„The impact of variability depends on whether it is relevant to the task or not (arguably, the colour of the tennis court is not relevant to serving practice). But according to the ‘Mr. Miyagi principle’ (inspired by the 1984 classic movie Karate Kid), practicing seemingly unrelated skills (such as waxing cars) may actually benefit learning of other skills (such as martial arts).“

Limor Raviv, Max Planck Institut