期刊
VISION RESEARCH
卷 40, 期 10-12, 页码 1293-1300出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0042-6989(00)00029-8
关键词
orientation discrimination; attention; visual noise; visual search
We have measured orientation discrimination in the presence of a variable number of neutral distracters for two distinct tasks: identification of the orientation of a tilted target and location of its position. Both tasks were performed in the presence of visual noise of variable contrasts. Under a range of conditions, subjects could identify the direction of target tilt at thresholds well below those necessary to locate its position. The location thresholds showed only weak dependency on set-size, consistent with a stimulus uncertainty of parallel search of the output of independent orientation analysers, while the identification thresholds showed a much stronger dependency, varying with the square root of set-size over a wide range noise contrasts. The square root relationship suggests perceptual summation of target and distracters. Manipulating the spread of visual noise suggests that the summation is feature-based, possibly operating on the outputs of first-stage orientation analysers. Pre-cueing the target eliminates the effects of set-size, showing that the summation is under rapid attentional control; the visual system can choose between high performance over a limited area and poorer performance over a much larger area. (C) 2000 Elsevier Science Ltd. All rights reserved.
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