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Intelligence correlates with accuracy in various timing tasks. Such correlations could be due to both bottom–up mechanisms, e.g. neural properties that influence both temporal accuracy and cognitive processing, and differences in top–down control. We have investigated the timing–intelligence relation using a simple temporal motor task, isochronous serial interval production (ISIP), i.e. hand/finger movements with a regular beat. ISIP variability is egatively correlated with intelligence and we have previously argued, based on indirect evidence, that this relation has a bottom–up component. Here, we investigate this question using an experimental within-subject design in two samples (n=38 and n=95 participants, respectively). ISIP was performed under two conditions. In the first condition (Low Motivation), the participants were told that measurements were being made to familiarize them with the task and to calibrate the equipment. In the second condition (High Motivation), the participants were told that the performance would be evaluated and used for scientific analysis, and they were given a monetary reward depending on how accurately they performed. Temporal accuracy in the ISIP was higher during High Motivation than during Low Motivation. In both samples, correlations between ISIP variability and intelligence were similar for both conditions. General linear models with ISIP variability measures as dependent variables, condition (Low Motivation or High Motivation) as a repeated-measures variable and intelligence as a betweensubject variable, revealed a significant effect of intelligence, but no effects of incentive, nor of the intelligence×incentive interaction. We conclude that motivationally driven top–down mechanisms can influence ISIP performance, but that they play no major role for correlations between temporal accuracy in ISIP and intelligence. These results provide further support for that bottom–up mechanisms are involved in relations between temporal accuracy and intelligence.