Development of motor cooperation through joint-action in middle childhood: a behavioral study

The development of the abilities to behave in a joint-action so far has been investigated only in infants and preschoolers (Tollefsen, 2005; Brownell et al. 2006). To our knowledge, no experiments have been carried out yet to investigate how and when the ability related to successfully perform a joint-action does develop during middle childhood. Since this developmental period is critical for the large changes in motor dexterity, cognition, and sociality (Hartup, 1984; Fischer & Silvern, 1985; Hale, 1990), we thought that it would have been also crucial for the refinement of those skills required for complex forms of motor coordination, such as those required during joint-action. Thus, we tested couples of age- and gender-matched children (5-9 years) and adults while they performed a center-out videogame, in which the same action (moving a cursor on a screen through an individual isometric joystick) could be performed i) alone, ii) in a coordinate fashion with the partner (joint-action task), iii) coordinating with a computer, which reproduced the partner’s trajectories. It was found that the performance in the joint-action task improved during development, but that there was a critical “jump” between 7-8 years, in which the performance during the joint-action improved rapidly, reaching for most parameters the level of adults at 9 years . Importantly, the increase in the joint-action performance did not simply reflect the maturation of the motor skills underlying single-action. Since 7-8 years, the performance benefited from the presence of an interaction with a real partner (“cooperation benefit”), as compared to the simple coordination with the computer. The analysis of spatial-temporal parameters of behavior showed the presence of a shift in the strategies for the movement control during the joint-action, from feedforward (around 6 years) to feedback-based (around 9 years). We thought that older children gradually learned to adjust their movements with respect to those of their partners through the use of feedback corrections, which allowed them to perform an online control of their partners’ trajectories, a strategy made possible by the long movement times that characterized the task performance. The cognitive development and the changes in motor control occurring around 7-8 years are discussed as possible factors mediating the growth in the fine motor adjustment responsible of the improvement in the joint performance.