A Continuous Measure of Object-Based Attention Sheds New Light on Its Underlying Mechanisms

Attention is largely guided by objects; when attending a location on an object, observers react faster to targets in other locations within the object than outside the object. While crucial to our understanding of attention, there is no consensus on the mechanisms underlying such object-based attention. We describe a continuous measure of object-based attention that relies on attentional modulations of the pupillary light response (PLR). This response-free measurement provided unequivocal support for one of the debated accounts – ‘attentional shifting’, which underscores the higher cost of shifting attention between objects than within an object. In each trial, a precue appeared inside or outside a black/white object. The target followed in the same location or in a different location. In two experiments (N=44), changes in the PLR matched the shifting account’s predictions, revealing slower attentional shifts when a disengagement was required (cue inside, target outside) than not required (cue outside, target inside).