A longitudinal study of prospective control in catching by full-term and preterm infants.

Prospective control when catching moving toys was studied longitudinally in full-term and preterm infants between the ages of 22 and 48 weeks. The toy's distance and time to the catching place and its velocity were explored as possible timing strategies used by infants to start their hand movement. The aim of the study was to find evidence for a shift in timing strategy and whether there were differences between full-term and preterm infants. In addition, it was investigated how infants continuously guided their hands to the toy and whether this guidance was influenced by their use of timing strategy. The toy approached the infants from the side with different constant velocities and constant accelerations. Results showed that there was little difference between full-term and preterm infants' use of timing strategies. Initially, infants used a distance- or velocity-strategy, possibly causing them to have many unsuccessful catches. After a shift to a time-strategy, infants appeared to increase the number of successful catches and performed longer and more functional tau-couplings between the hand and the toy. One preterm infant did not switch to a time-strategy, and frequently missed the moving toy. The same infant also showed less functional tau-coupling with non-controlled collisions between the hand and the toy. More follow-up research is needed to investigate whether problems with extracting the relevant perceptual information for action could be an early indication of later perceptuo-motor difficulties.