One hand helps the other: development of bimanual coordination in wild Sapajus libidinosus

Author(s)

Guilbert Rodrigues de Araujo

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Psicologia (IP/SBD)
• Defense date: 2023-04-12

Examining board members

Patricia Izar Mauro; Raphael Moura Cardoso; Rogerio Grassetto Teixeira da Cunha

• Advisor: Patricia Izar Mauro

Abstract

The coordinated use of the hands to explore the environment is a milestone in primate evolution. The characteristics of the primate hand allow the execution of skillful uni and bimanual actions, which have attracted the interest of researchers since the 19th century. Nowadays, the way pri-mates use their hands has been a window to investigate the motor and cognitive evolution of different species, including humans. From this perspective, the objective of the present project was to investigate for the first time, through a longitudinal approach, the emergence and devel-opment of bimanual coordination and postural control in wild infants of capuchin monkeys (Sapajus libidinosus), a Neotropical primate that draws attention for its rich repertoire of ma-nipulative skills. We tested the hypotheses that the acquisition of postural control, estimated by the onset of sitting, is a requirement for the emergence of bimanual actions and that the fre-quency and diversity of bimanual actions increase with age. To this end, we observed eight infants (from birth to the 12th month of life) of a population of Capuchin monkeys (Sapajus libidinosus) that lives in Fazenda Boa Vista (FBV), an area of the caatinga/cerrado ecotone in northeastern Brazil, in the city of Gilbués, southern Piauí. The immatures of this population have been followed by recordings for over ten years. The animals are habituated to human presence and the identity of the individuals is well known. We transcribed 3220 minutes of video distributed among the eight infants. We recorded at which period of early development the bimanual behaviors and the sitting posture first appeared, and described their rate of occurrence over the first twelve months of life. The bimanual actions appeared in the second month of life for most infants. In contrast, we observed sitting infants beginning in the third month of life. Therefore, the acquisition of postural control was not a requisite for the execution of bimanual actions, partially rejecting the first hypothesis. The infants Sapajus libidinosus from FBV, while incapable of sitting, found surfaces in the environment that provided sufficient postural support to liberate the upper limbs for manipulation. After acquiring postural control, they were able to differentiate the role of each hand during actions and expand their bimanual repertoire. The diversity and frequency of bimanual actions increased for most of the first year of life, support-ing the second hypothesis. In this study, we gather novel data on the development of bimanual coordination and acquisition of postural control in wild capuchin monkeys (Sapajus libidino-sus). Although capuchin monkeys in recent decades have become an important comparative model in investigating the evolution and ontogeny of manipulative skills in humans, the topics investigated in this study had not received adequate attention. We show that capuchin monkeys share many parallels with humans in bimanual development, key knowledge in future compar-ative approaches. (AU)

• FAPESP's process: 20/13930-0 - Development of hand use in a wild tool using primate (Sapajus libidinosus)
• Grantee: Guilbert Rodrigues de Araujo
• Support Opportunities: Scholarships in Brazil - Master