Academic journal article Attention, Perception and Psychophysics

Attentional Prioritizations Based on Spatial Probabilities Can Be Maintained on Multiple Moving Objects

Academic journal article Attention, Perception and Psychophysics

Attentional Prioritizations Based on Spatial Probabilities Can Be Maintained on Multiple Moving Objects

Article excerpt

Previous studies have shown that attention prioritizes locations that frequently contain a target. The present study examines whether these spatial prioritizations can be maintained on multiple independently moving objects. Observers viewed two line objects undergoing translational and rotational motion and detected probes appearing on the objects. The probabilities of probes appearing on the centers and ends of objects were manipulated. Experiment 1 showed that attention within moving objects is affected by location probabilities and is also heavily biased toward objects' centers. Experiment 2 showed that if the observer is not informed about location probabilities, the probabilities can be learned. Experiment 3 showed that with multiple-region objects, the center bias is reduced, but the effect of probabilities is unchanged. Experiment 4 showed that two distinct patterns of spatial prioritizations can be maintained on two objects simultaneously. These results suggest that attentional prioritizations based on spatial probabilities can occur in an object-based reference frame.

Much research has demonstrated that attending to a spatial location facilitates perceptual processing of a stimulus at that location (e.g., Posner, Snyder, & Davidson, 1980; Prinzmetal, McCool, & Park, 2005). For this reason, attention has been compared to a spotlight, enhancing processing of stimuli within an area of the visual field (e.g., Posner et al., 1980). Many studies have shown that the visual system attentionally prioritizes locations on the basis of the likelihood of a target's appearing at those locations. Targets in high-probability locations are detected more efficiently than targets in low-probability locations, which suggests that the visual system strategically allocates its resources to the locations most likely to contain a target (e.g., Geng & Behrmann, 2002, 2005; Kinchla, 1977; Shaw & Shaw, 1977).

However, many other studies have suggested that the attentional mechanism selects perceptual objects (e.g., Baylis & Driver, 1993; Duncan, 1984; Egly, Driver, & Rafal, 1994; Vecera & Farah, 1994; for a review, see Scholl, 2001). According to this object-based attentional view, attention is not directed simply to spatial locations in the visual field but to regions that have previously been segmented into objects by the perceptual organization system. A number of studies have shown that space-based and object-based attention can be present concurrently in the same task (e.g., Egly et al., 1994; Shomstein & Yantis, 2004; Soto & Blanco, 2004).

Although there is now much evidence that attention can select high-probability locations and that attention can select relevant objects, the interaction between these two mechanisms is less understood. One important question is whether attentional prioritizations based on probabilities can occur in an object-based frame of reference. That is, can attentional prioritizations be encoded relative to positions within individual objects? Relevant to this question, the effects of location probabilities within grouped configurations have been examined in a few studies. Miller (1988) presented observers with a configuration of horizontally aligned letters in which a target letter could occur with high or low probability in each of four locations. After practice, the configuration was shifted in its spatial location to the left or right so that the high- and low-probability locations were at new screen locations. Target detection was facilitated at the high-probability spatial location and at the high-probability relative position within the configuration. This suggests that probabilities facilitate relative positions within configurations, as well as absolute locations in visual space. Hoffmann and Kunde (1999) presented observers with two differently shaped configurations, each with a distinct pattern of target expectancies. They found that the observers adapted different target expectations to the locations in the two configurations. …

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