Adjustment to a complex visuo-motor transformation at early and late working age.

Age-related changes of adjustment to visuo-motor transformations were studied for a complex transformation modelled after those encountered in laparoscopic surgery. Movement times of aimed movements were initially almost identical for the two age groups and diverged in the course of practice. In test phases without visual feedback, no age-related variation of the adaptive shifts and after effects of amplitude and curvature of hand movements were observed, but only of their direction. Directional adaptive shifts were bimodally distributed, with one mode near to perfect adaptation ('adapters') and the other one near to absence of adaptation ('non-adapters'). Among the young participants, adapters were more frequent than among the old participants. These findings extend previous results on age-related changes of adjustment to simple transformations to complex transformations. They are consistent with the claim that age-related changes of adjustment to visuo-motor rotations come about primarily by impairments of strategic corrections. A link is established between basic-research findings and transformations encountered outside the laboratory: what suffers at higher working age is explicit knowledge of visuo-motor rotations and the strategic corrections based on it. This suggests the provision of opportunities for explicit-knowledge acquisition for those of a higher age.