Zusammenfassung
Hard-wired, Pavlovian, responses elicited by predictions of rewards and punishments exert significant benevolent and malevolent influences over instrumentally-appropriate actions. These influences come in two main groups, defined along anatomical, pharmacological, behavioural and functional lines. Investigations of the influences have so far concentrated on the groups as a whole; here we take the critical step of looking inside each group, using a detailed reinforcement learning model to distinguish effects to do with value, specific actions, and general activation or inhibition. We show a high degree of sophistication in Pavlovian influences, with appetitive Pavlovian stimuli specifically promoting approach and inhibiting withdrawal, and aversive Pavlovian stimuli promoting withdrawal and inhibiting approach. These influences account for differences in the instrumental performance of approach and withdrawal behaviours. Finally, although losses are as informative as gains, we find that subjects neglect losses in their instrumental learning. Our findings argue for a view of the Pavlovian system as a constraint or prior, facilitating learning by alleviating computational costs that come with increased flexibility. Beautiful background music in a shop may well tempt us to buy something we neither need nor want. Valenced stimuli have broad and profound influences on ongoing choice behaviour. After replicating known findings whereby approach is enhanced by appetitive Pavlovian stimuli and inhibited by aversive ones, we extend this to withdrawal behaviours, but critically controlling for the valence of the withdrawal behaviours themselves. We find that even when withdrawal is appetitively motivated, it is still inhibited by appetitive Pavlovian stimuli and enhanced by aversive ones. This shows, for the first time, that the effect of background Pavlovian stimuli depends critically on the intrinsic valence of behaviours, and differs between approach and withdrawal.
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