Academic journal article Perception and Psychophysics

Object-Based Attention: Strength of Object Representation and Attentional Guidance

Academic journal article Perception and Psychophysics

Object-Based Attention: Strength of Object Representation and Attentional Guidance

Article excerpt

Two or more features belonging to a single object are identified more quickly and more accurately than are features belonging to different objects-a finding attributed to sensory enhancement of all features belonging to an attended or selected object. However, several recent studies have suggested that this "single-object advantage" may be a product of probabilistic and configural strategic prioritizations rather than of object-based perceptual enhancement per se, challenging the underlying mechanism that is thought to give rise to object-based attention. In the present article, we further explore constraints on the mechanisms of object-based selection by examining the contribution of the strength of object representations to the single-object advantage. We manipulated factors such as exposure duration (i.e., preview time) and salience of configuration (i.e., objects). Varying preview time changes the magnitude of the object-based effect, so that if there is ample time to establish an object representation (i.e., preview time of 1,000 msec), then both probability and configuration (i.e., objects) guide attentional selection. If, however, insufficient time is provided to establish a robust object-based representation, then only probabilities guide attentional selection. Interestingly, at a short preview time of 200 msec, when the two objects were sufficiently different from each other (i.e., different colors), both configuration and probability guided attention selection. These results suggest that object-based effects can be explained both in terms of strength of object representations (established at longer exposure durations and by pictorial cues) and probabilistic contingencies in the visual environment.

Research has established that attentional guidance during visual processing is mediated by spatial locations; target detection at a cued location in space is better than detection at other, uncued locations (Downing & Pinker, 1985; Eriksen & St. James, 1986; Posner, Snyder, & Davidson, 1980). Over the past two decades, however, considerable evidence has accumulated suggesting that attentional selection can also be mediated by objects that are present in the environment. This latter perspective gained ground after several studies demonstrated a benefit that was associated with selecting features of an attended object as compared with features of an unattended object, even when the two relevant objects were superimposed spatially (Duncan, 1984; Kahneman & Henik, 1981 ; Rock & Guttman, 1981). Research has suggested that both objects and spatial locations influence attentional selection.

A large body of evidence in support of object-based attentional selection has been derived from a paradigm that was originally developed by Egly, Driver, and Rafal (1994) and referred to as the two-rectangle method (Marrara & Moore, 2003). In this paradigm, two adjacent rectangles-oriented either vertically or horizontally-are presented to the observer. After a brief delay, one end of one of the rectangles is illuminated briefly-an event that cues the observer to direct attention to a specific location while maintaining fixation at the center of the display. After another brief delay, a target is presented in the location previously occupied by the cue (a validly cued location), in the opposite end of the cued rectangle (an invalid same-object location), or in the other rectangle (an invalid different-object location) at the same distance from the cue as the invalid same-object location. This paradigm yields two main findings: Items in the validly cued location are detected faster and more accurately than are items presented in any other location. This result reflects the fact that spatial distance between the cued location and the target affects the quality of the perceptual representation (Desimone & Duncan, 1995; Müller, Bartelt, Donner, Villringer, & Brandt, 2003; Posner et al., 1980), and it is consistent with spatial attentional-cuing findings to date. …

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