Context effectson probability estimation.

Wei-Hsiang Lin,Justin L Gardner,Shih-Wei Wu,Matthew F S Rushworth

doi:10.1371/journal.pbio.3000634

Abstract

Many decisions rely on how we evaluate potential outcomes and estimate their corresponding probabilities of occurrence. Outcome evaluation is subjective because it requires consulting internal preferences and is sensitive to context. In contrast, probability estimation requires extracting statistics from the environment and therefore imposes unique challenges to the decision maker. Here, we show that probability estimation, like outcome evaluation, is subject to context effects that bias probability estimates away from other events present in the same context. However, unlike valuation, these context effects appeared to be scaled by estimated uncertainty, which is largest at intermediate probabilities. Blood-oxygen-level-dependent (BOLD) imaging showed that patterns of multivoxel activity in the dorsal anterior cingulate cortex (dACC), ventromedial prefrontal cortex (VMPFC), and intraparietal sulcus (IPS) predicted individual differences in context effects on probability estimates. These results establish VMPFC as the neurocomputational substrate shared between valuation and probability estimation and highlight the additional involvement of dACC and IPS that can be uniquely attributed to probability estimation. Because probability estimation is a required component of computational accounts from sensory inference to higher cognition, the context effects found here may affect a wide array of cognitive computations.

Highlights

When we evaluate a potential reward, such as a job offer, other offers on the table form a unique context that shapes our expectations and influences the way we feel about it
Context was defined by the two stimuli the subjects encountered in a block of trials and was manipulated such that stimuli carrying the same probability of reward were experienced in two different contexts that differed in the probability of reward associated with the other stimulus present in the context (Fig 1B)
We tested Δ against 0, where D 1⁄4 b^frequency of S (fS) À ð1 À b^foverall Þ and found that Δ was not significantly different from 0 in all three reward probabilities (p > 0.05, nonparametric bootstrap test). These results provide support to the Uncertainty- and Reference-Dependent (URD) model and highlight that context effects on probability estimates are driven by the interaction of reference-dependent computation and estimated uncertainty associated with potential outcomes

Summary

Introduction

When we evaluate a potential reward, such as a job offer, other offers on the table form a unique context that shapes our expectations and influences the way we feel about it. Psychologists and economists model such expectation as a reference point and potential rewards (e.g., different job offers) as gains or losses relative to the reference point [1,2]. Such effects of contexts on valuation impact many decisions we make and are observed in humans and in many other species such as rats [3,4], birds [5], and nonhuman primates [6,7,8]. Understanding how people use probability information has received considerable attention, and people are known to subjectively weight probability information rather than using

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Conclusion