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VPL-reports, 12, 1-32

Distance versus hemifield costs in the identification of cued double targets.

Hans-Christoph Nothdurft
Visual Perception Laboratory (VPL) Göttingen

The paradigm of cued visual selection was used to measure the identification speed of single targets and target pairs in large item arrays. Four target categories were tested: oblique lines (orientation, Exp.1 and 5a), vertical bars with the upper and lower halves slightly displaced (Vernier's, Exp.2), T letters at four orientations (T's, Exp.3), and red or green oblique lines (conjunctions, Exp.4 and 5). In all experiments, performance with double targets in various distances from another was compared with that for single targets at the same presentation time. Despite reported differences in the need of attention for their discrimination, all four target types revealed similar performance characteristics in the task. The identification of double targets was strongly disturbed at near target distances (2.5 deg), slightly disturbed at medium distances (6.5 deg), and not or only little disturbed at far target distances (12 deg). Also the identification of individual targets in target pairs was usually worse than that of single targets, except at far distances. In later analysis, target pairs were also distinguished whether they had been located in same or different visual hemifields. It turned out that all near target pairs were located in same, all far target pairs in different hemifields. To disentangle hemifield from distance variations, a new set of target positions was tested (Exp.5), in which near and far distances occurred both within and across hemifields. The results revealed a clear predominance of hemifield effects. The identification of target pairs presented in same hemifields was notably worse than the identification of target pairs presented in different hemifields. Distance variations had almost no effect. In an aside finding, the study collected further evidence for an independent feature processing in conjunctions; the color of colored lines was always faster identified than their orientation (Exp.4). This questions the need of attentional binding processes in the identification of certain conjunction targets.

Published online: 28-Jul-2020

Citation: Nothdurft, H.C. (2020). Distance versus hemifield costs in the identification of cued double targets. VPL-reports, 12, 1-32, www.vpl-reports.de/12/

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