From passivity to persistence : translational investigations of avoidance learning across depressive symptoms

Avoidance behaviour is a prominent feature of depression, yet the behavioural processes through which depressive symptoms influence avoidance learning and action selection remain poorly understood. Across three complementary studies, this dissertation examined how depressive symptoms—measured dimensionally in a non-clinical sample—were associated with reinforcement-based learning and action selection under aversive, mixed reward–avoidance, and ambiguous contexts. In Study 1, participants with higher depressive symptom scores showed delayed acquisition of active avoidance but intact inhibitory avoidance, suggesting difficulty initiating instrumental action under threat. Study 2 introduced a mixed-motivation paradigm interleaving reward and avoidance trials, suggesting that reward cues may alter the expression of depressive symptom–related differences observed under purely aversive conditions. Study 3 used a novel avoidance-generalization task contrasting active and inhibitory responses under ambiguity, where elevated depressive symptoms predicted greater active avoidance and persistent active-like responding, extending evidence that depressive symptom–related differences in avoidance depend on learning context and task demands. Across three complementary studies, depressive symptoms were not associated with generalized deficits in instrumental avoidance, but with context-dependent patterns of behaviour that may reflect differences in control allocation across learning phases, motivational contexts, and incentive structures, manifesting as passivity or persistence depending on situational demands.