Testing for an Optimal Task Difficulty of Skill Acquisition in Golf Putting

The Challenge Point Framework suggests that an optimal difficulty exists for promoting motor learning. However, the "sweet spot" has yet to be found, potentially due to methodological differences. Limitations of previous literature include (a) the lack of a standard metric to gauge task difficulty, (b) the lack of a standard dependent variable (as a raw score varies between different task difficulty levels), and (c) the lack of a definition of "optimal difficulty." To this end, the present study employed "success rate" as a measure of difficulty. For the dependent variable, the normalized performance and the coefficient of variation were used for group comparisons. To assess optimal difficulty, we considered two potential definitions: the improvement rate (the pattern of improvement) and the magnitude of learning. A total of 150 participants (M_age ± SD = 21.75 ± 2.21) were randomly and equally assigned to one of three groups: high (60-70%), medium (20-30%), and low success rate ( < 10%). Participants practiced golf putting for 50 trials, followed by a 24-hour retention test. Our results showed that the pattern and magnitude of learning did not differ, suggesting that no optimal difficulty existed in golf putting with the present design. Future studies should employ consistent metrics and definitions of optimal difficulty to facilitate meaningful comparisons between experiments. We discussed the need for further discussion to address and overcome existing methodological and conceptual limitations and inconsistencies.