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.     

Avfail in color avoidance learning by starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus)

Certain unconditioned stimuli (UCS) in flavor avoidance learning sometimes become ineffective after pairings with relatively stronger UCS. This failure of avoidance learning (avfail) has been demonstrated only with rodents. The present investigations were conducted to determine whether avfail might also occur with avian species, the food selection of which is guided primarily by visual cues. In Experiment 1, starlings were given pairings of methiocarb (a relatively weak UCS) and LiCl (a relatively strong UCS). In Experiment 2, red-winged blackbirds were given pairings of two concentrations of methiocarb (relatively weak and relatively strong UCS, respectively). Pairings were followed by a conditioning trial (UCS gavage in the presence of a color cue) and two-choice tests. Conditioned avoidance was always observed except when methiocarb preceded LiCl and when the low preceded the high methiocarb dose in preconditioning pairings. Experiment 3 demonstrated that UCS habituation could not account for the results of Experiments 1 and 2. The data reflect avfail in the visual modality, and a biological implication of the results is that birds may not learn strong avoidance of aposematic prey containing varied levels of toxicant.     

Skin conductance response conditioning with CS intensities equal to and greater than UCS intensity

With .2-sec bursts of white noise as both conditioned stimulus (CS) and unconditioned stimulus (UCS), conditioning of first-interval skin conductance responses was obtained when the intensity of the CS equaled and exceeded that of the UCS. There was no evidence that second-interval response conditioning occurred. Nonspecific response frequencies were also affected by the variations in stimulus intensity, this raising some question about typical controls employed in SCR conditioning. There was some evidence that second interval responses were suppressed by the intense CS values. It was concluded that the existence of simple conditioning with a CS/UCS intensity ratio equal to or greater than unity was contrary to the Pavlovian proposition that a CS must be biologically less salient than the UCS in order for conditioning to occur. It was noted, however, that the suppression of second-interval responses might indicate that anticipatory CRs which are not confounded with orienting reflexes are prevented from exhibiting a conditioning effect when a high CS/UCS intensity ratio is employed.     

Reinstatement of fear to an extinguished conditioned stimulus.

Four experiments are reported which demonstrate the ability of an unconditioned stimulus (UCS) presentation following extinction to partially reinstate the conditioned response. These experiments are interpreted in terms of the strengthening of an extinction-reduced UCS representation. The first two experiments address alternative interpretations in terms of sensitization, reinstating the stimulus conditions of acquisition, conditioning of background cues, and stimulus generalization. Experiment 3 suggests that reinstatement is possible with a UCS qualitatively different from that used in conditioning. Experiment 4 explores an alternative extinction procedure which especially preserves the conditioned stimulus-unconditioned stimulus association while encouraging modification of the UCS representation. The results are discussed both in terms of related empirical phenomena, such as spontaneous recovery and sensory preconditioning, and in relation to the general role of the UCS representation in conditioning.     

Conditioned response-contingent delays of the unconditioned stimulus in human aversive conditioning.

Four groups of subjects were given either 0. 100, 500, or 1,000 msec delays of the unconditioned stimulus (UCS) contingent upon the occurrence of a conditioned response (CR) and were given a UCS 515 msec after conditioned stimulus (CS) onset when a CR did not occur. A fifth group received standard classical conditioning trials with an interstimulus interval of 515 msec. Overall performance decreased as CR-contingent UCS delay increased, with the classical conditioning group approximating the performance of the group receiving the 100-msec delay. The data were analyzed with the two-phase model of conditioning and the following results were obtained: The duration of Phase 1 of the model increased with contingent delay; operator limits associated with CR trials or with combined CR-CR (CR absent) trials decreased as a function of delay; and operator limits associated exclusively with CR trials were unaffected by the delay. Subjects receiving a contingent delay of 0 msec gave the shortest latency responses and exhibited reliable latency decreases across trials, suggesting an attempt to "beat" the UCS. The results were interpreted as contrary to what would be expected from low-of-effect theories which postulate that reinforcement results from a CR-UCS interaction, although they could be subsumed under a drive or an associative strength theory in which the aversive, or CR-supportive, strength of the UCS is assumed to be negatively correlated with contingent UCS delay.     

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.     

Classical heart-rate conditioning in the rat: The influence of curare and various setting operations

Conflicting reports concerning the success of classical conditioning of heart rate (HR) in curarized animals led to an experiment using a transfer design in which rats were classically conditioned either under curarized or restrained conditions. These conditions were then reversed for each group, giving a Curarized-Restrained (C-R) and a Restrained-Curarized (R-C) group. Results indicated that curare inhibits the conditional and unconditional HR response both during initial acquisition and after asymptotic levels of a HR CR have been attained. In addition, the C-R group did not acquire a CR during their later non-curarized restrained conditioning sessions, implying an inhibitory transfer from their earlier conditioning under curare. The UCRs during this period were normal for restrained rats. Analogous experimental“setting operations” prior to restrained conditioning were then explored by a second experiment which attempted to replicate the inhibitory transfer effect. The experimental operations investigated included: (1) restrained conditioning to investigate conditioned inhibition possibilities; (2) pseudo-conditioning types of randomized CS and UCS non-paired presentations to investigate associative vs. non-associative explanations; (3) CS-Only presentations to investigate possibilities that curare creates a blockage to the UCS, thus creating an inhibiting habituation to the CS; and (4) a group receiving curarization sessions, but no conditioning, to test the drug-only transfer effects. Results from the first and second experiments together indicated no inhibitory transfer effects under any prior experimental conditions except for those animals receiving classical conditioning while curarized. Only the CS-O group demonstrated any other kind of significant transfer effect; in this case a positive transfer accelerating later conditioning due to prior CS habituation sessions. These findings were discussed within the context of existing reports of curarized conditioning and setting operation effects on later conditioning, and various potential explanations and interpretations were explored.     

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.     

Conscious knowledge of CS-UCS contingency information affects extinction retrieval of conditioned disgust responses: Findings from an online de novo disgust conditioning task

ObjectiveThe present study aimed to establish and develop an online de novo conditioning paradigm for the measurement of conditioned disgust responses. We further explored the effects of explicit instructions about the CS-UCS contingency on extinction learning and retrieval of conditioned disgust responses.MethodThe study included a sample of 115 healthy participants. Geometric figures served as conditioned stimuli (CS) and disgust-evoking pictures as unconditioned stimuli (UCS). During disgust conditioning, the CS+ was paired with the UCS (66% reinforcement) and the CS- remained unpaired; during extinction and retrieval, no UCS was presented. Half of the participants (n = 54) received instructions prior to the disgust extinction stating that the UCS will not be presented anymore. 1-2 days or 7-8 days later participants performed a retrieval test. CS-UCS contingency, disgust and valence ratings were used as dependent measures.ResultsSuccessful acquisition of conditioned disgust response was observed on the level of CS-UCS contingency, disgust and valence ratings. While some decline in valence and disgust ratings during the extinction stage was observed, contingency instructions did not significantly affect extinction performance. Retrieval one week later revealed that contingency instructions increased the discrimination of the CSs.ConclusionsExtinction of conditioned disgust responses is not affected by explicit knowledge of the CS-UCS contingencies. However, contingency instructions prior to extinction seem to have a detrimental effect on long-term extinction retrieval.     

Classical conditioning of autonomic fear responses is independent of contingency awareness

The role of contingency awareness in classical conditioning experiments using human subjects is currently under debate. This study took a novel approach to manipulating contingency awareness in a differential Pavlovian conditioning paradigm. Complex sine wave gratings were used as visual conditional stimuli (CS). By manipulating the fundamental spatial frequency of the displays, we were able to construct pairs of stimuli that varied in discriminability. One group of subjects was given an "easy" discrimination, and another was exposed to a "difficult" CS+ and CS-. A 3rd group was exposed to a stimulus that was paired with the unconditional stimulus (UCS) 50% of the time and served as a control. Skin conductance response (SCR) and continuous UCS expectancy data were measured concurrently throughout the experiment. Differential UCS expectancy was found only in the easy discrimination group. Differential SCRs were found in the easy discrimination group as well as in the difficult discrimination group, but not in the 50% contingency control. The difficult discrimination group did not exhibit differential UCS expectancy but did show clear differential SCR. These observations support a dual process interpretation of classical conditioning whereby conditioning on an implicit level can occur without explicit knowledge about the contingencies. The role of contingency awareness in classical conditioning experiments using human subjects is currently under debate. This study took a novel approach to manipulating contingency awareness in a differential Pavlovian conditioning paradigm. Complex sine wave gratings were used as visual conditional stimuli (CS). By manipulating the fundamental spatial frequency of the displays, we were able to construct pairs of stimuli that varied in discriminability. One group of subjects was given an "easy" discrimination, and another was exposed to a "difficult" CS+ and CS-. A 3rd group was exposed to a stimulus that was paired with the unconditional stimulus (UCS) 50% of the time and served as a control. Skin conductance response (SCR) and continuous UCS expectancy data were measured concurrently throughout the experiment. Differential UCS expectancy was found only in the easy discrimination group. Differential SCRs were found in the easy discrimination group as well as in the difficult discrimination group, but not in the 50% contingency control. The difficult discrimination group did not exhibit differential UCS expectancy but did show clear differential SCR. These observations support a dual process interpretation of classical conditioning whereby conditioning on an implicit level can occur without explicit knowledge about the contingencies.     

Aversive CS control of instrumental avoidance as a function of selected parameters and method of Pavlovian conditioning

Effects of aversive CSs upon dogs' instrumental avoidance responding were assessed as a function of the Pavlovian conditioning parameters using off-baseline (Experiment 1) and on-baseline (Experiment 2) conditioning procedures. In each experiment, three UCS intensitites (2, 6, and 10 mA) were crossed factorially with two CS-UCS intervals (10 and 90 sec) yielding six groups. After 4 days of conditioning, the CS-produced effects on avoidance were determined primarily by an interaction between Pavlovian procedure (off- versus on-baseline) and UCS intensity. With off-baseline conditioning, CS-produced facilitation of avoidance was an increasing function of the UCS intensity. However, with on-baseline conditioning, only the CS paired with weak UCS facilitated avoidance, and the CS paired with the strong UCS suppressed responding. This reversing parametric function poses problems for two-process motivational theories of avoidance.     

对体液免疫反应的条件反射性调节

以饮糖精水作为条件刺激(conditioned stimulus,CS),腹腔注射免疫抑制剂环磷酰胺作为非条件刺激(unconditioned stimulus,UCS)训练Wistar大鼠,3天后腹腔注射卵清蛋白(ovalbunfin,OVA)抗原,观察再次单独条件刺激对原发性体液免疫反应的作用。结果发现．一次CU-UCS结合训练导致CS组大鼠对再现糖精水产生厌恶反应,外周血中抗OVA-IgG抗体水平显著低于UCS组。两次CS-UCS结合训练并多次给予条件刺激后,CS组大鼠抗OVA-IgG的条件性免疫抑制效应与一次CS-UCS结合训练及再次给予一次条件刺激的反应类同。这些结果证明条件刺激增强了环磷酰胺对动物原发性体液免疫反应的抑制作用．这种条件性体液免疫抑制作用是相对稳定和有限度的,不易受条件反射建立参数的影响。     

Blocking and sensory preconditioning effects in morphine analgesic tolerance: Support for a pavlovian conditioning model of drug tolerance

Two experiments on rats tested predictions of a Pavlovian conditioning model of drug tolerance which holds that tolerance is the result of compensatory conditioned responses, developed to environmental stimuli accompanying the drug administrations, which attenuate the direct effects of the drug. In Experiment I, the acquisition of tolerance-modulating properties by the tone component of a tone-light compound stimulus which accompanied morphine administrations was reduced by prior light-morphine pairings (blocking). In Experiment II, a tone stimulus acquired tolerance-modulating properties through prior pairings with a light stimulus which later accompanied morphine administrations (sensory preconditioning). These findings are uniquely predicted by the Pavlovian conditioning model of drug tolerance and are incompatible with traditional theories which assign no role to environmental stimuli present at the time of drug administration.     

The effect of UCS inflation and deflation procedures on 'fear' conditioning

Davey (1992: Classical conditioning and the acquisition of human fears and phobias: a review and synthesis of the literature. Advances in Behaviour Research and Therapy, 14, 29-66) hypothesized that subjective revaluation of an unconditioned stimulus (UCS) would determine the strength of the autonomic conditioned response (CR) in the fear conditioning paradigm. The purpose of the present study was to examine the effect of UCS aversiveness on the CR strength in the fear conditioning paradigm. The UCS aversiveness was controlled by the UCS intensity; that is, the UCS intensity was increased for the inflation group or decreased for the deflation group. Thirty subjects were randomly assigned to the inflation or the deflation group, and they participated under both experimental and control conditions. All subjects went through the pretest, the acquisition of classical conditioning, the UCS intensity operation, and the test sessions. The indices of the CR were skin conductance responses (SCRs) and a subjective aversion to the conditioned stimulus (CS). The main results were as follows. (1) The CR strength measured by SCR was increased by the UCS inflation and decreased by the UCS deflation. (2) The subjective aversiveness of the CS was not sensitive to both manipulations of UCS intensity. These results suggested that the autonomic CR strength might be influenced by the subjective revaluation of UCS, as Davey (1992) described. The result from the test of the subjective aversiveness of the CS, however, could not support Davey's model. The difference between expressions of the SCR and the subjective aversiveness of the CS might be caused by different learning systems.     

"Pseudoconditioned" jaw movements of the rabbit reflect associations conditioned to contextual background cues.

Two experiments employing 180 rabbits and involving tone conditioned stimuli (CSs) and intraoral water unconditioned stimuli (UCSs) investigated pseudoconditioning of jaw movement. CS-alone, UCS-alone, paired CS-UCS, and four explicitly unpaired CS-UCS treatments were compared to no stimulus presentation. UCS-alone presentations were sufficient to produce pseudo-CR (conditioned response) acquisition. Pseudo-CRs were retained and gradually extinguished over 30 days of CS-alone presentations. Random sequences of unpaired CSc and UCSs produced higher pseudo-CR frequencies than fixed sequences. A pseudo-CR partial reinforcement extinction effect was observed. Background extinction, that is, simply confining the subject in the experimental environment without stimulation, was effective in extinguishing both pseudo-CRs and CRs. Pseudo-CR results could not be attributed to CS-UCS trace conditioning, sensory preconditioning, second-order conditioning, or intra-analyzer conditioning. Results indicate that the associative mechanisms underlying pseudoconditioning phenomena involve conditioning of associations to contextual background (apparatus, trace, temporal, and sequential aftereffect) cues by UCS-alone and unpaired UCS presentations.     

The effects of language conditioning on various aspects of anxiety

Staats' three-function learning theory provides the basis for investigating the effects of emotionally-relevant self-verbalizations (SV) on the physiological, subjective-affective and behavioural aspects of anxiety. Using aversive electric UCSs and slides of snakes (CS), anxiety was classically conditioned in 88 volunteer Ss. In 20 subsequent language-conditioning trials (without aversive electric UCSs), the same snakes slides were paired with UCS verbalizations having either positive or negative connotative meanings. Half of the Ss were exposed to a living snake prior to language conditioning. The results show a complete extinction of the conditioned anxiety response in groups with positive SV whereas negative SV impeded extinction; the latter effect could only be found in groups without exposure to snakes prior to language conditioning. In general, the affective evaluation of snakes improved in groups with positive SV and deteriorated in groups with negative SV. However, these effects were more pronounced in groups without exposure to snakes. Although the results indicate that Ss in all groups with positive SV exhibited more approach behaviours than Ss with negative SV, this trend was not statistically significant. The possible relevance of the results for a language-conditioning approach to anxiety reduction is briefly discussed.     

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.     

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 role of awareness in delay and trace fear conditioning in humans

Expression of conditional fear without awareness has been previously demonstrated during delay conditioning, a procedure in which the conditioned stimulus (CS) and unconditioned stimulus (UCS) overlap. However, less is known about the role of awareness in trace fear conditioning, where an interval of time separates the CS and UCS. The present study assessed skin conductance response (SCR) and UCS expectancy during delay and trace conditioning. UCS predictability was varied on a trial-bytrial basis by presenting perithreshold auditory CSs. Differential UCS expectancies were demonstrated only on perceived delay and trace trials. Learning-related SCRs were observed during both perceived and unperceived delay CSs. In contrast, differential SCRs were demonstrated only for perceived trace CSs. These data suggest that awareness is necessary for conditional responding during trace, but not delay, fear conditioning.     

Under what conditions can human affective conditioning occur without contingency awareness? Test of the evaluative conditioning paradigm

The role of conscious cognitive processes in human affective conditioning remains controversial, with several theories arguing that such conditioning can occur without awareness of the conditioned stimulus (CS)-unconditioned stimulus (UCS) contingency. One specific type of affective conditioning in which unaware conditioning is said to occur is "evaluative conditioning." The present experiment tested the role of contingency awareness by embedding an evaluative conditioning paradigm in a distracting masking task while obtaining, in addition to subjective ratings of affect, both psychophysiological (skin conductance and startle eyeblink) and indirect behavioral (affective priming) measures of conditioning, along with a trial-by-trial measure of awareness from 55 college student participants. Aware participants showed conditioning with all of the measures; unaware participants failed to show conditioning with all measures. The behavioral, neurophysiological, and therapeutic implications of these findings are discussed.