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

Abstract

Contexts and discrete stimuli often 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.

Ambiguity drives higher-order Pavlovian learning

“…Due to the relative complexity of learning occasion setting vs direct associations, perhaps individuals experience greater uncertainty during occasion setting training or experience the uncertainty for more trials due to the complexity and ambiguity of occasion setting. This may lead anxious individuals to have greater fear of occasion setting combinations or depressed individuals to expect less reward from occasion setting compounds [ 8 ]. Second, our model claims that 1 st -order occasion setters can be ambiguous (as has been shown elsewhere; e.g., [ 9 , 21 ]), and it argues that CS responding will be minimal if the CS has direct inhibition, is presented with a 1 st -order negative occasion setter, and is absent of 1 st -order positive occasion setters.…”

“…Because 2 nd -order occasion setting has not been investigated in a design like this, we did not have a strong basis for a power analysis. However, we pre-registered collecting 50–75 participants per experiment based on the strong effect size of 1 st -order occasion setting as measured by US expectancy from transfer tests in our previous study (N = 80, d = .580 to 1.132; [ 8 ]). In the present experiments, we conducted post-hoc analyses of power for our most critical transfer tests (e.g., AJK2 vs AJK1, stimuli from t-tests comparing difference scores; see Tables A and B in S5 Text ).…”

“…This curtain/muted modification was done so that no learning and no reinforcement/non-reinforcement would occur during Transfer Test, allowing us to test the underlying learning processes that occurred during training with many Transfer Test trial types (see S1 Text ). We used the unambiguous CS+ and CS- as transfer test targets in many of our transfer tests based on previous experiments that exclusively used these stimuli as transfer test targets [ 8 , 25 , 26 ]. We additionally used the (un)ambiguous 1 st -order occasion setter/CS combination as transfer test targets in our remaining transfer tests.…”

“…According to the ambiguity hypothesis, a CS that always predicts the US has no ambiguity and therefore needs no other stimuli (i.e., occasion setters) to resolve which outcome it will predict on a given trial. In support, the evidence suggests that occasion setters can affect (i.e., transfer to) CSs that have undergone occasion setting training but have little-to-no effect on unambiguous CSs (e.g., CS+, CS-) (i.e., occasion setters generally do not affect responding to unambiguous CSs) [ 8 , 9 , 11 , 13 , 22 , 104 – 109 ]. CSs with partial US reinforcement but not trained with an obvious occasion setter are also ambiguous, but transfer of occasion setting to these CSs tends to not occur [ 13 , 29 ], presumably because the CS was not trained with an identifiable occasion setter.…”

“…Independence of direct associations and occasion setting has been repeatedly demonstrated across occasion setting studies [ 1 , 2 , 8 ]. Thus, in our model, direct excitation, direct inhibition, 1 st order positive occasion setting, 1 st -order negative occasion setting, 2 nd -order positive occasion setting, and 2 nd -order negative occasion setting are (largely) independent from each other–meaning, a given stimulus can simultaneously have any value of V, , P, N, P2, and N2.…”