Learned fear of "unseen" faces after Pavlovian, observational, and instructed fear

This study compared fear learning acquired through direct experience (Pavlovian conditioning) and fear learning acquired without direct experience via either observation or verbal instruction. We examined whether these three types of learning yielded differential responses to conditioned stimuli (CS+) that were presented unmasked (available to explicit awareness) or masked (not available to explicit awareness). In the Pavlovian group, the CS+ was paired with a mild shock, whereas the observational-learning group learned through observing the emotional expression of a confederate receiving shocks paired with the CS+. The instructed-learning group was told that the CS+ predicted a shock. The three groups demonstrated similar levels of learning as measured by the skin conductance response to unmasked stimuli. As in previous studies, participants also displayed a significant learning response to masked stimuli following Pavlovian conditioning. However, whereas the observational-learning group also showed this effect, the instructed-learning group did not.     

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.     

Effects of contextual conditioning and unconditional stimulus presentation on performance in appetitive conditioning

Four experiments with rat subjects examined the effects of contextual conditioning on conditioned appetitive performance. Experiment 1 compared the effects of contextual conditioning on performance to conditioned stimuli (CSs) with different conditioning histories. Contextual conditioning enhanced performance to the CS if the CS had first been conditioned and then extinguished, but had no effect on performance when the CS had been merely paired or unpaired with food. Experiments 2 and 3 then asked whether the effect on the extinguished CS was due to contextual conditioning acting as a cue for conditioning. In Experiment 2, extinction procedures in which extra unconditioned stimuli (USs) were presented during the intertrial intervals were found to reduce the CS's sensitivity to enhancement by contextual conditioning, but had no effect on spontaneous recovery. In Experiment 3, USs added to conditioning or extinction acquired the ability to cue the corresponding performance. Under some conditions, USs added to conditioning could suppress performance (Experiment 4). The results suggest that contextual conditioning has complex effects that can be better understood by recognizing that contextual conditioning, as well as the USs that create it,Mayacquire discriminative control over conditioned responding.     

Analyzing the random control procedure: Effects of paired and unpaired CSs and USs on autoshaping the chick's key peck with heat reinforcement

A series of five experiments using a total of 264 subjects investigated the effects of paired and unpaired key light (CS) and heat (US) stimuli on autoshaping the chick's key peck. Experiment 1 established that paired presentations of CS and US promoted a more rapid rise in key pecking than did randomly presented CSs and USs and that the specific sequence of stimuli under the random control procedure affected key pecking performance. Experiment 2 used a trace conditioning procedure to determine the role of the CS-US interval on autoshaping and to define empirically unpaired CSs and USs. Key pecking declined as the trace delay interval was increased from 0 to 25 sec; at 25 sec, no conditioning of key pecking occurred. Experiments 3–5 assessed the effects on autoshaped key pecking of (a) number of daily CS-US pairings, (b) added unpaired CS presentations, and (c) added unpaired US presentations, since paired and random control schedules differed in all of these respects. Reduction in the number of CS-US pairings slowed the acquisition of key pecking as did the concurrent addition of nonreinforced CSs and unsignaled USs. These results support theories of association formation that stress the effects of both paired and unpaired CSs and USs.     

Medial auditory thalamic input to the lateral pontine nuclei is necessary for auditory eyeblink conditioning

Auditory and visual conditioned stimulus (CS) pathways for eyeblink conditioning were investigated with reversible inactivation of the medial (MPN) or lateral (LPN) pontine nuclei. In Experiment 1, Long-Evans rats were given three phases of eyeblink conditioning. Phase 1 consisted of three training sessions with electrical stimulation of the medial auditory thalamic nuclei (MATN) paired with a periorbital shock unconditioned stimulus (US). An additional session was given with a muscimol (0.5 μL, 10 mM) or saline infusion targeting the LPN followed by a recovery session with no infusions. The same training and testing sequence was then repeated with either a tone or light CS in phases 2 and 3 (counterbalanced). Experiment 2 consisted of the same training as Experiment 1 except that muscimol or saline was infused in the MPN during the retention tests. Muscimol infusions targeting the LPN severely impaired retention of eyeblink conditioned responses (CRs) to the MATN stimulation and tone CSs but only partially reduced CR percentage to the light CS. Muscimol infusions that targeted the MPN had a larger effect on CR retention to the light CS relative to MATN stimulation or tone CSs. The results provide evidence that the auditory CS pathway necessary for delay eyeblink conditioning includes the MATN-LPN projection and the visual CS pathway includes the MPN.     

I like it because I said that I like it: evaluative conditioning effects can be based on stimulus-response learning

Evaluative conditioning (EC) effects are often assumed to be based on a learned mental link between the CS (conditioned stimulus) and the US (unconditioned stimulus). We demonstrate that this link is not the only one that can underlie EC effects, but that if evaluative responses are actually given during the learning phase also a direct link between the CS and an evaluative response-a CS-ER link-can be learned and lead to EC effects. In Experiment 1, CSs were paired with USs and participants were asked to evaluate the pairs during the conditioning phase. Resulting EC effects were unaffected by a later revaluation of the USs, suggesting that these EC effects can be attributed to CS-ER learning rather than to CS-US learning. Experiment 2 replicated Experiment 1 with the difference that no evaluative responses were given during the learning phase. EC effects in this study were influenced by US revaluation, suggesting that these EC effects are mainly based on CS-US learning. In Experiment 3, it was shown that EC effects can be found even if the USs are entirely removed from the procedure and the CSs are only paired with enforced evaluative responses. Together the experiments show that the valence of a stimulus can change because of a contingency with an evaluative response. (PsycINFO Database Record (c) 2011 APA, all rights reserved).     

Contextual control over conditioned responding in an extinction paradigm

Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.     

Effects of long- and variable-duration signals for food on activity,instrumental responding,and eating

Incentive-motivation theories typically assume that the conditioning of appetitive motivation involves the same parameters as Pavlovian salivary conditioning. In contrast, the Soltysik-Konorski model asserts that drive is inhibited by stimuli closely associated with food (salivary CSs) and augmented by stimuli more loosely associated with food (long and variable CS-US interval). Experiment 1 examined this latter proposition. Sixty-four rats were given extensive exposure to each of four environmental CSs, two while hungry and two while satiated. Within each deprivation condition, food was given 30–300 sec after placement of the rats in one environment, and was not given in the other environment. Performance on three separate measures—activity, lever-pressing, and food consumption—was higher in the environments previously associated with food. Experiment 2 examined the effects of discrete stimuli presented in advance of eating; in accord with the results of Experiment 1, food consumption was greater after a stimulus (1- to 9-min duration) previously paired with food than after no stimulus or after a stimulus unpaired with food. The overall results indicate (a) that stimuli associated with food become capable of facilitating a variety of food-directed behaviors, possibly via the conditioning of a common appetitive system, and (b) that a close association between the stimuli and food is not essential for such conditing to occur.     

Motivational control of second-order conditioning

Two experiments examined the motivational specificity of the associations that support 2nd-order conditioning. In the 1st phase of each experiment rats were exposed to 2 visual conditioned stimuli (CSs) paired with either a saline or food pellet unconditioned stimulus (US) prior to exposure to 2nd-order conditioning using 2 auditory CSs, 1 paired with each visual CS. Rats' motivational state was then shifted prior to a test such that if and only if specific motivational features of the 1st-order training US played a role in the 2nd-order associative structure would responding to the 2nd-order cues shift appropriately with the state change. Even when the US was irrelevant to the training motivational state, shifts in state revealed that it was encoded within the associative structure supporting 2nd-order responding.     

Pavlovian conditioning in human skilled motor behavior

The role of Pavlovian contingencies in human skilled motor behavior was investigated in three experiments by means of a new conditioning preparation. In Experiment 1 the present method was shown to be appropriate for the study of associative learning. Subjects who experienced a standard delay configuration performed significantly more conditioned responses than subjects who received either backward conditioning or random pairings. Stimulus generalization was shown to be slight in two additional groups. Subsequent experiments examined conditioning with multiple conditioned stimuli (CSs). In particular, in Experiment 2 some reciprocal overshadowing was demonstrated when two conditional stimuli (tone and vibration) were compounded. Experiment 3 investigated blocking. Blocking was less than expected, however. Subjects’ perceptions of the stimuli and reaction time data suggest that a certain proportion had shifted their attention to the added element of the CS compound. Results are discussed in relation to other studies on Pavlovian learning in humans and animals, which are concerned with “stimulus selection.”     

Changing CS features alters evaluative responses in evaluative conditioning

Evaluative conditioning (EC) refers to changes in people's evaluative responses toward initially neutral stimuli (CSs) by mere spatial and temporal contiguity with other positive or negative stimuli (USs). We investigate whether changing CS features from conditioning to evaluation also changes people's evaluative response toward these CSs. We used computer-generated male faces as CSs and paired them with other positively or negatively evaluated faces. When participants evaluated the CS faces, they either appeared unchanged, with glasses, with beards, or glasses and beards. Unchanged faces showed a clear conditioning effect, while all other face versions showed no significant conditioning effects. The conditioning effect also depended on participants’ awareness of a CS's respective US. These results mirror configural explanations of stimulus generalization in classical conditioning, with implications for EC as explanation for attitude acquisition and learning of likes and dislikes in everyday life.     

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.     

Palatability shifts in taste and flavour preference conditioning

Changes in palatability of tastes and flavours as a result of flavour preference conditioning were examined. In Experiment 1, when tastes were paired with glucose in a reverse-order differential conditioning paradigm, rats acquired conditioned preferences for CS + and displayed more hedonic responses to CS + than to CS - in a postconditioning taste reactivity test. In Experiment 2, rats that received oral infusions of flavours as CSs during a reverse-order conditioning procedure expressed both palatability shifts and conditioned preferences for CS + . Rats that received a forward conditioning procedure acquired a preference for CS + , but the palatability of CS + was unchanged. In Experiment 3, hungry rats drank mixtures of a flavour CS and a calorific or sweet tasting reinforcer in a long-exposure conditioning paradigm. When tested hungry, rats preferred CS + whether they had acquired flavour-calorie or flavour-taste associations. However, CS + became more palatable only for rats that acquired flavour-calorie associations. These results suggest that acquisition of flavour preferences, as measured by 2-bottle tests, may not always be accompanied by enhanced palatability.     

Comparison of Single Unit Responses to Tone, Light, and Compound Conditioned Stimuli during Rabbit Classical Eyeblink Conditioning

Unit recordings and lesion studies have implicated the cerebellum as an essential site for the acquisition and maintenance of the conditioned eyeblink response. The current study looked at the neural characteristics of conditioned stimulus (CS) processing in the interpositus nucleus of the cerebellum after training New Zealand white rabbits (Oryctolagus cuniculus) in one of two conditioning paradigms: (a) compound conditioning (CMP), a compound CS consisting of light and tone paired with an air puff unconditioned stimulus (US); or (b) stimulus compounding (ALT), alternating blocks of tone CS and light CS trials paired with the air puff US. Single unit responses were recorded during five sessions after the animals had reached an asymptotic level of responding. Animals were tested for behavioral and neural responses to CS alone trials that included tone alone, light alone, and compound tone-light trials. For the CMP group, the compound CS elicited 80 to 90% conditioned eyeblink responses (CRs), whereas the individual tone and light CSs elicited only 40 to 50% CRs. For the ALT group, all three CSs (tone, light, and compound) elicited very high levels of responding of at least 80% CRs. For the CMP group, there were roughly equal numbers of cells responding to all of the CSs. This includes cells that responded exclusively to one, and only one, of the three stimuli and also those cells that responded to combinations of two or more. Cells from the ALT group were far more likely to respond exclusively to only one of the CSs. Both the behavioral and physiological results suggest that the compound tone-light stimulus was processed as a distinct stimulus, separate from the component tone and light. These results are discussed in the context of multisensory processing.     

Blocking of occasion setting in feature-positive discriminations

In two experiments rats received feature-positive discrimination training in which brief conditioned stimuli (CSs) were paired with food during presentations of an extended feature stimulus, and non-reinforced in its absence. In Experiment 1 a novel feature was trained in compound with a second, pretrained feature. Acquisition of control over responding to the CS by the novel feature was blocked if the pretrained feature had also been trained in a feature-positive discrimination, compared to a group for whom the pretrained feature had been accompanied by uncorrelated presentations of CSs and food. Experiment 2 employed a within-subjects design. It demonstrated that the feature from a feature-positive discrimination with a particular CS, x, blocked acquisition of control by an added, novel feature over responding to x, compared to the control acquired by the same novel feature over a novel, CS y.     

Extinction of likes and dislikes: effects of feature-specific attention allocation

The evaluative conditioning (EC) effect refers to the change in the liking of a neutral stimulus (conditioned stimulus, CS) due to its pairing with another stimulus (unconditioned stimulus, US). We examined whether the extinction rate of the EC effect is moderated by feature-specific attention allocation. In two experiments, CSs were abstract Gabor patches varying along two orthogonal, perceptual dimensions (i.e. spatial frequency and orientation). During the acquisition phase, one of these dimensions was predictive of the valence of the USs. During the extinction phase, CSs were presented alone and participants were asked to categorise the CSs either according to their valence, the perceptual dimension that was task-relevant during the acquisition phase, or a perceptual dimension that was task-irrelevant during the acquisition phase. As predicted, explicit valence measures revealed a linear increase in the extinction rate of the EC effect as participants were encouraged to assign attention to non-evaluative stimulus information during the extinction phase. In Experiment 1, Affect Misattribution Paradigm (AMP) data mimicked this pattern of results, although the effect just missed conventional levels of significance. In Experiment 2, the AMP data revealed an increase of the EC effect if attention was focused on evaluative stimulus information. Potential mechanisms to explain these findings are discussed.     

Conditioned inhibition produced by extinction-mediated recovery from the relative stimulus validity effect: a test of acquisition and performance models of empirical retrospective revaluation

Empirical retrospective revaluation is a phenomenon of Pavlovian conditioning and human causal judgment in which posttraining changes in the conditioned response (Pavlovian task) or causal rating (causal judgment task) of a cue occurs in the absence of further training with that cue. Two experiments tested the contrasting predictions made by 2 families of models concerning retrospective revaluation effects. In a conditioned lick-suppression task, rats were given relative stimulus validity training, consisting of reinforcing a compound of conditioned stimuli (CSs) A and X and nonreinforcement of a compound of CSs B and X, which resulted in low conditioned responding to CS X. Massive posttraining extinction of CS A not only enhanced excitatory responding to CS X, but caused CS B to pass both summation (Experiment 1) and retardation (Experiment 2) tests for conditioned inhibition. The inhibitory status of CS B is predicted by the performance-focused extended comparator hypothesis (J. C. Denniston, H. I. Savastano, & R. R. Miller, 2001), but not by acquisition-focused models of empirical retrospective revaluation (e.g., A. Dickinson & J. Burke, 1996; L. J. Van Hamme & E. A. Wasserman, 1994).     

A comparison of the effects of partial reinforcement schedules using a within-subject serial autoshaping procedure

Three experiments, each using a single group of pigeons, are reported. In Experiment 1 subjects were initially trained with two stimuli, one of which was always followed by food, the other being reinforced according to a 50% partial reinforcement schedule. Subsequently a serial procedure was adopted in which an additional stimulus, C, was consistently followed by the partially reinforced CS. A second additional stimulus, A, was followed on half of its occurrences by the continuously reinforced CS, its remaining presentations being followed by nothing. The rate of autoshaped keypecking was substantially greater during A than during C. In the remaining experiments subjects received first-order conditioning with a single stimulus that was either partially (Experiment 2) or continuously (Experiment 3) reinforced. The stimuli A and C were then again introduced for serial autoshaping. Stimulus A was occasionally paired with the CS and occasionally followed by nothing, whereas stimulus C was always followed by the CS. As in Experiment 1, the rate of responding during A was greater than during C. It is proposed that one influence on the rate of autoshaped keypecking during a CS is the accuracy with which the immediate consequences of that CS are predicted.     

Associative transfer and stimulus selection in classical conditioning of the rabbit's nictitating membrane response to serial compound CSs

Four experiments were conducted to determine whether in conditioning to a serial compound, CS1-CS2-UCS, there are (a) associative mechanisms operating to extend conditioning beyond the bounds of a CS-UCS contiguity gradient and (b) stimulus selection processes acting to attenuate the potency of CS-UCS contiguity. In Experiments 1 and 2, the CS2-UCS interval was held at .35 sec while the CS1-UCS interval was varied across groups from .75 to 2.75 sec. CS1 test trials revealed substantial CR acquisition at all CS1-UCS intervals. Moreover, Experiment 2 indicated that when the contribution of cross-modal generalization from CS2 to CS1 was factored out, there still remained a substantial level of conditioning, which Experiment 3 indicated was attributable to an associative mechanism like higher-order or sensory conditioning. The observation of CR acquisition at CS1-UCS intervals of 4.75, 8.75, and 18.75 sec in Experiment 4 suggested that serial compound training yields conditioning to CSs located well beyond the single CS contiguity gradient for the rabbit's nictitating membrane response. Experiments 1 and 2 also indicated the presence of stimulus selection processes because, at the shorter CS1-UCS intervals (.75 and 1.25 sec), the levels of test-trial responding to CS2 fell below those observed to the less contiguous CS1.     

Transfer of conditioned appetitive stimuli to conditioned aversive excitatory and inhibitory stimuli

The transfer of Pavlovian appetitive stimuli to Pavlovian aversive stimuli was examined in three experiments. In Experiment 1, rats received appetitive (Ap) conditioning designed to establish a flashing-light stimulus as either a CS+, CSo, or CS? for food, or to maintain it as a novel stimulus for US-alone subjects. Then, the stimulus was employed as a signal for weak shock in conditioned-emotional-response (CER) training. Both acquisition and extinction results showed that the ApCS+ facilitated and the ApCS? retarded aversive excitatory conditioning relative to the ApCSo and US-alone controls. Experiment 2 replicated the findings of Experiment 1 with both a moderate and a severe shock in CER training. In Experiment 3, different groups received the same appetitive conditioning as before, but to a flashing-light stimulus which was then employed as a signal for no shock in CER training. The ApCS? facilitated and the ApCS+ retarded aversive inhibitory conditioning relative to ApCSo and US-alone controls. Collectively, these findings establish that, in Pavlovian conditioning, transfer of an appetitive CS to an aversive excitor or inhibitor is facilitated by maintaining the initial conditioning contingency.