The concavity effect is a compound of local and global effects.
Using a change detection paradigm, Barenholtz, Cohen, Feldman, and Singh (2003) found that changes in concave regions of a contour are more easily detected than changes in convex regions. In a series of three experiments, we investigated this concavity effect using the same paradigm. We observed the effect in wire-like stimuli as well as in silhouettes (Experiment 1) and in complex, smoothed images as opposed to angular polygons (Experiment 2). We also observed a systematic effect of the magnitude of the change (Experiment 1). Furthermore, we find that the effect cannot be attributed to either local or global processing effects, but rather to a combination of both "mere" concaveness and an effect due to changes in the perceived part structure of the stimulus object (Experiment 3). For our data analysis, we used a nonparametric bootstrap method, which greatly increases sensitivity (compared to more traditional analyses like ANOVA).
University of Leuven, Department of Psychology, Leuven, Belgium. joachim.vandekerckhove@psy.kuleuven.be
Joachim
J
Vandekerckhove
Sven
S
Panis
Johan
J
Wagemans
D006801:Humans; D011601:Psychophysics / Q000379:methods*; D014796:Visual Perception