Four Common Conceptual Fallacies in Mapping the Time Course of Recognition

Rufin Vanrullen

doi:10.3389/fpsyg.2011.00365

Abstract

Determining the moment at which a visual recognition process is completed, or the order in which various processes come into play, are fundamental steps in any attempt to understand human recognition abilities, or to replicate the corresponding hierarchy of neuronal mechanisms within artificial systems. Common experimental paradigms for addressing these questions involve the measurement and/or comparison of backward-masking (or rapid serial visual presentation) psychometric functions and of physiological EEG/MEG/LFP signals (peak latencies, differential activities, single-trial decoding techniques). I review and illustrate four common mistakes that scientists tend to make when using these paradigms, and explain the conceptual fallacies that motivate their reasoning. First, contrary to collective intuition, presentation times, or stimulus-onset asynchrony masking thresholds cannot be taken to reflect, directly or indirectly, the timing of relevant brain processes. Second, psychophysical or electrophysiological measurements should not be compared without assessing potential physical differences between experimental stimulus sets. Third, such comparisons should not be performed in any manner contingent on subjective responses, so as to avoid response biases. Last, the filtering of electrophysiological signals alters their temporal structure, and thus precludes their interpretation in terms of time course. Practical solutions are proposed to overcome these common mistakes.

Highlights

A major portion of vision science is devoted to investigating the timing of perceptual processes: the absolute latency or the relative order in which they arise after a novel object enters the visual scene or after we open our eyes onto a novel scene
Example questions include: how long does it take the visual system to detect, recognize, categorize, or identify an object? how long to get the gist of the scene, and how long for a detailed analysis? do detection and categorization processes happen sequentially, or all at the same time? how about different levels of categorization? For each of these questions, there exist many experimental approaches relying on psychophysical measurements and sometimes accompanied by recordings of electrophysiological activity
While nothing can be done about the first reason, the present manuscript is an attempt at correcting the second reason

Summary

Four common conceptual fallacies in mapping the time course of recognition

Reviewed by: Ryota Kanai, University College London, UK Gabriel Kreiman, Harvard Medical School, USA. Common experimental paradigms for addressing these questions involve the measurement and/or comparison of backward-masking (or rapid serial visual presentation) psychometric functions and of physiological EEG/MEG/LFP signals (peak latencies, differential activities, single-trial decoding techniques). I review and illustrate four common mistakes that scientists tend to make when using these paradigms, and explain the conceptual fallacies that motivate their reasoning. Psychophysical or electrophysiological measurements should not be compared without assessing potential physical differences between experimental stimulus sets. Such comparisons should not be performed in any manner contingent on subjective responses, so as to avoid response biases. Practical solutions are proposed to overcome these common mistakes

INTRODUCTION

Findings

CONCLUSION