Abstract
We have been trying to identify the spatial features that determine detection of curvature by using adaptation to three features used by Gheorghiu & Kingdom (2007) to study supra-threshold curvature perception. The features were shape-frequency (cycle number of periodic curvature), shape-amplitude and local curvature. The effect of adaptation was found only after adaptations to shape-amplitude (Morita & Sato, ECVP2016). The threshold found with respect to the shape amplitude was 15'' at 1 deg off from the foveal center, and was comparable to vernier acuity with similar viewing condition. This suggests that curvature detection and vernier acuity tasks were mediated, at least partially by the same mechanism. In this study, we measured and compared detection thresholds for wavy and square-wave line stimuli, both presented at 1 deg away from central fixation point. In the experiments, either wavy- or square-wave vertical line was presented either on the right or left hand side of the fixation, and was paired with straight line presented on the other side. The observer's task was to report which of the paired lines was straight (2AFC). Both types of line stimuli have approximately 1.7 deg of stimulus length, 4 c/deg of shape-frequency and approximately 3 c/m2 of luminance. The threshold measurement was conducted in separate sessions for the two types of line stimuli. If vernier- and curvature-detection tasks were mediated by, at least partially a common mechanism, the two types of stimulus would produce comparable results, and we actually obtained such results. The detection threshold for the two types of stimuli were quite comparable. These results demonstrate that curvature detection and vernier task share common mechanism.
Meeting abstract presented at VSS 2017