Publication detail

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 wirelike 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).

@article{vandekerckhove_etal:2007:concavity,
    title   = {{T}he concavity effect is a compound of local and global effects},
    author  = {Vandekerckhove, Joachim and Panis, Sven and Wagemans, Johan},
    year    = {2007},
    journal = {Perception \& Psychophysics},
    volume  = {69},
    pages   = {1253--1260}
}