Abstract
The subjective boundary effect (SBE) describes a performance impairment at the boundaries of subjectively defined regions (Carrasco & Chang, 1995). We investigated whether the SBE, resulting from sustained attention, can be eliminated or reduced by transient attention. In Exp 1, observers reported whether a tilted target among vertical distracters in a 9 x 9 display appeared in the leftmost, middle, or rightmost 3 columns, the boundaries of which were maintained by sustained attention. The display was preceded by a transient cue; 50% neutral cues at fixation & 50% peripheral cues directly above the possible target location. With neutral cues, the SBE was evident. Peripheral cues improved overall performance, but the SBE remained. To investigate whether the failure to affect the SBE was robust, in Exps 2 & 3 observers performed a detection task while attending to multiple disjoint regions and ignoring the regions in between, thereby engaging sustained attention in the maintenance of boundaries (Gobell, Tseng, & Sperling, 2004). In Exp 2, a transient cue preceded the search array, 50% neutral & 50% peripheral. The neutral cue appeared at fixation, whereas the peripheral cue was a line extending the length/width of the display, drawing attention to the entire row or column in which the target might appear. The peripheral cue increased accuracy, but the SBE remained. In Exp 3, to see if a transient cue which indicated only the location of the target rather than an entire row/column would eliminate the SBE, the cue was a small bar appearing directly above the potential target location. The cue increased accuracy and eliminated the SBE. Whereas the SBE was not eliminated in Exps 1 & 2, Exp 3 demonstrated that transient attention can eliminate the SBE. Reasons for the different results in Exps 1 & 3 are discussed, and a strength-map account of the data, in which both sustained & transient attention increase the strength of elements in the display, is presented.
Supported by the National Institute of Health, grant # T32 MH19524-11, and the National Eye Institute, grant # 1 F32 EY015988-01.