Academic journal article Attention, Perception and Psychophysics

How Does Attention Spread across Objects Oriented in Depth?

Academic journal article Attention, Perception and Psychophysics

How Does Attention Spread across Objects Oriented in Depth?

Article excerpt

Previous evidence suggests that attention can operate on object-based representations. It is not known whether these representations encode depth information and whether object depth, if encoded, is in viewer- or object-centered coordinates. To examine these questions, we employed a spatial cuing paradigm in which one corner of a 3-D object was exogenously cued with 75% validity. By rotating the object in depth, we can determine whether validity effects are modulated by 2-D or 3-D cue-target distance and whether validity effects depend on the position of the viewer relative to the object. When the image of a 3-D object was present (Experiments 1A and 1B), validity effects were not modulated by changes in 2-D cue-target distance, and shifting attention toward the viewer led to smaller validity effects than did shifting attention away from the viewer. When there was no object in the display (Experiments 2A and 2B), validity effects increased linearly as a function of 2-D cue-target distance. These results demonstrate that attention spreads across representations of perceived objects that encode depth information and that the object's orientation in depth is encoded in viewer-centered coordinates.

The properties of selective attention in both 2-D and 3-D space have been extensively studied using exogenous spatial cuing paradigms in which one display location is cued before an ensuing target (e.g., Downing & Pinker, 1985; Posner, 1980). In 2-D space, when the target appears within half a second or less from the cue onset, participants are more accurate and faster to respond when the target appears at the cued location (valid cue trials) than when it appears at unexpected or invalidly cued locations (invalid cue trials). In addition, the performance difference between valid and invalid cue trials, termed a validity effect, can depend on the spatial distance between the cue and the target, with longer distances leading to larger validity costs (e.g., Egly & Homa, 1991; Posner, 1980).

Studies of selective attention in 3-D space have also shown that attention can be allocated to distinct locations in depth, with costs of attention arising when attention shifts from a location in one depth plane to a location in another depth plane (e.g., Andersen, 1990; Andersen & Kramer, 1993; Arnott & Shedden, 2000; Atchley, Kramer, Andersen, & Theeuwes, 1997; Downing & Pinker, 1985; Gawryszewski, Riggio, Rizzolatti, & Umiltà, 1987; He & Nakayama, 1995; Theeuwes, Atchley, & Kramer, 1998). These studies show that depth is encoded in our representation of space and that this representation can be accessed by selective attention. Furthermore, some studies on selective attention in 3-D space have shown that shifting attention away from the viewer leads to larger validity effects than does shifting attention toward the viewer, suggesting that 3-D space is represented in viewer-centered coordinates (e.g., Andersen, 1990; Andersen & Kramer, 1993; Arnott & Shedden, 2000; Downing & Pinker, 1985; Gawryszewski et al., 1987).

In addition to evidence that selective attention operates across empty space, there is considerable evidence that the presence of objects can alter the way selective attention is allocated in both 2-D and 3-D space. Studies using objects (e.g., rectangles) extending to different locations in two dimensions have shown that whole objects can be selected (e.g., Baylis & Driver, 1992; Egly, Driver, & Rafal, 1994), as can individual object parts (e.g., Leek, Reppa, & Tipper, 2003; Reppa & Leek, 2003, 2006; Vecera, Behrmann, & Filapek, 2001; Vecera, Behrmann, & McGoldrick, 2000). Differences in validity effects between two locations that are part of an object are observed to be smaller than those between two locations on different objects, even if the spatial distance is equivalent (e.g., Egly et al., 1994). These findings show that shifts of attention from one location to another can be reduced if those locations are part of the same object (e. …

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