Figure 2.

The stimuli. Using measurements from fruit in a Ugandan rainforest (e.g. panel a: samples of unripe, green, and ripe, yellow, Chrysophyllum albidum), we chose segments yellow pepper as targets and green pepper as distractors (b), because they have similar reflectance spectra (c) and chromatic properties (Figure 3). The “fruit” stimuli (b) subtended approximately 2, 0.5, 0.25 and 0.16 degrees of visual angle for distances 1, 4, 8, 12 m. In panel (c), thin orange and green lines are ripe and unripe Ugandan fruit Chrysophyllum albidum, orange and green thick lines are “ripe” and “unripe” peppers used as experimental stimuli.