Processing affective images in the absence of visual awareness

Abstract

Given capacity limits, the visual system must prioritize the processing of sensory inputs that are most critical to successful interactions with the environment. Neurocognitive theories suggest that humans have evolved mechanisms that operate without awareness that selectively prioritize threatening stimuli in subsequent allocation of processing resources and access to awareness. Evidence for this ‘standard hypothesis’comes from paradigms that dissociate visual input from awareness. This thesis combines a narrative review, a meta-analytic review and three empirical studies to examine the extent to which emotionally salient stimuli are prioritized in the absence of awareness.

A general introduction and review of the literature is provided in Chapter 1. The meta analysis of previous literature (Chapter 2) reveals that evidence for an unconscious processing bias for threat isundermined by insufficiently rigorous awareness measures and inadequate control of low-level confounds. Chapter 3 reveals that autonomic arousal and attentional orienting to visual threats are eliminated under conditions where observers are objectively unaware of stimuli. Chapter 4 reveals that prioritized processing of fearful faces is parsimoniously explained by effective contrast: the relationship betweentheir Fourier spectrum and the contrast sensitivity function. Importantly, this explanation does not require or involve unconscious processing mechanisms that are sensitive to threat. Chapter 5 reveals that prioritized processing of emotional face stimuli is restricted to conditions of awareness, and may be parsimoniously explained by simple low-level variability between emotional and neutral face stimuli.

Previous and present findings and analyses are considered together in the discussion (Chapter 6). It is concluded that evidence for emotion-sensitive visual processing that operates without awareness is weak and that uncritical acceptance of the standard hypothesis is premature.

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Identifiers

ORCID for Wendy Adams: orcid.org/0000-0002-5832-1056

ORCID for Matthew Garner: orcid.org/0000-0001-9481-2226

ORCID for Erich Graf: orcid.org/0000-0002-3162-4233

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