To increase efficiency, sensory systems process only a subset of available inputs in accord with the behavioural goals of the observer. The mechanisms that support the prioritization of relevant over irrelevant stimuli, referred to collectively as selective attention, can operate on the basis of spatial location, low-level visual features, or holistic objects. This chapter reviews human behavioural, electrophysiological, and neuroimaging data pertaining to the effects and control of the latter two mechanisms. Based on an increasingly rich literature spanning several decades, (...) the authors argue that even though feature- and object-based attention are often treated as independent mechanisms, they should instead be described along a single continuum in which the information selected for prioritized processing is flexibly dictated by task demands. (shrink)

In this paper we argue that awareness comes in degrees, and we propose a novel multi-factor account that spans both subjective experiences and perceptual representations. At the subjective level, we argue that conscious experiences can be degraded by being fragmented, less salient, too generic, or flash-like. At the representational level, we identify corresponding features of perceptual representations—their availability for working memory, intensity, precision, and stability—and argue that the mechanisms that affect these features are what ultimately modulate the degree of awareness. (...) We conclude the paper by demonstrating why the original interpretations of certain empirical findings that apparently pose problems for our account are, in fact, flawed. (shrink)

This review focuses on how covert attention modulates perception. It explains why attention is considered a selective process, the constructs of covert attention, and spatial endogenous and exogenous attention. This review includes the effects of spatial attention on discriminability and appearance in tasks mediated by contrast sensitivity and spatial resolution.