The authors of this paper used an ethological approach to test the hypothesis that practice-related refinements of multiple behavioural features would be independently predictive of motor learning.
Perry, Christopher M., Tarkeshwar Singh, Kayla G. Springer, Adam T. Harrison, Alexander C. McLain, and Troy M. Herter. "Multiple processes independently predict motor learning." Journal of NeuroEngineering and Rehabilitation 17, no. 1 (2020). doi:10.1186/s12984-020-00766-3.
This small study observed the motor learning effects of allowing small choices by individuals.
An, Jongseong, Rebecca Lewthwaite, Seungmin Lee, and Gabriele Wulf. "Choice of practice-task order enhances golf skill learning." Psychology of Sport and Exercise 50 (2020), 101737. doi:10.1016/j.psychsport.2020.101737.