Learning to fear a second-order stimulus following vicarious learning

Vicarious fear learning refers to the acquisition of fear via observation of the fearful responses of others. The present study aims to extend current knowledge by exploring whether second-order vicarious fear learning can be demonstrated in children. That is, whether vicariously learnt fear responses for one stimulus can be elicited in a second stimulus associated with that initial stimulus. Results demonstrated that children's (5–11 years) fear responses for marsupials and caterpillars increased when they were seen with fearful faces compared to no faces. Additionally, the results indicated a second-order effect in which fear-related learning occurred for other animals seen together with the fear-paired animal, even though the animals were never observed with fearful faces themselves. Overall, the findings indicate that for children in this age group vicariously learnt fear-related responses for one stimulus can subsequently be observed for a second stimulus without it being experienced in a fear-related vicarious learning event. These findings may help to explain why some individuals do not recall involvement of a traumatic learning episode in the development of their fear of a specific stimulus.     

Counterintuitive effects of negative social feedback on attention

Which stimuli we pay attention to is strongly influenced by learning. Stimuli previously associated with reward outcomes, such as money and food, and stimuli previously associated with aversive outcomes, such as monetary loss and electric shock, automatically capture attention. Social reward (happy expressions) can bias attention towards associated stimuli, but the role of negative social feedback in biasing attentional selection remains unexplored. On the one hand, negative social feedback often serves to discourage particular behaviours. If attentional selection can be curbed much like any other behavioural preference, we might expect stimuli associated with negative social feedback to be more readily ignored. On the other hand, if negative social feedback influences attention in the same way that other aversive outcomes do, such feedback might ironically bias attention towards the stimuli it is intended to discourage selection of. In the present study, participants first completed a training phase in which colour targets were associated with negative social feedback. Then, in a subsequent test phase, these same colour stimuli served as task-irrelevant distractors during a visual search task. The results strongly support the latter interpretation in that stimuli previously associated with negative social feedback impaired search performance.     

Stress associated changes in Pavlovian-instrumental transfer in humans

Predictive learning is known to influence instrumental responding for reward. Cues associated with an instrumental outcome can influence performance in two ways: (a) by selectively promoting actions associated with the outcome predicted by the cue (specific transfer), and (b) by increasing motivation and the vigour of instrumental responding (general transfer). To examine these two distinct processes in humans we developed a novel behavioural task in which participants were able to liberate junk-food snacks from a virtual vending machine. Additionally, the relationship between stress and cue-driven reward seeking was examined using participant scores on the Depression Anxiety and Stress Scale (DASS). Reward-paired cues were found to separately bias action selection and influence the rate of responding for rewards. Furthermore, the effects of reward-paired cues on the rate of responding for reward was influenced by increased stress and anxiety. Increased levels of stress and anxiety were associated particularly with changes in cue-driven response vigour; whereas high levels of stress and anxiety were associated with elevated responding above baseline in the presence of a cue associated with a non-rewarding outcome, participants with low levels of anxiety and stress showed appropriate suppression of responding during this cue. These differences in performance between high and low anxiety and stress participants provides initial evidence that, as has been demonstrated in rodents, stress affects the influence of cue-driven response vigour in humans.     

Interoceptive awareness and unaware fear conditioning: are subliminal conditioning effects influenced by the manipulation of visceral self-perception?

Research has shown repeatedly that attention influences implicit learning effects. In a similar vein, interoceptive awareness might be involved in unaware fear conditioning: The fact that the CS is repeatedly presented in the context of aversive bodily experiences might facilitate the development of conditioned responding. We investigated the role of interoceptive attention in a subliminal conditioning paradigm. Conditioning was embedded in a spatial cueing task with subliminally presented cues that were followed by a masking stimulus. Response times to the targets that were either validly or invalidly predicted by the cues served as index of conditioning. Interoceptive attention was manipulated between-subjects. Half the participants completed a heartbeat detection task before conditioning. This task tunes attention to one’s own bodily signals. We found that conditioned responding was facilitated in this latter group of participants. These results are in line with the hypothesis that a rise interoceptive attention enhances unaware conditioned responding.     

Intertrial pellets influence the acquisition and expression of timed appetitive responding in rats

Two experiments examined temporally based changes in the conditioned magazine-entries of rats when a target food pellet arrived at a fixed time before the termination of a conditioned stimulus. Both experiments found that increasing the rate of intertrial pellets systematically interfered with the rate of acquisition. When intertrial pellets were featured in acquisition, their omission on test trials also resulted in a very poorly expressed conditioned response. On test trials preceded by intertrial pellets, however, peak times in groups trained with intertrial pellets were shifted in a rightward direction under a long but not short interstimulus interval. This rightward shift was accompanied by a smaller standard deviation. Our key findings are best accommodated by real-time associative models.     

A new tool for assessing context conditioning induced by US-unpredictability in humans: The Martians task restyled

Unpredictability of an unconditioned stimulus (US) typically produces context conditioning in animals and humans. We modified the Martians task - a computer game measuring learning of Pavlovian associations through conditioned suppression - for assessing context conditioning in humans. One between-subjects and one within-subjects study are reported. Both experiments comprised four conditions: a predictable (Paired) condition in which the conditioned stimulus (CS) signaled the US, a neutral condition (No-US), one unpredictable condition in which the CS did not signal the US (Unpaired) and another one in which only unsignaled, temporally unpredictable USs were presented (US-only). Results showed more contextual conditioned suppression in the unpredictable conditions compared to the predictable condition. In contrast, more cued conditioned suppression occurred in the Paired condition than in the Unpaired condition. Consistent with animal research, context conditioning was increased by unpredictability. These data support the Martians task as a promising tool to extend research on human context conditioning.     

Mechanisms of resurgence II: Response-contingent reinforcers can reinstate a second extinguished behavior

Three experiments with rat subjects examined resurgence of an extinguished instrumental response using the procedure introduced by Epstein (1983) with pigeons. There were three phases: (1) initial acquisition of pressing on a lever (L1) for pellet reward, (2) extinction of L1, and (3) a test session in which a second lever (L2) was inserted, briefly reinforced, and then extinguished. Experiment 1 confirmed that if pressing L2 delivered 20 pellets followed by extinction, rats would resume L1 responding in the final test. Experiment 2 compared the effects of response-contingent and non-contingent rewards delivered upon insertion of L2. Although insertion of L2 alone did not increase L1 responding, response-contingent and non-contingent rewards led to comparable increases in L1 responding. Experiment 3 found that the delivery of non-contingent pellets during extinction of L1, which would be expected to reduce the ability of pellets to set the occasion for the L1 response, also reduced the effects of both response-contingent and non-contingent rewards during the final test. The results indicate that in this method, the resurgence treatment leads to an increase in L1 pressing due to simple presentation of the pellet; delivering the reinforcer after extinction of L1 reinstates L1 responding by setting the occasion for the L1 response.     

Return of fear after retrospective inferences about the absence of an unconditioned stimulus during extinction

We examined whether the effect of an extinction phase can be influenced retrospectively by information about the cause of the absence of the unconditioned stimulus (US) during that phase. Participants were subjected to a differential fear conditioning procedure, followed by an extinction procedure. Afterwards, half of the participants were presented with information about a technical failure, which explained why the US had been absent during the extinction phase. The other participants received information that was unrelated to the US. During a subsequent presentation of the target conditioned stimulus (CS), only the former group of participants showed renewed anticipatory skin conductance responding and a return of US expectancy. The results are in accordance with a propositional account of associative learning and highlight the importance of retrospective reasoning as a cause of relapse after exposure therapy.