Invisible stimuli, implicit thresholds: Why invisibility judgments cannot be interpreted in isolation

TL;DR

This paper critiques the common practice of interpreting 'not-seen' judgments in unconscious cognition studies, highlighting the need for systematic manipulation of stimulus visibility to accurately assess awareness and processing.

Contribution

It challenges assumptions behind using subjective 'not-seen' judgments as indicators of unconscious perception and advocates for parametric approaches to study awareness.

Findings

Response bias affects 'not-seen' judgments.

Systematic manipulation of visibility clarifies awareness-priming relationships.

Current practices may misinterpret unconscious processing evidence.

Abstract

Some studies of unconscious cognition rely on judgments of participants stating that they have "not seen" the critical stimulus (e.g., in a masked-priming experiment). Trials in which participants gave "not-seen" judgments are then treated as those where the critical stimulus was "subliminal" or "unconscious", as opposed to trials with higher visibility ratings. Sometimes, only these trials are further analyzed, for instance, for unconscious priming effects. Here I argue that this practice requires implicit assumptions about subjective measures of awareness incompatible with basic models of categorization under uncertainty (e.g., modern signal-detection and threshold theories). Most importantly, it ignores the potential effects of response bias. Instead of taking "not-seen" judgments literally, they would better be employed in parametric experiments where stimulus visibility is manipulated systematically, not accidentally. This would allow studying qualitative and double dissociations between measures of awareness and of stimulus processing per se.