Individual differences in rhythmic ability: Behavioral and neuroimaging investigations.

Rhythmic abilities vary widely in the general population, but little is known about the factors that give rise to this variability. One factor may be musical training. Another may be differences in auditory short-term memory (STM) capacity (the amount of auditory information that can be remembered over a few seconds). Finally, as rhythms with temporal regularity (e.g., a beat) are more easily remembered and reproduced, individual differences in sensitivity to regularity may contribute to rhythmic ability differences. To investigate the contribution of each of these factors to rhythm reproduction ability, we assessed auditory STM capacity (using digit and pseudoword span tasks), beat sensitivity (using the Beat Alignment Test [BAT]), and levels of musical training. Rhythmic ability was measured using a rhythm reproduction test. We found that STM capacity, beat sensitivity, and musical training predicted unique variance in rhythm reproduction performance. Using functional magnetic resonance imaging (MRI), we assessed individual differences in brain activity related to the previously measured auditory STM capacity, BAT score, musical training, and rhythmic ability, while participants performed a rhythm discrimination task. Activity in posterior superior temporal gyrus and middle temporal gyrus negatively correlated with auditory STM capacity. Positive correlations with BAT score were found in leftangular gyrus, supplementary motor area, and premotor cortex. Positive correlations with musical training were observed in leftposterior middle temporal gyrus, and negative correlations were observed in leftsupplementary motor area. The findings implicate both auditory and motor areas in factors that underlie individual differences in rhythmic ability.Keywords: music, rhythm, timing, auditory perceptionSupplemental materials: http://dx.doi. org/10.1037/a0031188.suppAnecdotally, rhythmic ability is thought to vary widely across healthy individuals. Several individuals report having "no sense of rhythm," and previous work has investigated individuals with specific rhythmic impairments or "beat deafness" (Foxton, Nandy, & Griffiths, 2006; Phillips-Silver et al., 2011). However, little work has specifically investigated and reported on the range of rhythmic ability in the general population, and the underlying causes of individual differences in rhythmic ability have yet to be fully elucidated. Three factors seem like promising candidates and form the focus of the current study. The first is auditory short-term memory (STM) capacity, as this has been shown to relate to rhythm reproduction, discrimination, and synchronization ability in previous work (Bailey & Penhune, 2010; Saito, 2001; Wallentin, Nielsen, Friis-Olivarius, Vuust, & Vuust, 2010). The second is sensitivity to the presence of regular temporal structure (e.g., beat structure). Rhythms that have a regular temporal structure are discriminated and reproduced better than irregular rhythms (Grahn & Brett, 2007; Patel, Iversen, Chen, & Repp, 2005); therefore, it is likely that individuals with better ability to detect this regularity (when it exists) should do better on rhythm tasks. The third factor is musical training. However, musical training may exert an indirect effect by influencing the aforementioned factors: musical training is associated with better auditory STM span (Bailey & Penhune, 2010; Saito, 2001; Wallentin et al., 2010), and seems likely to improve beat detection, although this has not been tested directly. Music also may have direct effects on rhythmic ability, such as providing a range of strategies for accurate rhythmic encoding and reproduction. The potential role of each of these factors will now be described and considered in more detail.Auditory STMMost models of auditory STM posit two components: one involved in representing the to-be-remembered items and the other involved in maintaining those representations (Baddeley & Hitch, 1974; Cowan, 1999). …