Object perception and masking: Contributions of sides and convexities

Object perception uses a variety of visual cues, including shape cues derived from sides and convexities. Two recent masking studies using radial frequency patterns have argued, respectively, for a predominant role of convexity [Habak, C., Wilkinson, F., Zakher, B., & Wilson, H. R. (2004). Curvature population coding for complex shapes in human vision. Vision Research, 44 (24), 2815–2823] or side information [Hess, R. F., Wang, Y. -Z., & Dakin, S. C. (1999). Are judgements of circularity local or global? Vision Research, 39, 4354–4360]. Here we resolve the controversy by separating the masks into their parts (e.g., convexities and sides), and measuring the relative masking influences of the different mask components. We found that both side and convexity information contribute to masking. However, masking due to side information was much less dependent on alignment compared to masking due to convexities. This supports a theory where convexities constitute a prime source of information for shape processing, and sides do also contribute but to a smaller extent.