Sensory preconditioning and UCS inflation in human 'fear' conditioning

This study describes a human electrodermal conditioning experiment involving processes of sensory preconditioning and UCS inflation. In stage 1 of the experiment Ss received six presentations of a CS+ paired with an innocuous 65 dB tone (UCS) and six presentations of an unpaired CS-. In stage 2, Ss in the experimental group had the aversiveness of the UCS inflated as the intensity of the 65 dB tone was increased to 115 dB. In stage 3, Ss were given test presentations of CS+ and CS-. A differential CR to CS+ was found only in stage 3 of the experiment and only in Ss who had experienced the UCS inflation procedure. These results suggest that (i) sensory preconditioning had occurred in stage 1 despite the failure to observe a differential CR in this stage, and (ii) the differential CR observed in stage 3 was mediated by an internal representation of the UCS whose aversiveness had been inflated in stage 2. As well as confirming that processes of sensory preconditioning and UCS inflation can be observed in human as well as animal Ss, these findings have important implications for contemporary conditioning models of clinical fears. In particular, they suggest that a contemporary conditioning model of acquired fears is not bound by the need to discover contiguous stimulus-trauma experiences in the histories of clinical phobias since, in humans at least, processes of stimulus association and UCS revaluation appear to be relatively independent.     

The effects of cued UCS rehearsal on the retention of differential 'fear' conditioning: an experimental analogue of the 'worry' process

This study describes a human electrodermal conditioning experiment in which subjects were asked to mentally rehearse the UCS in a period following initial fear conditioning and prior to a test period involving nonreinforced presentations of the CS. Subjects who were asked to rehearse the UCS retained a differential fear CR during subsequent unreinforced presentations of the CS, but control subjects who were asked to rehearse either a nonaversive event or an aversive event unrelated to the UCS failed to retain the differential CR they had acquired during conditioning. These results suggest that rehearsal of the UCS during periods when CS and UCS are absent can aid the persistence of a fear CR in the absence of further pairings of the CS and UCS. It is argued that these effects can be explained in terms of the effect of UCS rehearsal on the strength and evaluation of the UCS representation. It is also suggested that cued UCS rehearsal might provide a useful procedure for understanding clinical incubation effects and for understanding how the 'worry' process contributes to the maintenance and incubation of fear.     

The effects of false response feedback on human 'fear' conditioning

This study describes a human electrodermal conditioning experiment in which subjects were given false skin conductance feedback during CS presentation. In comparison with appropriate attentional control groups, subjects who believed they were exhibiting a strong CR did actually emit a greater magnitude CR, while subjects who believed they were exhibiting only a weak CR emitted a significantly lower magnitude CR. When both self-report and behavioural measures of UCS revaluation were taken after conditioning, the evidence suggested that response feedback had not differentially affected subjects evaluation of the aversiveness of the UCS. The results suggest that the response modulating effects of response feedback observed in this and other studies are not caused by response feedback influencing evaluation of the UCS, but they are consistent with the hypothesis that beliefs about the nature of response feedback influence the strength of the UCS representation itself.     

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.     

UCS revaluation and conditioning models of acquired fears

Recent developments in the study of Pavlovian conditioning in humans have suggested that the strength of a conditioned response (CR) is affected not only by associative processes that link the conditioned stimulus (CS) with the unconditioned stimulus (UCS), but also by processes which lead the individual to revalue the UCS itself. These latter processes can frequently lead to dramatic changes in CR strength independently of any experience with the CS-UCS contingency. This paper discusses a number of ways in which UCS revaluation can be effected in human subjects, and discusses their implications for conditioning models of acquired fears.     

The influence of context and UCS intensity on the UCS preexposure effect in a flavor aversion paradigm

Three studies were conducted to evaluate the influence of environmental context and UCS preexposure intensity on the acquisition of a flavor aversion. In the first study, rats were exposed to two UCS-alone presentations at one of three dose levels of LiCl. The rats were given the two UCS preexposures in one of two contexts (familiar or novel). Following the UCS-alone treatment, all of the subjects received two pairings of sucrose and LiCl (1.25 meq) in the familiar context. Animals receiving UCS preexposures in the same context as used during conditioning consumed significantly more sucrose than did saline control animals. In contrast, the influence of prior UCS preexposure was not evident when UCS preexposure was experienced in a context different from that experienced during conditioning. In Experiment 2, all animal received UCS preexposure and conditioning in the novel room. Animals received either two or four preexposures at 0, 1.25, or 3.75 meq dose of LiCl. Two UCS preexposures at 3.75 meq dose produced a stronger UCS preexposure effect than did the 1.25 meq dose. Animals in Experiment 3 received two exposures to either 0-, 1.25-, or 3.75-meq LiCl in one of two contexts, followed by conditioning with the 1.25-meq LiCl dose in the same context as preexposure. Greater UCS interference occurred in animals preexposed to LiCl in the novel rather than familiar environment, with no specific dose effects in either context. These observations are discussed in terms of context blocking and generalization decrement models of the UCS preexposure effect.     

The influence of psychoticism and extraversion on classical eyelid conditioning using a paraorbital shock UCS

An experiment is described in which the effects of Psychoticism and Extraversion on classical eyelid conditioning were examined using a balanced design involving two levels of paraorbital shock intensity and two levels of response threshold. Questionnaire measures of Anxiety and Impulsivity were also analysed together with subjective ratings of the UCS. Results were broadly consistent with Eysenck's personality theory in that subjects scoring high on Psychoticism demonstrated lower levels of conditioning.     

Effects of UCS intensity and postpeak acquisition trials on classical conditioning of the SCR

The present study examined the effects of UCS intensity and number of postpeak acquisition trials on classical conditioning and extinction of the SCR. A 2 × 3 design was employed in which subjects received either a 1, 2, or 4 mA shock UCS and either two or 16 acquisition trials beyond the peak CR. While conditioning was demonstrated during acquisition, there was no relationship between strength of conditioning and intensity of UCS. The phenomenon of stronger resistance to extinction following fewer acquisition trials (e.g., two past the peak CR) than with many (e.g., 16 past the peak CR) was demonstrated only for the groups that were conditioned with the 4 mA UCS. Resistance to extinction varied positively with UCS intensity, but only for the subjects who received two postpeak acquisition trials. Sixteen trials beyond the peak CR resulted in the UCS intensity having little or no effect on resistance to extinction.     

The law of effect and CR contingent modification of the UCS

A persistent theoretical contention in the American conditioning literature is that Conditional Reflexes (CR) are reinforced through some hidden Thorndikian law of effect. In its most general form, law of effect theories hold that Conditional Reflex-Unconditional Stimulus (UCS) overlap modifies the sensory consequences of the UCS to provide the source of differential reinforcement of CRs. However, consideration of the historical development of law of effect theories reveals they have lacked testability due to the fact that the sources of reinforcement have been alleged to beintrinsically related to the occurrence and topography of CRs. Such a postulated intrinsic relationship has made it difficult to experimentally manipulate the amount of CR-correlated reinforcement, since the source of reinforcement is presumed to be under The Subject’s (S’s) control. Some experiments will be reported in which the relation between CRs and properties of the UCS are madeextrinsic and, accordingly, permit an experimental assessment of law of effect formulations.     

The effects of postconditioning revaluation of CS1 and UCS following pavlovian second-order electrodermal conditioning in humans

An experiment is described which uses various inferential post-conditioning revaluation techniques in order to clarify the associative substructure underlying Pavlovian electrodermal conditioning in human subjects. This study established a second-order skin conductance response (SCR) by pairing a CS₁ with an aversive 115 dB tone (UCS), and then pairing a different stimulus (CS₂) with CS₁. The second-order SCR survived post-conditioning extinction of the response to CS₁, but was abolished when (i) a post-conditioning habituation procedure resulted in a favourable revaluation of the tone UCS, or (ii) when subjects were given instructions which informed them that there would be no more UCS presentations. These results suggest that in the second-order electrodermal conditioning paradigm described, CR₂ is not mediated by S-R links--as it appears to be in second-order aversive conditioning in nonhuman animals--but is affected by manipulations which modify the subject's cognitions concerning the UCS.