Attention: Covert

Spatial Covert Attention

Attention can be allocated by moving one's eyes toward a location, overt attention, or by attending to an area in the periphery without actually directing one's gaze toward it. This peripheral deployment of attention, known as covert attention, aids us in monitoring the environment and can inform subsequent eye movements. Cognitive, psychophysical, electrophysiological, and neuroimaging studies provide evidence for the existence of overt and covert attention in both humans (including infants) and nonhuman primates. Many of these studies have likened attention to increasing visual salience. Whereas covert attention can be deployed to more than one location simultaneously (“in parallel”), eye movements are necessarily sequential (“serial”); they can only be at one location at a given time. Many studies have investigated the interaction of overt and covert attention and the order in which they are deployed. The consensus is that covert attention precedes eye movements and their effects on perception, which in many cases are similar but in others they are not.

Hermann von Helmholtz is considered to be the first scientist to provide an experimental demonstration of covert attention (circa 1860). He experimented with a wooden box whose interior was completely dark. Looking into the box through two pinholes, he reported that he could concentrate on any part of the visual field so that when a spark came, he could focus attention independently of the position and accommodation of his eyes, and get an impression of objects in only the particular attended region. The similarities and differences between eye movements and deployment of spatial attention have been a focus for research ever since.

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