Perceptual asymmetry in vernier offset discrimination : a similar trend between the cardinal and oblique orientations

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Our previous study has demonstrated that in the cardinal orientation, offset detection depends on the relative position of the vernier bars, i.e., how the left and right or upper and lower vernier bars are displaced from each other in space (Karim & Kojima, 2008, 2010). The present study examined whether the fact can be generalized to the oblique orientation. Experiment 1 demonstrated that for a pair of vernier bars, one displaced from the other and arranged side-by-side with a large gap between them at +45° orientation observers were, on average, somewhat better at discriminating an offset if the relative position of the lower right-hand bar was to the right of the upper left-hand bar than vice versa. A similar asymmetry was evident in Experiment 2, where observers judged vernier offset for a pair of bars at -45° orientation. In that case, average acuity was significantly better when the relative position of the upper right-hand bar was to the right of the lower left-hand bar than the opposite. The asymmetries in performance were consistent across the two orientations and did not diminish with learning, thus indicating configuration-specific processing of the vernier stimuli.



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