Considerable research has been devoted to understanding how intrinsic motivation can augment the learning of motor skills. Many manipulations targeting intrinsic motivation have led to improved learning, but the mechanisms underlying this effect are not known. Replicating a previous study, we manipulated intrinsic motivation by giving one group self-control over the difficulty of practice, while a control group was yoked to that schedule. We collected measures of intrinsic motivation, engagement, and physiological measures related to dopamine (spontaneous eye-blink rate; sEBR) and approach motivation (frontal alpha asymmetry; FAS) to understand mechanisms underlying learning effects. Although the effect of self-control was not significant in the current experiment, the overall result was statistically significant when combined with the results of our previous study. Overall, there is evidence for a benefit of self-control during practice, but the true effect-size is smaller than initially estimated. Furthermore, even though self-control led to increased intrinsic motivation in the current experiment, individual differences in motivation were not correlated with learning. Similarly, neither sEBR nor FAS were related to learning. Taking a cumulative view, these data suggest that self-control of practice is beneficial to both learning and motivation, but increased motivation does not appear to directly cause improved learning.