Spatial probability AIDS visual stimulus discrimination.
Bottom Line:
Recent results have suggested that spatial probability can be a cue for the allocation of attention in visual search.This produced fewer spatial repeats and allowed us to dissociate the effect of a high-probability location from that of short-term spatial repetition.These two experiments suggest that inhomogeneities in spatial probability can be learned and used by participants on-line and without prompting as an aid for visual stimulus discrimination and that spatial repetition priming is not a sufficient explanation for this effect.
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PubMed Central - PubMed
Affiliation: Department of Psychology, University of Waterloo Waterloo, ON, Canada.
ABSTRACT
We investigated whether the statistical predictability of a target's location would influence how quickly and accurately it was classified. Recent results have suggested that spatial probability can be a cue for the allocation of attention in visual search. One explanation for probability cuing is spatial repetition priming. In our two experiments we used probability distributions that were continuous across the display rather than relying on a few arbitrary screen locations. This produced fewer spatial repeats and allowed us to dissociate the effect of a high-probability location from that of short-term spatial repetition. The task required participants to quickly judge the color of a single dot presented on a computer screen. In Experiment 1, targets were more probable in an off-center hotspot of high-probability that gradually declined to a background rate. Targets garnered faster responses if they were near earlier target locations (priming) and if they were near the high-probability hotspot (probability cuing). In Experiment 2, target locations were chosen on three concentric circles around fixation. One circle contained 80% of targets. The value of this ring distribution is that it allowed for a spatially restricted high-probability zone in which sequentially repeated trials were not likely to be physically close. Participant performance was sensitive to the high-probability circle in addition to the expected effects of eccentricity and the distance to recent targets. These two experiments suggest that inhomogeneities in spatial probability can be learned and used by participants on-line and without prompting as an aid for visual stimulus discrimination and that spatial repetition priming is not a sufficient explanation for this effect. Future models of attention should consider explicitly incorporating the probabilities of targets locations and features. No MeSH data available. Related in: MedlinePlus |
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Mentions: Prior to directly addressing the effects of target location and the high-probability hotspot we first report an analysis similar to that of Geng and Behrmann (2002) and Walthew and Gilchrist (2006) where we examine the effects of targets appearing on the high-probability half of the screen. Since participants were heterogeneous in their RTs [one-way ANOVA F(11, 18714) = 379.02, p < 0.001], we used a linear mixed effects (LME) model with participants as a random effect (Baayen, 2008) and whether the target fell on the high-probability side as a categorical fixed effect. Limiting the comparison to correct trials only (pruned to eliminate anticipations and lapses by requiring RTs >150 ms and <1000 ms) showed that being on the high-probability side reduced the RTs by 16 ms [p = 0.001, 95% confidence interval (CI) 12–19 ms]. The high-probability benefit was not driven by a minority of participants, and Figure 3 shows that while RT and accuracy effects were variable in magnitude, they were consistent in direction for most participants. All participants but two showed a decrease in RT for the targets on the high-probability side and in general they also increased in accuracy. Thus, targets on the high-probability side were responded to more quickly and with no decrease in accuracy. Figure 4 shows that most participants individually showed linear RT increases with increasing distance to the high-probability hotspot. Is the benefit of high-probability location due simply to positional priming effects? Before considering this directly we first demonstrate that our methods and data are sufficiently sensitive to demonstrate priming effects. |
View Article: PubMed Central - PubMed
Affiliation: Department of Psychology, University of Waterloo Waterloo, ON, Canada.
No MeSH data available.