Which are the features of the TUBE task that make it so efficient in detecting manual asymmetries? An investigation in two Cercopithecine species (Cercopithecus neglectus and Cercocebus torquatus) (original) (raw)

2013, Journal of Comparative Psychology

In the last decade, the TUBE task has been repeatedly shown to be highly efficient in detecting manual asymmetries that are strong hand preferences reflecting hemispheric specialization, in non human primates. The TUBE task was thus classified as a high-level task, presumably because it involves bimanual coordination. However, this task also requires a precise action made by digit(s), which may also be a crucial feature in eliciting manual asymmetries. In the present study, we compared hand preferences for a new TUBEunimanual task and the classic TUBE-bimanual task, both performed mostly by using the forefinger, in 12 guenons (De Brazza's monkey: Cercopithecus neglectus) and 18 mangabeys (red-capped mangabey: Cercocebus torquatus). We found a relationship between hand preferences exhibited for the two tasks, suggesting that precise use of the forefinger may induce the activation of a specialized hemisphere in both the TUBE-unimanual and the TUBE-bimanual task. However, we showed that the strength of manual laterality was higher in the TUBE-bimanual task than in the TUBE-unimanual task, indicating that bimanual coordination may enhance the expression of hand preferences. We propose that the TUBE-bimanual task is highly efficient in detecting hemispheric specialization because bimanual role differentiation would make precise digit use highly skillful. Finally, we revealed species differences in hand use, especially in females: the most arboreal species, De Brazza's monkeys, increased left-hand use from the TUBE-unimanual to the TUBEbimanual task whereas the most terrestrial species, red-capped mangabeys, increased right-hand use. We thank Maxime Hervé for helpful advices on statistical issues. We are grateful to Cécile Schweitzer and Agathe Laurence for polishing the methodology for the classic TUBE task in guenons and mangabeys, respectively. We thank three anonymous reviewers for valuable suggestions to improve the article.