Simultaneous classical conditioning of two effector systems

The experiment reported here was an attempt to develop an experimental procedure for independent classical conditioning of two different response systems, the skin conductance response (SCR) and the eyelid response. In a differential conditioning design with human subjects (N = 50) two different unconditioned stimuli were used, a white noise (US1) and airpuff (US2). Two conditioned stimuli (CS11 and CS12) were paired with US1, and two other CSs (CS21 and CS22) were paired with US2. A special trial architecture was used to accomplish measurement of both anticipatory SCR and eyelid responses during each trial. Significant eyelid differentiation as well as significant SCR (especially second interval responses) differentiation developed.     

Human classical conditioning

Recent reports of failure to obtain blocking in human galvanic skin response (GSR) conditioning, together with our own equivocal results with eyelid conditioning, have motivated us to re-examine the status of the conditioned stimulus (CS) in human conditioning studies. The issues raised by compound stimuli, by contextual cues and occasion setting stimuli, and by cross-modal transfer are considered in the light of data from our laboratories. These data include observations on the interchangeability of stimulus modalities during acquisition, the use of varying information loads embedded in occasion setting displays, the comparison of alternative blocking designs and the analysis of response topography in relation to stimulus variability. They suggested that an adequate account of the CS in human conditioning studies must recognize that it is dynamically processed and reprocessed both during and after acquisition.     

Implicit attitude formation through classical conditioning

We sought to demonstrate that attitudes can develop through implicit covariation detection in a new classical conditioning paradigm. In two experiments purportedly about surveillance and vigilance, participants viewed several hundred randomly presented words and images interspersed with critical pairings of valenced unconditioned stimuli (USs) with novel conditioned stimuli (CSs). Attitudes toward the novel objects were influenced by the paired USs: In a surprise evaluation task, the CS paired with positive items was evaluated more positively than the CS paired with negative items. This attitudinal conditioning effect was found using both an explicit measure (Experiments 1 and 2) and an implicit measure (Experiment 2). In a covariation estimation task involving the stimuli presented in the conditioning procedure, participants displayed no explicit memory for the pairings.     

Differentiation between vicarious instigation and classical conditioning of electrodermal responses

In past research of vicarious conditioning when a conditioned stimulus (CS) was repeatedly presented both to a model and an observer, the observer's reaction to the CS may have been the result of a vicariously conditioned reaction to the CS, as well as a vicariously instigated reaction to the inferred emotional state of the model who anticipates the reception of a noxious stimulus when the CS is presented. In order to partial out these two reactions, the present experiment employed 32 subjects of both sexes who took part in a two-group study of differential, vicarious classical conditioning of skin conductance responses. In one of the group, the tones serving as CS+ and CS- and which preceded the aversive and non aversive events to the mode, were presented over earphones to both the confederate model and the observer subject. In the second group, only the subjects had earphones on and were led to believe that the model was not aware of the CS presentations. This eliminated the possibility of vicariously instigated reactions. Although the conditioning effects produced in the present study were somewhat weak, results clearly showed equal levels of vicarious instigation and conditioning in the two groups. These results indicate that the potential confounding of these two reactions studies has not significantly affected result or conclusions from previous studies.     

Human classical conditioning. The status of the CS

Recent reports of failure to obtain blocking in human galvanic skin response (GSR) conditioning, together with our own equivocal results with eyelid conditioning, have motivated us to re-examine the status of the conditioned stimulus (CS) in human conditioning studies. The issues raised by compound stimuli, by contextual cues and occasion setting stimuli, and by cross-modal transfer are considered in the light of data from our laboratories. These data include observations on the interchangeability of stimulus modalities during acquisition, the use of varying information loads embedded in occasion setting displays, the comparison of alternative blocking designs and the analysis of response topography in relation to stimulus variability. They suggested that an adequate account of the CS in human conditioning studies must recognize that it is dynamically processed and reprocessed both during and after acquisition.     

Allocation of cognitive processing capacity during human autonomic classical conditioning

In each of two experiments, allocation of cognitive processing capacity was measured in college-student subjects during autonomic discrimination classical conditioning. A 7.0-sec delay paradigm was used to establish classically conditioned responses to a reinforced visual conditioned stimulus (CS+). Electrodermal responses were the primary measures of autonomic classical conditioning. Allocation of processing capacity was measured by monitoring performance on a secondary reaction-time (RT) task. The auditory secondary-task RT signal was presented before, and 300, 500, 3500, 6500, and 7500 msec following CS onset. The RT signal was also presented following properly and improperly cued shock unconditioned stimuli (UCSs). Significant discrimination classical conditioning was obtained in both experiments. Comparison with control subjects who did not receive the RT signals indicated that the presence of the RT signals did not interfere with the development of classical conditioning. Four principal findings were obtained with the secondary-task RT measure. First, RTs to signals presented during CS+ were consistently slower than RTs to signals presented during CS-. This finding indicates that greater capacity allocation occurred during CS+ than CS- and is consistent with recent cognitive interpretations of classical conditioning. Second, the largest capacity allocation (i.e., slowing of RTs) occurred 300 msec following CS+ onset. This finding is consistent with the notion that subjects are actively processing the signal properties of the CS+ at 300 msec following CS+ onset. Third, presentation of the UCS when improperly cued (following CS-) significantly increased capacity allocation, whereas presentation of the same UCS when properly cued (following CS+) did not affect capacity allocation. These findings indicate that subjects were actively prepared for the UCS following CS+ but not following CS- and that a surprising UCS elicits greater capacity allocation than does an expected UCS. Fourth, large electrodermal responders to the CSs exhibited patterns of capacity allocation during the CSs, particularly during the CS+, different from those of small electrodermal responders. In particular, they exhibited significantly longer RTs at 300 msec after CS+ onset than did the small responders, followed by a shortening of RT at 500 msec relative to the small responders. This finding suggests that large electrodermal responders devote greater processing capacity to significant environmental stimuli than do small responders and that their processing may begin and be completed more rapidly. All in all, the data indicate the complexity of the cognitive processes that occur during human classical conditioning and the usefulness of the secondary-task technique in integrating conditioning theories and psychophysiology with cognitive psychology.     

The effectiveness of visual and gustatory conditioned stimuli in human classical aversive conditioning with electric shock

Thirty-six undergraduate volunteers, divided into three equal groups, were given electric shock while sipping a colored, unflavored solution (Group I): a flavored, colorless solution (Group 2); or a colored, flavored solution (Group 3), in order to determine whether human Ss respond differentially to visual and gustatory cues when the UCS is aversive electric shock. Using a standard classical discrimination procedure, the CS + was blue water for Group 1, citric acid solution for Group 2, and blue citric acid solution for Group 3. For all groups the CS- was plain water, which was never paired with electric shock. The dependent variables were derived from Staats' A-R-D theory: attitudinal change (A) and a performance measure of sip-size taken during conditioning trials (D) both confirmed the hypothesis that taste can be an effective CS when the UCS is shock, in contrast to results typically obtained with rats where visual but not taste cues are effective with a shock UCS.     

Extinction instead of incubation following classical aversive conditioning in dogs

Two dogs received a single paired classical conditioning trial, with tone CS and 12 mA shock US. Both dogs then showed a conditioned blood pressure increase in response to the nonreinforced CS, which extinguished with additional nonreinforced presentations. The CR showed spontaneous recovery four days later, but reextinguished with additional nonreinforced presentations. The results were interpreted as not supporting Eysenck’s theory of “incubation” following one-trial aversive conditioning. Partial support for this study was provided by Grant 28462 from the National Heart, Lung, and Blood Institute.     

Conditioned leg movement in the cat with massed trials,trace conditioning,and weak US intensity

Six male cats served as subjects in a classical conditioning experiment designed to assess the development of an overt conditioned response with experimental parameters that had been demonstrated to produce conditioning of neuro-electrical activity in immobilized cats. The subjects were physically restrained by means of an adjustable full-body cast during the experimental sessions which consisted of 75 habituation trials (light flash alone) followed by 225 trials with light and shock paired in a trace conditioning manner, and 75 additional extinction trials (light alone). The subjects were divided into two groups, and three different experimental sessions were given to each on three consecutive days. Group I received low US intensity (18 v) conditioning on the first day, high US (45–85 v) conditioning on Day 2 and pseudoconditioning on Day 3. Group II received the same sessions, but in a pseudoconditioning —high US—low US order. The results indicated that a conditioned leg movement was produced when the CS was paired in a trace conditioning fashion with either the high or low intensity shock US. The development of the conditioned leg movement across trials was found to be very similar to that of the conditioned neural activity in a previous study using comparable stimuli and procedures.     

The effect of UCS intensity in classical and avoidance GSR conditioning

This study compared GSR avoidance and yoked-control conditioning procedures. Classical conditioning at two UCS intensities was followed by extinction and, two months later, by an avoidance session. Matching of Ss was based on GSR responsiveness and classical conditioning in the first session. The strong UCS led to more rapid reduction in CR latency (due to an increase in number of Ss responding) in the first session, and there was a tendency for maximum CR magnitude to occur in fewer trials with the strong UCS. No UCS-intensity difference in level of responding to the CS or UCS was found in the first session. A greater amount of spontaneous recovery in the second session was found in the strong UCS group. The avoidance and yoked control groups did not differ in CR magnitudes, latencies, or frequencies, nor in UCR magnitudes in the second session. They did differ significantly in the rate of decline in intertriai responses, the decline being more rapid in the avoidance condition.     

External inhibition in a goldfish(carassius auratus) classical conditioning situation

Goldfish were classically conditioned with a light as the CS and shock as the US. The UR was a decrease in respiration. After 15 or 60 conditioning trials the fish were tested with novel stimuli (clicks) during the CS-US interval. High and moderate intensity novel stimuli produced a significant decrease in CRs (external inhibition) for fish with 60 conditioning trials (5.5 or 10.5 sec CS-US interval), but not fish with 15 conditioning trials. Low intensity novel stimuli produced no evidence for disinhibition (an increase in CRs). Control groups(e.g., groups with random presentations of the CS and US) showed that the external inhibition for fish with 60 conditioning trials was inhibition of a true CR.     

Extinction instead of incubation following classical aversive conditioning in dogs.

Two dogs received a single paired classical conditioning trial, with tone CS and 12 mA shock US. Both dogs then showed a conditioned blood pressure increase in response to the nonreinforced CS, which extinguished with additional nonreinforced presentations. The CR showed spontaneous recovery four days later, but reextinguished with additional nonreinforced presentations. The results were interpreted as not supporting Eysenck's theory of "incubation" following one-trial aversive conditioning.     

Fear develops to the conditioned stimulus and to the context during classical eyeblink conditioning in rats

In classical eyeblink conditioning, non-specific emotional responses to the aversive shock unconditioned stimulus (US), which are presumed to coincide with the development of fear, occur early in conditioning and precede the emergence of eyeblink responses. This twoprocess learning model was examined by concurrently measuring fear and eyeblink conditioning in the freely moving rat. Freezing served as an index of fear in animals and was measured during the inter-trial intervals in the training context and during a tone conditioned stimulus (CS) presented in a novel context. Animals that received CS-US pairings exhibited elevated levels of fear to the context and CS early in training that decreased over sessions, while eyeblink conditioned responses (CRs) developed gradually during acquisition and decreased during extinction. Random CS-US presentations produced a similar pattern of fear responses to the context and CS as paired presentations despite low eyeblink CR percentages, indicating that fear responding was decreased independent of high levels of learned eyeblink responding The results of paired training were consistent with two-process models of conditioning that postulate that early emotional responding facilitates subsequent motor learning, but measures from random control animals demonstrate that partial CS-US contingencies produce decrements in fear despite low levels of eyeblink CRs. These findings suggest, a relationship between CS-US contingency and fear levels during eyeblink conditioning, and may serve to clarify further the role that fear conditioning plays in this simple paradigm.     

Constraint, alcoholism, and electrodermal response in aversive classical conditioning and mismatch novelty paradigms

This study investigated whether low levels of the personality trait of constraint and early-onset alcoholism would be associated with deficits in aversive conditioning and smaller responses to novelty in a stimulus mismatch protocol. Personality traits (constraint and socialization) and skin conductance responses (SCRs) during conditioning and novelty paradigms were assessed in alcoholics (n=41) and non-alcoholics (n=32). The conditioning protocol involved measuring SCRs after conditioned stimuli (CS+: tones) paired with shock, CS− tones unpaired with shock, and CS+ probes unpaired with shock. The mismatch protocol involved measuring SCRs to auditory stimuli consisting of a series of 5 pure tones of the same pitch followed a shorter white noise stimulus (the novel stimulus). Contrary to the hypothesis, alcoholics did not differ from non-alcoholics in SCRs to CS+ probes or on the mismatch measure (SCR novel tone—SCR to 5^th tone). Higher levels of constraint and self-reports of fear during conditioning were associated with smaller responses to both the CS+ probes and the CS− tones as well as the mismatch measure within non-alcoholics, but not within alcoholics. In alcoholics, low constraint was associated with greater habituation to CS+ probes, and poor differential conditioning on measures of change across trials in SCR to CS+ probes and CS− stimuli. The results suggest that different processes influence levels of constraint in non-alcoholics and alcoholics. The data indicate that low constraint in non-alcoholics is associated with allocating fewer processing resources to potentially significant stimuli, rather than being associated with a specific deficit in aversive conditioning per se.     

Standard delay eyeblink classical conditioning is independent of awareness

P. F. Lovibond and D. R. Shanks (2002) suggested that all forms of classical conditioning depend on awareness of the stimulus contingencies. This article considers the available data for eyeblink classical conditioning, including data from 2 studies (R. E. Clark, J. R. Manns, & L. R. Squire, 2001; J. R. Manns, R. E. Clark, & L. R. Squire, 2001) that were completed too recently to have been considered in their review. In addition, in response to questions raised by P. F. Lovibond and D. R. Shanks, 2 new analyses of data are presented from studies published previously. The available data from humans and experimental animals provide strong evidence that delay eyeblink classical conditioning (but not trace eyeblink classical conditioning) can be acquired and retained independently of the forebrain and independently of awareness. This conclusion applies to standard conditioning paradigms; for example, to single-cue delay conditioning when a tone is used as the conditioned stimulus (CS) and to differential delay conditioning when the positive and negative conditioned stimuli (CS+ and CS-) are a tone and white noise.     

Cognitive conditioning: Imagined stimulus contiguity and the third interval conditional GSR

The effect of repeatedly imagining paired or unpaired CSs and USs on the frequency of post-CS responses during real extinction was studied. Four groups of 10 Ss first received a model tone and shock. For two of the groups the stimuli were paired (delayed conditioning paradigm). For the others the stimuli were arranged in a long trace paradigm. The Ss then received a series of commands requiring them to imagine receiving paired CSs and USs, or to imagine the events singly. Then 10 real tone extinction trials were given. The groups which received delayed conditioning model stimuli were more responsive than trace groups, and groups which had imagined paired stimuli were more responsive than their unpaired controls. Cognitively oriented explanations of these findings were discussed.     

Classical Delay Eyeblink Conditioning in in 4- and 5-Month-Old Human Infants

Abstract-Simple delay classical eyeblink conditioning, using a tone conditioned stimulus (CS) and airpuff unconditioned stimulus (US), was studied in cross-sectional samples of 4- and 5-month-old healthy, full-term infants. Infants received two identical training sessions, 1 week apart. At both ages, infants experiencing paired tones and air-puffs demonstrated successful conditioning over two sessions, relative to control subjects who had unpaired training. Conditioning was not evident, however, during the first session. Two additional groups of 5-month-olds received varied experiences during Session 1, either unpaired presentations of the CS and US or no stimulus exposure, fol-lowed by paired conditioning during Session 2. Results from these groups suggest that the higher level of conditioning observed following two sessions of paired conditioning was not the result of familiarity with the testing environment or the stimuli involved but, rather, the result of retention of associative learning not expressed during the first conditioning session.     

Effects of perceived similarity on vicarious emotional conditioning

The present experiment tested the hypothesis that perceived similarity between observers and models enhances vicarious emotional conditioning. Subjects were led to believe that they were either similar to the model in beliefs and attitudes, different from him or were given no information about him. They then underwent a vicarious classical conditioning procedure by witnessing the model express pain reactions in conjunction with a neutral stimulus. Observers developed emotional reactions to the neutral stimulus alone after seeing it paired with modeled pain expressions. Preceived similarity, however, had no significant effect on either the level of vicarious conditioning or the rate of extinction. Subjects who had no information concerning the model displayed stronger autonomic responses to the model's pain expressions, and more frequent and intense autonomic responses to the conditioned stimulus during tests for acquisition and extinction. In correlational analyses, subjects in the latter condition also yielded a significant positive relationship between self-reported arousal and vicarious emotional conditioning. The obtained findings were interpreted in terms of the emotion arousing properties of unfamiliarity.     

In vitro analog of classical conditioning of feeding behavior in aplysia

The feeding behavior of Aplysia californica can be classically conditioned using tactile stimulation of the lips as a conditioned stimulus (CS) and food as an unconditioned stimulus (US). Moreover, several neural correlates of classical conditioning have been identified. The present study extended previous work by developing an in vitro analog of classical conditioning and by investigating pairing-specific changes in neuronal and synaptic properties. The preparation consisted of the isolated cerebral and buccal ganglia. Electrical stimulation of a lip nerve (AT4) and a branch of the esophageal nerve (En2) served as the CS and US, respectively. Three protocols were used: paired, unpaired, and US alone. Only the paired protocol produced a significant increase in CS-evoked fictive feeding. At the cellular level, classical conditioning enhanced the magnitude of the CS-evoked synaptic input to pattern-initiating neuron B31/32. In addition, paired training enhanced both the magnitude of the CS-evoked synaptic input and the CS-evoked spike activity in command-like neuron CBI-2. The in vitro analog of classical conditioning reproduced all of the cellular changes that previously were identified following behavioral conditioning and has led to the identification of several new learning-related neural changes. In addition, the pairing-specific enhancement of the CS response in CBI-2 indicates that some aspects of associative plasticity may occur at the level of the cerebral sensory neurons.     

Simultaneous classical conditioning of two effector systems

The experiment reported here was an attempt to develop an experimental procedure for independent classical conditioning of two different response systems, the skin conductance response (SCR) and the eyelid response. In a differential conditioning design with human subjects (N=50) two different unconditioned stimuli were used, a white noise (US₁) and an airpuff (US₂). Two conditioned stimuli (CS₁₁ and CS₁₂) were paired with US₁, and two other CSs (CS₂₁ and CS₂₂) were paired with US₂. A special trial architecture was used to accomplish measurement of both anticipatory SCR and eyelid responses during each trial. Significant eyelid differentiation as well as significant SCR (especially second interval responses) differentiation developed.