Capuchins’ manual skills: precision and asymmetry
Those who carefully observe capuchins, certainly appreciate their precision in moving objects. Although they fail the tip-to-tip grip seen in humans (and not for not being able but for anatomical reasons), capuchins possess functional precision grips, more than those showed by other New World species. Moreover, they have a favorite hand to rely on, when performing complex motor tasks.
Capuchin monkeys have the greatest degree of manual dexterity of all New World monkeys. Although their prehensile hand has a pseudo-opposable thumb, they possess both a precise and powerful grip and frequently make use of unimanual and bimanual forms of precision handling. In our Primate Center, we studied different aspects regarding hand use. We found that to perform grasping actions, capuchins use a wide variety of grips, which often involve distal areas of the hand. In particular, the precision grip most frequently used to grasp small food items, involves the distal lateral areas of the thumb and the index finger.
We believe that wild capuchins acquire their manual dexterity by acting on substrates, and by combining an object with the natural substrate, activities that they perform on a daily basis during extractive foraging. On the other hand, captive monkeys can earn the accolade “dexterous”, if trained with tasks involving the fine use of hands. Moreover, we found that both simple and complex grasping actions, induce the hand preference at an individual level, whereas only tasks involving more complex motor patterns are likely to induce an asymmetry in the distribution of lateral bias at group level. But we are still far from understanding the origins or the functional significance of motor asymmetry in non-human primates; nor if these asymmetries are similar to those found in humans.
A video on wild capuchins’ manual skills during nut cracking and food processing was presented at the temporary exhibition "La Mano – Arto, arte, artefatti” (July 27, 2013 – January 20, 2014) organized by MUSE (Museo delle Scienze di Trento). A contribution was also realized for the official catalogue of the exhibition (pdf) presented during the evening opening of MUSE, the day October 23, 2013.
Filmed by Alessandro Albani and edited by Elisabetta Visalberghi and Valentina Truppa/Ethocebus project
Scientific publications
