Fig. 1. Stimulus positions and escape directions.

Vertical and horizontal eccentricities of the stimulus (ξ and Φ) are represented with concentric circles and radial lines, respectively. The frog is located at the center of the concentric circles facing 0° (upward on diagram). The stimulus position relative to the animal is represented by a large dot. The escape direction is represented by a bar extending from the dot. The bars seem to orient radially from the center of the concentric circles.