Abstract: The effects on classical fear conditioning of the rate of presentation of the unconditioned stimulus (US) and the contingency between the conditioned stimulus (CS) and the US were examined using the conditioned emotional response procedure with rats Increases in US rate reduced suppression by the same amount whether the added USs were signaled by CS, thereby maintaining the CS-US contingency, or unsignaled, thereby weakening the CS-US contingency Failure to control for the rate of US presentation in previous studies of the effect of CS-US con­ tingency on fear conditioning has led to the unsubstantiated conclusion that CS-US contin­ gency is fundamental to classical conditioning It is now widely accepted that classical conditioning depends not only on the temporal contiguity of condi­ tioned stimulus (CS) and unconditioned stimulus (US), but also on the CS-US correlation or contingency With the contiguity, or joint occurrence, of CS and US held constant, CS-US contingency is weakened either by presentations of CS alone or by presentations of US alone A commonly used index of contingency is given by the difference between conditional probabilities: the probability of US given CS, or P(US/CS), and the probability of US in the absence of CS, P(US/no CS) The contingency is positive when P(US/CS) is greater than P(US/no CS), negative when the reverse is true, and zero when the probabilities are equal Mackintosh (1974) expressed the prevailing view of the importance of contingency for conditioning when he wrote: "condi­ tioning experiments can be operationally defined as arrangements of correlations or contingencies between events The most natural interpretation is that animals detect these contingencies : exposed to these particular relationships they learn to associate these correlated events" (p 244) The results of the present experiment question this conclusion The idea that contingency is fundamental to condi­ tioning owes much to the work of Rescorla In an influential paper on the proper control for classical conditioning, Rescorla (1967) argued that only those behavioral changes that depend on CS-US contingency should be regarded as conditioned Accordingly, a noncontingent CS-US sequence is the proper control for classical conditioning, even though that sequence will generally include some contiguous presentations of

Abstract: Conditioning involved adding one flavor (e.g., vanilla) to an artificial diet of high caloric density and a second flavor (e.g., anise) to a similar low-calorie diet. When the rats were tested with identical foods to which the flavors were added, they showed a strong preference for the high-calorie flavor. The parameters of conditioning were varied in four experiments, which showed that the conditioning of taste preferences is rapid and powerful and has generality over a range of conditioned stimulus parameters. The last experiment indicated that the unconditioned stimulus for this conditioning is probably some oral cue, such as the taste of starch, which is correlated with caloric benefit, rather than caloric benefit per se.

Abstract: A series of experiments on the role of Pavlovian processes in tolerance to amphetamine-induced anorexia in rats was conducted. In Experiment 1A, tolerance to the suppressant effect of d-amphetamine (4.0 mg/kg) on milk consumption was substantially diminished in an environment not previously associated with drug administration. Experiment 1B supported the interpretation that Pavlovian compensatory conditioning rather than a nonassociative mechanism mediated this phenomenon. Experiment 2 examined the hypothesis that "contingent tolerance" results from an inadvertent manipulation of Pavlovian cues. As in previous research, tolerance was contingent in that it did not develop if the rats were not exposed to food under the influence of the drug. Tolerance developed only if access to food occurred under the influence of amphetamine, but as in Experiment 1A, it was substantially diminished in an environment not previously associated with drug administration. Thus, tolerance to amphetamine-induced anorexia was shown to be both contingent on previous experience with food in the drugged state and subject to Pavlovian control. No current explanation for the occurrence of contingent tolerance or for the control of tolerance by Pavlovian processes can at once account for both of these findings. Experiment 3 confirmed the hypothesis that interaction with the food stimulus would be necessary to extinguish tolerance. This finding is also problematic for any current behavioral theory of tolerance. It is proposed that interaction with food is necessary for the homeostatic regulation of disturbances in eating caused by amphetamine. When activated, this regulatory process operates by means of Pavlovian conditional compensatory processes.

Abstract: A series of five experiments was carried out in which fear of context caused by exposure to shocks was manipulated by signaling the shocks with a discrete stimulus, signaling the days during which shocks occurred with a session-long stimulus, or switching the context between exposure and the subsequent test. All these manipulations influenced fear of the context in the manner predicted by the Rescorla-Wagner associative model. Following this, all the rats were given conditioning trials with shock and a different discrete stimulus. All preexposure treatments produced consistent and reliable interference with conditioning with the exception of signaling the shocks with a discrete stimulus, which greatly reduced interference. These results are interpreted as being consistent both with a cognitive explanation of the US exposure effect, which claims that animals learn that shocks are unpredictable during conditioning and this knowledge retards future conditioning when they are predictable, and with an adaptation explanation, which claims that unpredictable shocks produce chronic fear and this fear through either a change in adaptation level or through emotional exhaustion renders the shocks less reinforcing during the conditioning test.

Abstract: Two experiments are reported which investigate the speed of contextual conditioning in autoshaping. In both experiments, a procedure was employed in which ring doves were magazine trained in one context prior to the manipulation of background values in a second context. In Experiment 1, subjects were exposed to 4, 8, 64, 128, or 256 US-only presentations prior to autoshaping. Acquisition speed and maintained response measures were monotonically related to the number of pretraining trials. Subjects in Group 4 acquired the key-peck response fastest, and retardation was maximal within 64 pretraining trials. In Experiment 2, subjects given 20 pretraining trials were significantly more retarded than subjects given 2 pretraining trials, but only when pretraining and testing were conducted in the same context. Overall, the results of these experiments show that in autoshaping, contextual conditioning is very rapid; this demonstrates the plausibility of theoretical accounts of Pavlovian conditioning which assert that the development of the conditioned response depends on the associative values of both the CS and background stimuli.

Abstract: Opiate agents were administered into the central nucleus of the amygdala complex of rabbits prior to either classical conditioning or pseudoconditioning of heart rate responding. Compared to control groups, opiate administration into the central nucleus did not significantly alter baseline heart rate, heart rate responding during habituation trials to presentations of the conditioned stimulus alone, or heart rate responding during the pseudoconditioning procedure. However, opiate administration altered the acquisition of a conditioned bradycardia response during classical conditioning trials in which the offset of the conditioned stimulus was coincident with the presentation of an aversive unconditioned stimulus. The opiate agonist levorphanol (5.0 nmole) significantly impaired the acquisition of the conditioned bradycardia response. This effect was observed to be stereospecific and blocked by concurrent administration of the opiate antagonist naloxone (2.5 nmole). Naloxone (2.5 nmole) administration alone significantly increased the magnitude of the conditioned bradycardia response. These effects produced by opiate administration into the central nucleus were not observed following administration of the same agents into sites 1–2 mm dorsal to the central nucleus.

Abstract: The aim of this study was to compare cardiovascular and electrodermal responses from subjects conditioned to fear-relevant stimuli with responses from phobics selected to fear the same stimuli. In the first session of the conditioning group slides of either a snake or a spider were presented. One of these served as a CS+ reinforced by an electrical shock and the other as a CS-, which was never followed by shock. In addition the conditioning group was exposed to two neutral pictures (flowers and mushrooms). The phobic group viewed the same type of stimuli and were administered some electrical shocks uncorrelated with the slides. In the second session, randomly formed halves of each group were shown (a) slides of a spider and a snake, or (b) two neutral ones. There were reliable acquisition effects in the conditioning group with the CS+ evoking larger palmar than dorsal skin conductance responses (SCRs) whereas the reverse was true for the CS-. During extinction differential responding to CS+ and CS- was maintained but palmar/dorsal differentiation disappeared. In the phobic group, feared and non-feared cues elicited differential responding with larger palmar SCRs for the feared cue only. The conditioning group failed to evidence heart rate differentiation during acquisition when all heart rate responses (HRRs) were collapsed into a single trial block (TB). When HRRs were grouped into 2 TBs, responses shifted from deceleration to CS+ on TB1 to acceleration on TB2 whereas responses to CS- were unaffected. During extinction, HR exhibited deceleration to both cues but more to CS+ than to CS-. The phobic group's heart rate accelerated to the feared cue and decelerated to the unfeared cues in both sessions. There was no difference between groups' responses to neutral cues during the second session. The results partially validate a conditioning analogue for specific phobias and the inconsistent aspects are discussed in terms of different coping strategies.

Abstract: Rabbits received bilateral microinjections of scopolamine or saline into either the dorsal hippocampus (Experiment 1) or the medial septal nucleus (Experiment 2). The animals then underwent classical conditioning of the nictitating membrane response in which a light served as a conditioned stimulus and eye shock served as the unconditioned stimulus. The results indicated that whereas hippocampal injections of scopolamine had no effect on conditioning, scopolamine injected into the medial septum retarded acquisition of the response. A third experiment indicated that this retardation of conditioning was not due to changes in sensitivity to either the conditioned or the unconditioned stimulus. The results are discussed in terms of accumulating evidence indicating that manipulations which produce certain patterns of activity in the hippocampus are detrimental to acquisition of the conditioned nictitating membrane response.

Abstract: Transfer of classical conditioning to to operant learning was demonstrated by showing enhanced acquisition of an operant discrimination in a group of rats (n=6) previously exposed to pairings of the discriminative stimulus with food as compared to control animals (n=6). A group (n=6) that received the classical conditioning sessions while under the influence of the neuroleptic, pimozide (1.0 mg/kg, IP) also showed enhanced acquisition of the discrimination when tested while undrugged but their performance was intermediate between that of the other groups for the first seven sessions. For the remaining sessions, the two groups that had received classical conditioning did not differ from each other and both groups discriminated better than the controls. These data may indicate a role for dopaminergic neurons in the mechanism by which the effects of classical conditioning influence operant responding.

Abstract: Tolerance to several effects of a number of drugs has been shown to depend on Pavlovian conditioning processes. Experiment I extended the compensatory conditioning model (Siegel 1975) to tolerance to the hypothermic effect of pentobarbital (30 mg/kg). In Experiment I, rats that acquired hypothermic tolerance in one environment did not display tolerance when tested in an environment not previously associated with drug administration. In Experiment II, rats were made tolerant to the hypothermic effect of pentobarbital (30 mg/kg) and tested for cross-tolerance to ethanol (2.5 g/kg). Cross-tolerance was observed, but it was significantly reduced if the test was in an environment different from the one in which tolerance to pentobarbital was originally acquired. Thus, the compensatory conditioning model accounts for at least part of the tolerance and crosstolerance to the thermic effects of alcohol and pentobarbital. The physiological processes in the CNS underlying tolerance and cross-tolerance for these drugs, therefore, are controlled by associative processes.

Abstract: Water-deprived male albino rats received a single presentation of a 4-sec electric-grid-shock unconditioned stimulus followed by a 4-sec white-noise conditioned stimulus (a single backward conditioning trial.) Excitation conditioned to the noise was indexed in terms of the noise’s subsequent ability to suppress ongoing licking of a water tube. The main findings were: (1) Excitation was acquired and was retained over a 30-day retention interval; (2) although excitation was retained, it did not grow significantly stronger during the interval (there was no incubation effect); (3) excitation was extinguished by noise-alone trials; and (4) excitation showed more spontaneous recovery when extinction trials were separated by 29 days than when separated by only 1 day. Because these results are similar to those in the forward conditioning literature, they seem consistent with, but do not demand, the view that forward and backward excitatory conditioning involve similar learning processes. A current theory that embraces this view is opponent-process theory (Solomon & Corbit, 1974). We suggest that opponent-process theory can (1) account for existing backward conditioning data, (2) explain the phenomenon of incubation that has previously been described in the literature while simultaneously explaining its absence in the present study, and (3) integrate certain nonmonotonic acquisition phenomena that have appeared in both the forward and backward conditioning literatures.

Abstract: In Experiment I, rats were exposed to a classical relationship between a clicker-light compound and response-independent food. Conditioning to the light was blocked if the clicker had previously served as a classical signal for food, but not if it had been established as a discriminative stimulus for food-reinforced lever pressing. In Experiment II, a tone-light compound served as a discriminative stimulus for lever pressing. Control by the light was blocked if the tone was independently trained as a discriminative stimulus, but not if it was trained as a classical signal for response-independent food. These results suggest that discriminative stimuli do not come to control appetitive instrumental responding by virtue of their implicit classical relationship to the instrumental reinforcer.

Abstract: The influence of particular stimulus properties of facial expressions of emotion upon associative learning to a neutral cue was examined in the present investigation. A compound stimulus, composed of either a fearful, happy, or neutral facial expression paired with a neutral cue (tone), signaled an aversive event (mild electric shock). Phasic change in skin conductance (SC) was used as the measure of associative learning. Analyses of variance revealed that subjects who saw a fearful expression paired with the tone gave larger SC responses to the fearful expression than to the tone. The opposite pattern was obtained for subjects who had a happy expression paired with the tone. Subjects who had the neutral expression paired with the tone showed no significant difference in their responses to the two stimuli. Results of the present investigation were consistent with those of an earlier study by Lanzetta and Orr (1980), and extend the earlier theoretical interpretations by suggesting that fear expressions function as excitatory stimuli and happy expressions act as inhibitory stimuli. Methodological changes in the present study, which include a shorter CS interval and asynchronous stimulus onsets, also extend the previous findings.

Abstract: The development of suppression in rats to a target conditioned stimulus (CS) was compared in trace and serial conditioning procedures. The interval between the end of the target CS and the shock unconditioned stimulus (US) was filled by a second CS in the serial, but not the trace, procedure. In five experiments the serial procedure produced superior conditioning. This potentiation effect, however, depended critically upon the level of conditioning to the stimulus interpolated between the target CS and the US. When conditioning to the interpolated CS was either reduced by giving independent nonreinforced trials with this CS alone or enhanced by independent reinforced trials, the potentiation effect was abolished. In addition, the insertion of a trace interval between the target and interpolated CSs reduced the effect. However, the magnitude of conditioning to the target CS was unaffected by post-conditioning changes in the conditioned strength of the interpolated CS. These findings are discussed in terms ...

Abstract: Four experiments are reported in which a stimulus (with a minimum duration of 60 s) signalling the delivery of “free” food was presented to rats lever-pressing for food available on a variable interval schedule. It was found that responding was enhanced in the presence of the stimulus when the baseline schedule of reinforcement was lean (Experiment I) and that the enhancement was dependent upon the pairing of the stimulus with free food (Experiments II and III). Experiment IV showed that an enhancement could be found after initial training in which stimulus-food pairings were given to subjects that were not concurrently lever pressing for food. It is argued that these results are consistent with the suggestion that an appetitive conditioned stimulus can energise appetitive instrumental behaviour. Department of Psychology, The University, Stirling, Scotland.

Abstract: Using a classical conditioning procedure, four groups of eight rats each were given 50 to 4,050 conditioning trials with a simultaneous tone-light compound stimulus paired with non-contingent delivery of a water dipper. The anticipatory response of entering the magazine during the CS served as the conditioned response. Following training, each group was tested in extinction such that one-third of the test trials were to the tone-light compound, one-third to the tone alone, and one-third to the light alone. Rats that had received 50 or 250 conditioning trials showed very little resistance to extinction to the light alone, whereas resistance to the tone was substantial and similar to that for the tone-light compound. After 1,250 and 4,050 conditioning trials, responding to the light increased to match the high levels of responding elicited by the tone and tone-light compound. The results present difficulties for both “continuity” and “noncontinuity” theories of stimulus selection.

Abstract: A transfer of control experiment measured the associative properties of contextual stimuli from three standard classical conditioning paradigms. After baseline training on a Sidman avoidance schedule, dogs received aversive conditioning using excitatory, inhibitory, or truly random conditioning procedures in the presence of a manipulable background stimulus. As predicted by current theory (Rescorla & Wagner, 1972; Wagner & Rescorla, 1972), the contextual stimulus was excitatory after serving as the background during conditioning of a CS− and was neutral when it had been part of the background for conditioning of a CS+. The background to the truly random procedure was also neutral. This last result contrasts with Rescorla and Wagner’s theory.

Abstract: Male and female rabbits received Pavlovian conditioning in which a 1, 216-Hz tone served as the CS and a 3-mA paraorbital electric shock train served as the US. Eyeblink (EB) and heart rate (HR) CRs were assessed. Half of the animals received prior exposure to the CS, while half were restrained in the chamber for a similar length of time but did not receive prior CS exposure. Different groups of each sex received three different CS intensities including 60, 75, and 90 dB (SPL) during both preexposure and conditioning. The results revealed that latent inhibition of the EB CR occurred only at the intermediate CS intensity, as indicated by a significant impairment of EB conditioning in this group. However, the magnitude of the decelerative HR CR was attenuated by prior CS exposure at all three CS intensities. Females showed faster EB conditioning than males, but latent inhibition occurred in both sexes. These results suggest that somatomotor and autonomic systems are affected differently by prior CS exposure.

Abstract: The theoretically appropriate means for demonstrating selective association are discussed and shown to be empirically necessary. Following the acquisition of an unsignaled instrumental avoidance baseline, dogs received either CS-contingent shocks (CS+) or random, independent CS/shock presentations. The CS was either a tone or a flashing light. When the CSs were subsequently presented during avoidance responding, only the tone-CS+ group showed absolute facilitation of response rate. However, both tone- and light-CS+ groups showed facilitation relative to their respective random controls due to the nonassociative inhibitory effects of the light. A bidirectionally sensitive dependent variable enabled the detection of this pattern of effects. Thus, a demonstration of selective association requires (1) appropriate controls for nonassociative effects and (2) selection of a dependent measure that is sensitive to both excitatory and inhibitory influences.

Abstract: In our study we examined, in the rabbit, the interactions between temperature regulation and the state of increased vigilance and emotional arousal induced by a Classical Aversive Conditioning Procedure. A Delay Conditioning Procedure was used. The Conditioned Stimulus (CS) was a 1350 Hz, 85 dB tone, the Unconditioned Stimulus (UCS) a 1 mA, 0.5 s shock. Testing sessions were run at different ambient temperatures from 5 to 30 ° C. At all ambient temperatures considered the CS induced desynchronisation of the EEG and stereotyped changes in all the autonomic variables studied. Hypothalamic temperature (Thy) first increased, then decreased below its initial value, whereas ear skin temperature (Ts) showed opposite changes. Respiratory frequency (RF) initially increased, then tended to revert to its original value. The average time course of this complex pattern was 300 s from the CS. The overall effect of the CS sequence in a session was a significant decrease in Thy and Ts and a significant increase in RF compared to control values at the beginning of the session. Both in the short (single trial) and long terms (whole session) the autonomic responses induced by the emotional stress (polypnoea and vasoconstriction) were not coherent from the point of view of thermoregulation. The hypothesis of an effect of emotional arousal in shifting set point temperatures can therefore be discarded in favour of a direct action of emotional stress on effector controllers for respiration and vasomotion.

Abstract: Two groups of rats were trained in a CER paradigm. The conditioned stimulus was a sound, the unconditioned stimulus was an electric shock. Group 1 received conventional CER training before the effects of different doses of diazepam were studied. For Group 2 the shock was always and exclusively given contingent on pretreatment with diazepam. After prolonged training the compound thus became a discriminative stimulus complex (DSC) and produced response suppression during the CS. Group 2 was also challenged with various doses of diazepam. The results showed that diazepam acquired diametrically different properties in the two groups. Group 1 exhibited disinhibitory effects and Group 2 suppressive effects, which may reflect anxiolytic and anxiogenic properties, respectively.