Do rhesus monkeys (Macaca mulatta) perceive illusory motion?

Agrillo C., Gori S., Beran M.J. (2015). Do rhesus monkeys (Macaca mulatta) perceive illusory motion? Animal Cognition


During the last decade, visual illusions have been used repeatedly to  understand similarities and differences in visual perception of human and  non-human animals. However, nearly all studies have focused only on illusions not related to motion perception, and to date, it is unknown  whether non-human primates perceive any kind of motion illusion. In the  present study, we investigated whether rhesus monkeys (Macaca mulatta)  perceived one of the most popular motion illusions in humans, the Rotating  Snake illusion (RSI). To this purpose, we set up four experiments. In  Experiment 1, subjects initially were trained to discriminate static versus dynamic arrays. Once reaching the learning criterion, they  underwent probe trials in which we presented the RSI and a control  stimulus identical in overall configuration with the exception that the order of the luminance sequence was changed in a way that no apparent  motion is perceived by humans. The overall performance of monkeys  indicated that they spontaneously classified RSI as a dynamic array.  Subsequently, we tested adult humans in the same task with the aim of  directly comparing the performance of human and non-human primates  (Experiment 2). In Experiment 3, we found that monkeys can be successfully  trained to discriminate between the RSI and a control stimulus. Experiment 4 showed that a simple change in luminance sequence in the two arrays  could not explain the performance reported in Experiment 3. These results  suggest that some rhesus monkeys display a human-like perception of this  motion illusion, raising the possibility that the neurocognitive systems  underlying motion perception may be similar between human and non-human