The development of an attentional bias for angry faces following Pavlovian fear conditioning

Although it is well documented that fear responses develop following aversive Pavlovian conditioning, it is unclear whether fear learning also manifests in the form of attentional biases for fear-related stimuli. Boschen, Parker, and Neumann (Boschen, M. J., Parker, I., & Neumann, D. L. (2007). Changes in implicit associations do not occur simultaneously to Pavlovian conditioning of physiological anxiety responses. Journal of Anxiety Disorders, 21, 788-803.) showed that despite the acquisition of differential skin conductance conditioned responses to angry faces paired (CS+) and unpaired (CS−) with an aversive shock, development of implicit associations was not subsequently observed on the Implicit Association Test. In the present study, participants (N = 76) were assigned either to a Shock or NoShock group and completed a similar aversive Pavlovian conditioning procedure with angry face CS+ and CS− stimuli. Participants next completed a visual probe task in which the angry face CS+ and CS− stimuli were paired with angry face control stimuli and neutral faces. Results confirmed that differential fear conditioning was observed in the Shock group but not in the NoShock group, and that the Shock group subsequently showed a selective attentional bias for the angry face CS+ compared with the CS− and control stimuli during the visual probe task. The findings confirm the interplay between learning-based mechanisms and cognitive processes, such as attentional biases, in models of fear acquisition and have implications for treatment of the anxiety disorders.     

Reducing chronic anxiety by making the threatening event predictable: An experimental approach

Panic disorder is characterized by both specific, phased fear and generalized, chronic anxiety. Standard extinction procedures are efficient in reducing specific fear. However, methods based on human conditioning research - that are capable of reducing chronic anxiety have not yet been thoroughly investigated. This study evaluates a new way of reducing chronic anxiety by signaling aversive events (or by making them more predictable). Using an experimental approach with healthy participants, specific fear and chronic anxiety were operationalized in a within-subjects fear-potentiated startle paradigm by, respectively, conditioning to a cue by presenting predictable shocks and conditioning to a context induced by unpredictable shocks. The results clearly demonstrate that context conditioning is reduced when a discrete cue is added that predicts the onset of the aversive event. The data suggest that making unpredictable events, such as for example panic attacks, predictable, may reduce the generalized and sustained anxiety that often complicates exposure treatment.     

Implicit learning of evaluative vs. non-evaluative covariations: The role of dimension accessibility

Implicit covariation learning, the development of simple associations without awareness, has been demonstrated repeatedly along the evaluative dimension [De Houwer, J., Thomas, S., & Baeyens, F. (2001). Associative learning of likes and dislikes: A review of 25 years of research on human evaluative conditioning. Psychological Bulletin, 127, 853-869], but associations involving other dimensions appear more difficult to learn implicitly. The present research highlights the unique properties of the evaluative dimension that may predispose it to implicit learning. We provide evidence in the first experiment that implicit covariation learning occurs along the evaluative dimension, but does not spontaneously occur along non-evaluative dimensions. In Experiment 2, implicit learning along non-evaluative dimensions occurred when participants were subliminally primed with the to-be-learned dimension. In the discussion, we integrate findings from implicit evaluative conditioning research with the broader implicit learning literature.     

Learning to like or dislike by association: No need for contingency awareness

One way to learn to like or dislike a neutral target stimulus is through associations with positive or negative context stimuli. The present research investigates whether people need to be aware of the association between a target and a context stimulus (i.e., contingency aware) in order for associative learning of likes and dislikes to occur. We predicted that awareness of the association between context and target is necessary when target novelty is low, but not when target novelty is high. We conducted two experiments in which we varied target novelty and measured contingency awareness using a picture-bound recognition task. This allowed us to separately investigate evaluative conditioning for “contingency awareness” and “contingency unawareness” context–target pairs. The results show, as predicted, that awareness of the association between context and target is needed for low-novelty targets but not needed for high-novelty targets.     

Acquired Equivalence Changes Stimulus Representations

Acquired equivalence is a paradigm in which generalization is increased between two superficially dissimilar stimuli (or antecedents) that have previously been associated with similar outcomes (or consequents). Several possible mechanisms have been proposed, including changes in stimulus representations, either in the form of added associations or a change of feature salience. A different way of conceptualizing acquired equivalence is in terms of strategic inference: Confronted with a choice on which it has no evidence, the organism may infer from its history of reinforcement what the best option is, and that inference is observed as acquired equivalence. To test this account, we combined an incremental learning task with an episodic memory test. Drawings of faces were made equivalent through acquired equivalence training, and then paired with words in a list learning paradigm. When participants were asked to recognize specific face-word pairings, they confused faces more often when they had been made equivalent. This suggests that prior acquired equivalence training does influence how memories are coded. We also tested whether this change in coding reflected acquisition of new associations, as suggested by the associative mediation account, or whether stimuli become more similar through a reweighting of stimulus features, as assumed by some categorization theories. Results supported the associative mediation view. We discuss similarities between this view and exemplar theories of categorization performance.     

Constraints on enhanced extinction resulting from extinction treatment in the presence of an added excitor

Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects extinguished on the target CS alone, Experiments 1 and 2 found across a range of parameters that any appreciable effect of facilitated extinction due to the concurrent excitor was submerged by generalization decrement going from extinction to testing. In Experiment 3 we used different durations for the target and concurrent stimuli in order to discourage configuring and an ABC renewal design to increase sensitivity, and observed diminished renewal resulting from extinction in the presence of a second excitor. Our findings suggest that there are distinct limits to the observation of enhanced extinction in the presence of an excitor and identifies some of the sources of these limitations.     

Transfer of avoidance responding to a sensory preconditioned cue: Evidence for the role of S-S and R-S knowledge in avoidance learning

In avoidance learning studies, a warning signal (Sd) is directly paired with an aversive unconditioned stimulus (US) unless a particular response is performed. Research by Augustson and Dougher (1997) demonstrated that not only warning signals but also stimuli that are indirectly paired with the aversive event are capable of affecting the avoidance response. In the present study, we extended these results by incorporating a sensory preconditioning paradigm in an avoidance learning procedure. Sensory preconditioning training influenced the selection of avoidance responses in the presence of warning signals that were never paired directly with the aversive events. Moreover, results suggest that the selection of the avoidance responses was based on an integration of knowledge about the relation between the Sd and the US (S-S knowledge) and knowledge about the relation between the avoidance response and the US (R-S knowledge). As the expectancy-based theory of Lovibond (2006) is the only theory of avoidance that incorporates both knowledge structures, the results provide unique support for this theory.     

Multiple memory stores and operant conditioning: a rationale for memory's complexity

Why does the brain contain more than one memory system? Genetic algorithms can play a role in elucidating this question. Here, model animals were constructed containing a dorsal striatal layer that controlled actions, and a ventral striatal layer that controlled a dopaminergic learning signal. Both layers could gain access to three modeled memory stores, but such access was penalized as energy expenditure. Model animals were then selected on their fitness in simulated operant conditioning tasks. Results suggest that having access to multiple memory stores and their representations is important in learning to regulate dopamine release, as well as in contextual discrimination. For simple operant conditioning, as well as stimulus discrimination, hippocampal compound representations turned out to suffice, a counterintuitive result given findings that hippocampal lesions tend not to affect performance in such tasks. We argue that there is in fact evidence to support a role for compound representations and the hippocampus in even the simplest conditioning tasks.     

Stimulus characteristics that can enhance or decrease aggression: Associations with prior positive or negative reinforcements for aggression

To establish an analogue of the “weapons effect,” male university subjects were required to use a distinctive apparatus in delivering noxious sounds to a peer in an adjoining room, and then were either (a) positively reinforced, or (b) negatively reinforced, or (c) not given any reaction by the experimenter, for what they had done. Immediately after this, each person had to administer other noise blasts to someone else in a different manner, but with the previous noise machines (the fist “weapon”) being either present or not present. The initial “weapon's” presence augmented the effects of the prior reinforcement; the second victim was attacked most strongly after the men had been positively reinforced and the earlier “weapon” was nearby, whereas he received the fewest blasts if the subjects had been negatively reinforced and the earlier noise machine was present. Other evidence indicates (1) that the aggressive cue, the “weapon,” had not affected the subjects' aggressive intentions, (2) the results are not due simply to differences in moods or general arousal, and (3) the subjects were not aware of the hypothesis regarding the interaction of reinforcement and cue presence.     

Autoshaping the pigeon's gape response: acquisition and topography as a function of reinforcer type and magnitude.

The pigeon's key-pecking response is experimentally dissociable into transport (head movement) and gape (jaw movement) components. During conditioning of the key-pecking response, both components come under the control of the conditioned stimulus. To study the acquisition of gape conditioned responses and to clarify the contribution of unconditioned stimulus (reinforcer) variables to the form of the response, gape and key-contact responses were recorded during an autoshaping procedure and reinforcer properties were systematically varied. One group of 8 pigeons was food deprived and subgroups of 2 birds each were exposed to four different pellet sizes as reinforcers, each reinforcer signaled by a keylight conditioned stimulus. A second group was water deprived and received water reinforcers paired with the conditioned stimulus. Water- or food-deprived control groups received appropriate water or food reinforcers that were randomly delivered with respect to the keylight stimulus. Acquisition of the conditioned gape response frequently preceded key-contact responses, and gape conditioned responses were generally elicited at higher rates than were key contacts. The form of the conditioned gape was similar to, but not identical with, the form of the unconditioned gape. The gape component is a critical topographical feature of the conditioned key peck, a sensitive measure of conditioning during autoshaping, and an important source of the observed similarities in the form of conditioned and consummatory responses.