What Is Attended In Spatial Attention?

Mole's (2008 [this issue]) argument that consciousness is a necessary concomitant of attention rests on the question of what is being attended in spatial attention. His answer is space. Some authors, including ourselves, claim that the fact that the processing of unseen objects can be modulated by spatial attention (e.g. Kentridge et al., 1999; 2004; 2008; Marzouki et al., 2007; Sumner et al., 2006) demonstrates that visual attention is not a sufficient precondition for visual awareness. Mole, however, contends that as space, rather than any object that might occupy that space, is what is being attended, these experiments do not constitute evidence for a dissociation between attention and consciousness. We disagree. To understand the source of this disagreement we need to understand the various processes encompassed by the term 'attention' and to consider experimental evidence illustrating how these processes operate. We review evidence that spatial attention can be deployed with the specific goal of determining the properties of objects occupying the attended region of space. One might, for example, attend to a location with the goal of determining the colour of objects occupying that space as efficiently as possible. Mole's assumption that all that is attended in spatial attention is space is not consistent with this evidence. We conclude that attention can be directed at objects by mechanisms of so- called 'spatial attention' without those objects necessarily eliciting conscious visual experience and hence that attention is not a sufficient precondition for visual awareness.