The temporal lobe has cells relevant to selective attention. If that rectangle is a signal for rewards, likely it will be attended-to, and the cell will repond more strongly. This suggests some inhibition becomes involved. Divided attention is reletively inefficient. Binocular rivalry results if two very different signals are presented to the two eyes.
Dichotic listeners fail to pick up target words is deviding attention.
Typists can sight-type and shadow very well. Saccades are influenced by the structure of the scene, and by our purpose. Novel objects found in search of scenes hold our fixation longer. The kinds of features for which we search, and their relations, affect our efficiency. Neisser noted we could search through distractors to find target letters at 60 letters per sec.