Fig. 2: Perception of motion salience in collective motions.

a Diagram of MS to quantify the relative movement changes of neighbor-\(j\) from the focal individual-\(i\)’s first-person view. b The anisotropic effect of motion perception in Eq. (1) mimics the idea that the perception capability diminishes as the focal individual’s first-person sight extends from the front to the back. c The anisotropic factor \(\alpha \ge 0\) in MS controls the fact of forward-oriented preference in biological perception. The \(x\)-axis indicates the heading between two vectors \({\hat{{{{{{\bf{v}}}}}}}}_{i}\) and \({\hat{{{{{{\bf{x}}}}}}}}_{ij}\), and \(y\)-axis corresponds to the second or third term of right-hand of Eq. (1). If \(\alpha=0\), we ignore the blind area of motion perception. With increasing \(\alpha \, > \, 0\), we assume that the ability of individual perceiving movements of around neighbors gradually narrows to the front vision.