Distinct modes of executing movement sequences: Reacting, associating, and chunking

Responding to individual key-specific stimuli in entirely unfamiliar keying sequences is said to involve a reaction mode. With practice, short keying sequences can be executed in the chunking mode. This is indicated by the first stimulus sufficing for rapid execution of the entire sequence. The present study explored whether an associative mode develops also in participants who practice short keying sequences. This associative mode would involve priming by earlier events of responses to external stimuli, and is believed to be responsible for skill in the Serial Reaction Time task. In the present study participants practiced two discrete 6-key sequences. In the ensuing test phase, participants were prevented from using the chunking mode by including two deviant stimuli in most sequences. The results from the remaining – unchanged – familiar sequences confirmed that participants no longer used the chunking mode, but as predicted by associative learning these sequences were executed faster than unfamiliar sequences.

► Movement sequences can be learned by two mechanisms.
► The sequencing mode is based on motor chunks.
► The associative mode is based on priming forthcoming reactions.
► The associative mode may be overshadowed by the chunking mode.