Frankly, I'm completely mystified by this paper. It appears to be built on a circular and self-contradictory logic. The paper compares hours of music practice

Frankly, I'm completely mystified by this paper. It appears to be built on a circular and self-contradictory logic. The paper compares hours of music practice to scores in the Swedish Musical Listening Test (SMLT). It finds no significant correlation, concluding that there is no causal relationship between musical practice and musical skill. The SMLT does not directly measure practical musical skills, but is treated by the authors as a valid proxy measure because it correlates with hours of musical practice (Ullén et al, 2014). Practice does not improve musical ability because hours of practice are not correlated with scores in the SMLT. The SMLT is a valid proxy measure of musical ability because scores correlate with hours of practice. See the problem? Ullén, F., Mosing, M. A., Holm, L., Eriksson, H., & Madison, G. (2014). Psychometric properties and heritability of a new online test for musicality, the Swedish Musical Discrimination Test. Personality and Individual Differences, 63, 87–93. (10.1016/j.paid.2014.01.057)