PERFORMANCE ON 2-FINGER CHORDS - PRACTICE EFFECTS AND ADVANCE INFORMATION

This study was designed to analyze the informational processes that pr ecede simultaneous two-finger movements, as a function of finger pairi ng, practice, and advance information. Subjects had to press buttons w ith one or two fingers, indicated by a visual signal. In Experiment 1, reaction time (RT) and performance errors were recorded for 10 one-fi nger and 45 two-finger responses, as a function of practice. RT analys is revealed a temporal overlap of response selection and programming o perations when the two fingers were on the same hand or when they were symmetric fingers of two different hands. In contrast, when two non-s ymmetric fingers had to be moved simultaneously, informational process es dedicated to the two responses occurred in succession. The pattern of substitution errors indicated the existence of homologous coupling during the selection of one finger from each hand. Practice resulted i n a shortening of RT only for non-homologous two-finger responses, and a decrease in error rate. In Experiment 2, subjects were provided wit h a preparatory signal indicating which finger(s) were to be used, eit her none, one, or two. RT decreased as a function of the number of pre cued fingers. Finger pairing no longer had an effect on RT when the tw o fingers were known in advance. The RTs recorded in the case of parti al advance information suggested that the programming of a within-hand two-finger response is a holistic process, whereas the programming of a cross-hand response involves two sets of operations that may be at least partially run in parallel for symmetric-finger responses.