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Summary: Processing of one, two or four natural scenes in humans:
the limits of parallelism
Guillaume A. Rousselet *, Simon J. Thorpe, Michele Fabre-Thorpe
Centre de Recherche Cerveau et Cognition (UMR 5549, CNRS-UPS), Faculte de Medecine de Rangueil,
133 route de Narbonne, 31062 Toulouse, France
Received 6 October 2003; received in revised form 20 November 2003
Abstract
The visual processing of objects in natural scenes is fast and efficient, as indexed by behavioral and ERP data [Nature 381 (1996)
520]. The results from a recent experiment suggested that such fast routines work in parallel across the visual field when subjects
were presented with two natural scenes simultaneously [Nature Neurosci. 5 (2002) 629]. In the present experiment, the visual system
was driven to its limits by presenting one, two or four scenes simultaneously. Behavior and ERP reveal a clear cost in processing an
increasing number of scenes. However, a parallel-late selection model can still account for the results. This model is developed and
discussed with reference to behavioral, single-unit and ERP data.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Natural scenes; Rapid categorization; Attention; Event-related potentials (ERP); Human performance
1. Introduction
Our ability to face complex and unpredictable
environments seems to rely on several mechanisms
involving fast and parallel visual routines. The very
rapid categorization of briefly presented pictures (Bie-
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