Further Illustrations To Understand Interference by Task-Irrelevant Features

<div><p>(A–C) As in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.0030062#pcbi-0030062-g001" target="_blank">Figure 1</a>, the schematics of texture stimuli of various feature contrasts in task-relevant and -irrelevant features.</p><p>(D) Like (A), except that each bar is 10° from vertical, reducing orientation contrast to 20°.</p><p>(F) Derived from (C) by replacing each texture element of two intersecting bars by one bar whose orientation is the average of the original two intersecting bars.</p><p>(G–I) Derived from (A–C) by reducing the orientation contrast (to 20°) in the interfering bars, each is 10° from horizontal.</p><p>(J–L) Derived from (G–I) by reducing the task-relevant contrast to 20°.</p><p>(E) Plots the normalized RTs for three subjects, DY, EW, and TT, on stimuli (A,D,F,C,I,L) randomly interleaved within a session. Each normalized RT is obtained by dividing the actual RT by the RT (which are 471, 490, and 528 ms, respectively, for subjects DY, EW, and TT) of the same subject for stimulus (A).</p><p>For each subject, RT for (C) is significantly (<i>p</i> < 0.001) higher than that for (A,D,F,I) by at least 95%, 56%, 59%, and 29%, respectively. Matched sample <i>t</i>-test across subjects shows no significant difference (<i>p</i> = 0.99) between RTs for stimuli (C) and (L).</p>