Capuchin Monkeys (Sapajus spp.) Take Advantage of Tactile Information to Visually Recognise Different Object Features

Although diurnal primate species mainly rely on sight to gather information from the environment, touch is both the first sense to develop and by far the most extensive in Primates. Systematic studies investigating the integration of information coming from the sensory systems of sight and touch are sparse in non-human primates. To date, little is known about possible enhancement effects due to the synergy of these two sensory modalities. Here, we investigated in capuchin monkeys ( n = 12) whether manipulating objects and retaining tactile memory enhanced visual discrimination learning for larger-scale (i.e. size, shape) and smaller-scale (i.e. surface) object features. A two-alternative forced choice task was used to train capuchins to visually select a rewarded stimulus between 2 wooden objects differing in size, shape or surface. Object pairs were presented in 2 conditions: the Sight condition prevented capuchins from haptically perceiving the object features; the Sight & Touch condition allowed them to gain tactile information about the object chosen by sight. Our results showed that the availability of tactile information (Sight & Touch condition) accelerated learning speeds for visual discrimination of object size, shape and surface. Overall, our data demonstrated that the acquisition of tactile information about an object's features allowed capuchins to achieve high levels of visual accuracy faster. These results suggest that information from touch influenced perceptual and/or attentional processes in visual modality and encouraged further investigation on how manual exploration affects object recognition.