Tamarin monkeys use advanced action planning, similar to human adults

What is it about?

Despite their low manual dexterity, Cotton Top Tamarins (South American primates) are very efficient motor planners. Tamarins were presented with a horizontal dowel where one end was baited with food. When grasping the dowel, tamarins used efficient radial grasps, where the food could immediately be directed towards their mouth with no adjustment. When given a similar task, chimpanzees are not efficient motor planners, despite their high dexterity.

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Photo by Sandy Millar on Unsplash

Photo by Sandy Millar on Unsplash

Why is it important?

One of the hallmarks of complex motor planning in humans involves grasping objects in preparation for future actions, termed second order motor planning. This ability has an extended developmental trajectory in humans and is also shared with nonhuman primates. Here, we presented 7 cotton-top tamarins with a dowel task that has prompted variable grasping behaviors for some primate species. Tamarins could either use an efficient grasp to bring food stuck onto the end of a dowel to their mouth (radial grasp) or an inefficient grasp that required repositioning (ulnar grasp). The tamarins were very consistent in their use of radial grasps. These data support the morphological constraint theory suggesting that species with limited dexterity (inability to perform precision grasps) may demonstrate more consistent second-order motor planning due to the increased cost of inefficient grasping postures.

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