Abstract

Whether active and passive, top-down and bottom-up, or endogenous and exogenous, attention is typically divided into two types. To show the relationship between attention and other functions (sleep, memory, learning), one needs to show whether the type of attention in question is of the active or passive variety. However, the division between active and passive is not sharp in any area of consciousness research. In phenomenology, the experience of voluntariness is taken to indicate activity, but this experience is often confused with others. In psychology, task-dependent behavior is taken to indicate activity, but is often conflated with complex automatic behavior. In neuroscience, top-down processes are taken to exclusively indicate activity despite the fact that both top-down and bottom-up activations are always present in the brain. Moreover, work in attention has shown that the results of so-called passive and active processes are sometimes inseparable. Carrasco, et al. (2004), for example, show that active attention results in the same change in perceptual contrast that is enacted by bottom-up mechanisms. Likewise, Reynolds and Desimone (2003) show that top-down and bottom-up attention effect neural contrast in the same way. Thus, the passive-active distinction does not seem to neatly separate two types of attention. Perhaps a more convincing model of attention combines active and passive processing into a single mechanism of control. One such potential model is what we call the Unitary Saliency Map Model, first suggested by Koch and Ullman (1985) and developed by Treue (2003). In such a model, top-down and bottom-up processes each feed into the same saliency map, from which attention is controlled. We argue that this makes sense of the phenomenological, psychological, and neuroscientific data. Finally, the acceptance of such a model will force us to review some of our previous findings on attention and its relation to consciousness.