Reinstatement after human feature-positive discrimination learning

Ambiguity drives higher-order Pavlovian learning

In the natural world, stimulus-outcome associations are often ambiguous, and most associations are highly complex and situation-dependent. Learning to disambiguate these complex associations to identify which specific outcomes will occur in which situations is critical for survival. Pavlovian occasion setters are stimuli that determine whether other stimuli will result in a specific outcome. Occasion setting is a well-established phenomenon, but very little investigation has been conducted on how occasion setters are disambiguated when they themselves are ambiguous (i.e., when they do not consistently signal whether another stimulus will be reinforced). In two preregistered studies, we investigated the role of higher-order Pavlovian occasion setting in humans. We developed and tested the first computational model predicting direct associative learning, traditional occasion setting (i.e., 1st-order occasion setting), and 2nd-order occasion setting. This model operationalizes stimulus ambiguity as a mechanism to engage in higher-order Pavlovian learning. Both behavioral and computational modeling results suggest that 2nd-order occasion setting was learned, as evidenced by lack and presence of transfer of occasion setting properties when expected and the superior fit of our 2nd-order occasion setting model compared to the 1st-order occasion setting or direct associations models. These results provide a controlled investigation into highly complex associative learning and may ultimately lead to improvements in the treatment of Pavlovian-based mental health disorders (e.g., anxiety disorders, substance use).

Pavlovian occasion setting in human fear and appetitive conditioning: Effects of trait anxiety and trait depression

Contexts and discrete stimuli often hierarchically influence the association between a stimulus and outcome. This phenomenon, called occasion setting, is central to modulation-based Pavlovian learning. We conducted two experiments with humans in fear and appetitive conditioning paradigms, training stimuli in differential conditioning, feature-positive discriminations, and feature-negative discriminations. We also investigated the effects of trait anxiety and trait depression on these forms of learning. Results from both experiments showed that participants were able to successfully learn which stimuli predicted the electric shock and monetary reward outcomes. Additionally, as hypothesized, the stimuli trained as occasion setters had little-to-no effect on simple reinforced or non-reinforced stimuli, suggesting the former were indeed occasion setters. Lastly, in fear conditioning, trait anxiety was associated with increases in fear of occasion setter/conditional stimulus compounds; in appetitive conditioning, trait depression was associated with lower expectations of monetary reward for the trained negative occasion setting compound and transfer of the negative occasion setter to the simple reinforced stimulus. These results suggest that clinically anxious individuals may have enhanced fear of occasion setting compounds, and clinically depressed individuals may expect less reward with compounds involving the negative occasion setter.

Assessing the blocking of occasion setting

An occasion setter (OS) is a stimulus or context with the capacity to disambiguate an ambiguous conditioned stimulus (CS). Previous research has shown that OSs share some features with regular Pavlovian CSs. Amongst them, research has shown that OSs are subject to blocking; that is, a new OS exerts reduced behavioral control after training in compound with a previously established OS. Of additional interest, in Pavlovian blocking, it has been reported that a blocked CS comes to elicit conditioned responding after the extinction of the blocking CS. This is an example of retrospective revaluation, a family of phenomena in which the response to a specific stimulus is modified by training a related cue. Here, three experiments sought to extend the analogies between OS and Pavlovian conditioning by examining the blocking of OSs and its retrospective revaluation. In all experiments, an OS was established by pairing a CS with food in the presence of the OS, but not in its absence (i.e., positive OS). Blocking was then trained by presenting the OS in compound with a novel OS. Experiment 1 showed blocking of the second OS, but direct exposure to the blocking OS did not enhance responding to the second OS. Experiment 2 replicated the blocking effect but subsequent training of the blocking OS with a reversed contingency showed no retrospective revaluation. Experiment 3 examined whether blocking of the OS occurred with a novel CS during the compound phase. In this experiment blocking was again observed, but only when subjects were tested with the original CS. These results are discussed focusing on the underlying links at work in occasion setting.