Abstract
The detection and recognition of combinations of lines and curves composing simple shapes is a primary function of the human visual system. Previously, researchers have used circular contours with sinusoidal deformation of the radius (radial frequency (RF) patterns) to investigate the underlying processing involved in simple shape perception. It was suggested that these patterns exhibited global processing, improvement in detection of modulation for larger extents of modulated contour which could not be accounted for probabilistically. However, recent research has questioned the global processing of RF patterns (Baldwin, Schmidtmann, Kingdom, & Hess, 2016) and suggested that processing of these patterns is similar to that of modulated lines (Mullen, Beaudot, & Ivanov, 2011). The current study investigates these claims using fixed phase (where the local elements have spatial certainty), and random phase (where the local elements have spatial uncertainty) for both RF patterns, and modulated lines. Thresholds were collected for eight naïve observers and compared to probability summation estimates calculated using both high threshold theory and signal detection theory. Results demonstrated strong evidence for the global processing of random phase RF patterns and evidence for an interaction between local and global cues for fixed phase RF patterns. We also found an increase in sensitivity between 1, and 2 cycles of modulation, but not between 2, and 3 cycles of modulation for the modulated line stimuli. The results provide further evidence for the global processing of random phase RF patterns and indicate that RF patterns and modulated lines are processed differently.
Meeting abstract presented at VSS 2017