolerate. This procedure resulted in an average shock of 5 mA at 110 v AC. Each subject then placed the head in the headmount of the pupillometer and was instructed to focus on the center window of the test panel. The subject was instructed to memorize the CVCs which were to be presented in the center window. Subjects were presented 10 moderately meaningful CVCs having Archer (1960) values 40 to 60 under conditions of shock and no shock. In both conditions the 10 CVCs were sequentially presented a total of 12 times with each CVC presented for 4 sec. with no intertrial interval. Three different random sequences were used in presenting the stimuli. Five of the 10 CVCs were randomly selected and paired with shock and the remaining five were presented without shock. In the shock condition the CVC only was presented for the first 1.5 sec. and CVC paired with shock for the remaining 2.5 sec. of the interval. In the nonshock condition the CVC only appeared throughout the 4-sec. interval. Following this conditioning procedure the earphones and shock electrodes were removed and the subject was informed that they would be shown a series of 15 CVCs. During this phase the subject was presented the 5 CVCs previously paired with shock, the 5 CVCs previously presented with no shock, and 5 new CVCs of similar meaningfulness not previously presented. The 15
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CVCs were presented in a random order under the same lighting conditions as during the conditioning trials. Each CVC was presented for 10 sec. with a 10-sec. intertrial interval. Pupil size was continuously recorded during this phase of the experiment.
RESULTS AND DISCUSSION Pupil diameter per second was recorded for each subject. Disproportionately large pupil diameters are typically observed during early test trials. Woodmansee (1966) recommended that such data be disregarded as atypical. Because such atypical pupil sizes were obtained in the present experiment, the data for the first test CVC was deleted for three subjects and data for the first two test CVCs for three other subjects were also deleted. One recording of pupil size per second was made from the strip-chan recording. Mean pupil dilation each second was then calculated for each condition. The resulting functions showed large individual differences in both pupil size and variability over time. To eliminate these differences a z score transformation ( z = ( X - U ) / S , ) was applied to all subjects' raw data such that each subject's data subsequently had a mean of zero and a standard deviation of 1.0 (see Gardner, Beltramo, & Krinsky, 1975 for further elaboration and justification of this z transformation). At any given second all z scores for a given subject in all three experimental conditions will sum to zero. The resulting z scores were then averaged across seconds for all subjects. Fig. 1 displays the average z values for each condition. Also shown in Fig. 1 are three control baseline points. The control baseline points were determined by calculating the mean pupil size for each subject at Seconds 7, 8, and 9 which occurred just prior to presentation of the CVCs. Fig. 1 shows a similar pattern of pupillary response in each of the three treatments over the 10-sec. period. There was an increase in pupil size from the control baseline to 1 sec. for the exposure only and no-exposure treatments, and very little change for the shock-plus-exposure treatment. This was followed by constriction at 2 sec., slight dilation after 2 sec., and slight constriction around the last 3 sec. Fig. 1 also shows a similar magnitude of pupillary response to the exposure only and no exposed CVCs,and a much smaller pupillary response to the shock plus exposed CVCs. A two-way analysis of variance indicated that the exposure only, no exposure, and shock plus exposure conditions had a significant effect on the p u p i l l q response (FzSlo= 8.14, p .01) . No significant differences existed over seconds or in the interaction term. Tukey multiple comparison tests showed that the pupil was significantly more constricted during the shock plus exposed CVCs than during both the exposure only ( q 3 , 1 7 7 = 4.14, P < .05) and no exposure ( q 3 , 1 7 ' 1 = 5.40, p < .O5) CVCs, while no significant difference was found between the exposure-only and the nonexposed CVC.. A one-
