Sensorimotor synchronization (SMS) is especially apparent¿and therefore readily studied¿in musical settings, as most people are naturally able to perceive a musical beat and synchronize to it (e.g. by tapping a finger). SMS processes have been tested extensively using pseudo-musical pacing signals, so we chose to extend this by using naturalistic, expressively timed piano music, characterized by slight tempo fluctuations for artistic interpretation. Previous research has also shown that people vary greatly in their SMS abilities. Given the dynamic nature and variability of SMS, we hypothesized that individual differences in working memory and auditory imagery¿both fluid, cognitive processes¿would predict SMS at two levels: 1) asynchrony (a measure of synchronization error), and 2) anticipatory timing (i.e. predicting, rather than reacting to beat onsets). In Experiment 1a, participants (N = 36) completed two working memory tests, a tempo imagery test, a pitch imagery test, and a self-report test of auditory imagery with separate subscales for vividness (clarity of an image) and control (ability to alter an image). They were then tested in a SMS-tapping task. In Experiment 1b, the same set of tasks was given to highly trained musicians. In Experiment 2, participants were given an expressive timing perception test to see the extent to which the cognitive variables related to perception without action. Hierarchical regression models were used to assess the contribution of the cognitive variables to SMS. Results showed dissociations among imagery types as they relate to asynchrony, perception, and suggest a role for working memory in anticipatory timing. Musicians performed better on the SMS task, but showed fewer correlations between the cognitive variables and SMS. These results suggest that in nonmusicians imagery for pitches and temporal patterns is important for synchronizing to an auditory stimulus, but working memory is implicated in strategically synchronizing via anticipation of beat onsets
