Visual expertise does not predict the composite effect across species: a comparison between spider (Ateles geoffroyi) and rhesus (Macaca mulatta) monkeys.
Humans are subject to the composite illusion: two identical top halves of a face are perceived as "different" when they are presented with different bottom halves. This observation suggests that when building a mental representation of a face, the underlying system perceives the whole face, and has difficulty decomposing facial features. We adapted a behavioural task that measures the composite illusion to examine the perception of faces in two nonhuman species. Specifically we had spider (Ateles geoffroyi) and rhesus monkeys (Macaca mulatta) perform a two-forced choice, match-to-sample task where only the top half of sample was relevant to the task. The results of Experiment 1 show that spider monkeys (N=2) process the faces of familiar species (conspecifics and humans, but not chimpanzees, sheep, or sticks), holistically. The second experiment tested rhesus monkeys (N=7) with the faces of humans, chimpanzees, gorillas, sheep, and sticks. Contrary to prediction, there was no evidence of a composite effect in the human (or familiar primate) condition. Instead, we present evidence of a composite illusion in the chimpanzee condition (an unfamiliar primate). Together, these experiments show that visual expertise does not predict the composite effect across the primate order.
Taubert
Jessica
J
The Centre for the Integrative Study of Animal Behaviour, Macquarie University, Sydney, NSW 2109, Australia. jtaubert@psych.usyd.edu.au
Parr
Lisa A
LA
D000704:Analysis of Variance; D000818:Animals; D053819:Atelinae / Q000502:physiology*; D001288:Attention / Q000502:physiology; D016009:Chi-Square Distribution; D004193:Discrimination Learning / Q000502:physiology; D005145:Face; D005149:Facial Expression; D005260:Female; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D009903:Optical Illusions / Q000502:physiology*; D009949:Orientation / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology