B.3.6.1. Introduction

Visual selective attention can be oriented rather exogenously, on the basis of the saliences in the display (Jonides, 1981; Yantis & Jonides, 1984), or endogenously, on the basis of one's incentive (Posner, 1980). This way of orienting is not restricted to the spatial dimension, but could also concern featural dimensions (e.g. orientation, colour, etc.: Von Wright, 1968). The interactions between endogenous and exogenous modes of attentional orienting represent an important topic, which was recently highly debated (Klein & Shore, 2001; Ruz & Lupiàñez, 2002; Theeuwes, 2010a, 2010b and commentaries, e.g.: Ansorge, Horstmann, & Scharlau, 2010). A large part of the current models is centred on the notion of salience map proposed by Koch and Ullman (1985; e.g. Itti & Koch, 2001; Michael et al., 2006; Wolfe, 1994). This salience map is thought to represent the saliences of the visual field independently of the underlying features. On the other hand, as an alternative, some authors rejected the idea of a salience map. Most notably, Desimone and Duncan (1995) proposed the biased competition hypothesis, further developed by Duncan and colleagues as the integrated competition hypothesis (Duncan, Humphreys, & Ward, 1997; Duncan, 2006). According to these propositions, the various items in the visual field compete for representation throughout the visual system. Selective attention then corresponds to the progressive resolving of this competition. Duncan et al. (1997) postulated that this competition occurred in various cognitive systems and tended to spread from one system to an other, so that an item that would come to get the upper hand in one system would be favoured in the other systems. Crucially, they claimed that this competition could be biased endogenously, from working memory, and exogenously, on the basis of contextual influences (conspicuousness).

The present work aimed at supporting the biased competition hypothesis, by showing that endogenous and exogenous non spatial signals could influence the competition at the same perceptual locus (provided they concerned the same perceptual dimension).