Abstract
Positive and negative moods can be treated as prior expectations over future delivery of rewards and punishments. This provides an inferential foundation for the cognitive (judgement) bias task, now widely-used for assessing affective states in non-human animals. In the task, information about affect is extracted from the optimistic or pessimistic manner in which participants resolve ambiguities in sensory input. Here, we report a novel variant of the task aimed at dissecting the effects of affect manipulations on perceptual and value computations for decision-making under ambiguity in humans. Participants were instructed to judge which way a Gabor patch (250ms presentation) was leaning. If the stimulus leant one way (e.g. left), pressing the REWard key yielded a monetary WIN whilst pressing the SAFE key failed to acquire the WIN. If it leant the other way (e.g. right), pressing the SAFE key avoided a LOSS whilst pressing the REWard key incurred the LOSS. The size (0–100 UK pence) of the offered WIN and threatened LOSS, and the ambiguity of the stimulus (vertical being completely ambiguous) were varied on a trial-by-trial basis, allowing us to investigate how decisions were affected by differing combinations of these factors. Half the subjects performed the task in a ‘Pleasantly’ decorated room and were given a gift (bag of sweets) prior to starting, whilst the other half were in a bare ‘Unpleasant’ room and were not given anything. Although these treatments had little effect on self-reported mood, they did lead to differences in decision-making. All subjects were risk averse under ambiguity, consistent with the notion of loss aversion. Analysis using a Bayesian decision model indicated that Unpleasant Room subjects were (‘pessimistically’) biased towards choosing the SAFE key under ambiguity, but also weighed WINS more heavily than LOSSes compared to Pleasant Room subjects. These apparently contradictory findings may be explained by the influence of affect on different processes underlying decision-making, and the task presented here offers opportunities for further dissecting such processes.
Highlights
It is well established that emotional states influence the way that we process sensory stimuli, and thereby the decisions we make based on those stimuli
By exposing subjects to one of two affect manipulation conditions intended to generate either a positive or negative affective state, we investigate whether model parameter values differ between the two conditions
We added trial-by-trial variations in the offered rewards and threatened punishments to the conventional variations in perceptual ambiguity, allowing us to probe how decisions were affected by these different factors and their interactions, and how this was influenced by manipulations of affective state
Summary
It is well established that emotional states influence the way that we process sensory stimuli, and thereby the decisions we make based on those stimuli. There are exceptions and specificities [5], negatively and positively valenced affective states seem to be associated respectively with negatively and positively biased information processing. These links between affect and decision-making inspired us to develop a non-linguistic task that used cognition and choice as an indicator of affective state in humans and other animals [6]. Negative mood would favour cautious or pessimistic decisions under ambiguity [9], and so could be determined from a bias towards N This could be validated, for instance, by examining the consequence in the task of the regular experience of negative events. In Harding et al.’s study [7], repeated experience of mildly aversive unpredictable events resulted in a pessimistic bias as predicted
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