The implied motion aftereffect changes decisions, but not confidence

Regan M Gallagher,Thomas Suddendorf,Derek H Arnold

doi:10.3758/s13414-021-02331-z

Regan M Gallagher, Thomas Suddendorf + Show 1 more

Open Access

https://doi.org/10.3758/s13414-021-02331-z

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Abstract

Viewing static images depicting movement can result in a motion aftereffect: people tend to categorise direction signals as moving in the opposite direction relative to the implied motion in still photographs. This finding could indicate that inferred motion direction can penetrate sensory processing and change perception. Equally possible, however, is that inferred motion changes decision processes, but not perception. Here we test these two possibilities. Since both categorical decisions and subjective confidence are informed by sensory information, confidence can be informative about whether an aftereffect probably results from changes to perceptual or decision processes. We therefore used subjective confidence as an additional measure of the implied motion aftereffect. In Experiment 1 (implied motion), we find support for decision-level changes only, with no change in subjective confidence. In Experiment 2 (real motion), we find equal changes to decisions and confidence. Our results suggest the implied motion aftereffect produces a bias in decision-making, but leaves perceptual processing unchanged.

Highlights

An outstanding question in perception research is whether our thoughts, desires, emotions, or cognitions can change how our sensory systems operate
The peak of uncertainty functions is the point of lowest confidence, which should be centred around 0% coherence for an unbiased observer
Our results suggest that the implied motion aftereffect is the result of changes to post-perceptual decision processes

Summary

Introduction

An outstanding question in perception research is whether our thoughts, desires, emotions, or cognitions can change how our sensory systems operate. Confidence can, be dissociated from categorical decision making when a cognitive bias causes a change in responding (see Gallagher et al, 2019). We reason that this can happen when people make systematically biased category judgments about stimuli that elicit uncertainty. We find evidence that viewing still photographs depicting movement changes categorisations of ambiguous inputs, but does not change confidence On this basis, we argue that it is improbable that the implied motion aftereffect has a perceptual origin

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