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Peter Squire, Pamela Greenwood, Raja Parasuraman; Are shifting, splitting, and scaling of attention similar processes?. Journal of Vision 2008;8(6):948. doi: 10.1167/8.6.948.
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Background: The focus of visual attention can be distributed in at least three different ways: (1) shifting to one location (Posner, Snyder, & Davidson, 1980), (2) splitting between non-contiguous locations (Kramer & Hahn, 1995), or (3) scaling attention over a large or small area (Eriksen & St James, 1986). While some evidence suggests that the type of distribution influences task performance (McMains & Somers, 2005), it is unknown how performance changes as a function of (a) time required for cue effectiveness (i.e. SOA) or (b) type of distribution. Based on previous research, we hypothesized that the optimal cue facilitation time is similar for shifting and splitting attention (Kramer & Hahn, 1995), but slower for scaling (Greenwood & Parasuraman, 2004). The hypothesis was tested by varying cue-target SOAs. Method: A modified Awh & Pashler (2000) paradigm was used: a location precue to a target digit in a search array of distractor letters. Conditions were: no-cue (control), one cue (shifting), two non-contiguous cues (splitting), three contiguous cues (scaling) with a range of SOAs from 50 to 200 ms. All cues were valid in predicting target location. Following the presentation of the cue(s) a target array was displayed. Following array offset, participants made unspeeded responses about the presence of the target digit. Accuracy of target response was analyzed as a function of SOA and cue type. Results and Conclusions: For all distribution conditions (except control) accuracy increased with time. In addition, splitting and shifting developed faster (and in a time course consistent with the shifting literature) than scaling. Although splitting may not occur if distractors are absent (Awh & Pashler, 2000), this finding suggests that in the presence of distractors there may be more processing overlap between splitting and shifting than between either and scaling.
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