Figure 2: The probability distribution function $p(\psi, \theta)$ represents the distribution of the different geometrical arrangements of edges' angles, which we call a chevron map. We show here the histogram for non-animal natural images, illustrating the preference for co-linear edge configurations. For each chevron configuration, deeper and deeper red circles indicate configurations that are more and more likely with respect to a uniform prior, with an average maximum of about $3$ times more likely, and deeper and deeper blue circles indicate configurations less likely than a flat prior (with a minimum of about $0.8$ times as likely). Conveniently, this chevron map shows in one graph that non-animal natural images have on average a preference for co-linear and parallel edges, (the horizontal middle axis) and orthogonal angles (the top and bottom rows),along with a slight preference for co-circular configurations (for $\psi=0$ and $\psi=\pm \frac \pi 2$, just above and below the central row). We compare chevron maps in different image categories in Figure 3. Go back to manuscript page.

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