Fig. 2.

Examples of 100% position-symmetric stimuli used in Experiment 1 (A–C), 50% position-symmetric stimuli used in Experiment 2 (D–H), and chromatic stimuli used in Experiment 3 (I–K). A) Anti-symmetric patterns in which position-symmetric dots were of opposite luminance-polarity across the symmetry axis; B) Polarity-grouped – the same as the anti-symmetric condition but with one half of the pattern of one luminance polarity and the other of opposite polarity; C) Unsegregated – symmetric-pairs were the same luminance polarity, with an equal number of black and white dot pairs. (D–H) Examples of 50% position-symmetric patterns used in Experiment 2: (D) Anti-symmetric; (E) Polarity-grouped anti-symmetric; (F) Unsegregated; (G) Segregated in which symmetrical pairs are black and noise dots are white; (H) Single polarity patterns. In this experiment, we also used single polarity patterns with 100% position symmetry (not shown). (I–K) Examples of 100% position-symmetric chromatic stimuli made of two (I), three (J) or four (K) colours.