Figure 1.

Influential neighbours. (a) Adjustable interaction range R_a for individuals 1, 2 and 3. The adjustable range is shorter if the crowding is denser (around individual 3); individuals in the figure always have seven interaction neighbours. (b) Schools with occluded perception [16]. Individuals in dark black are those neighbours with whom there is interaction. Individuals in dark are located in interaction range. Individuals in light grey are outside the field of view. γ indicates the blind angle. (c) Behavioural areas of avoidance (separation), alignment and attraction (cohesion) with a dead angle at the back, γ.