The idea is to practice variations of the skill you want to master instead of practicing same repetitions over and over. Actual paper is unfortunately behind paywall:<p><a href="http:&#x2F;&#x2F;www.sciencedirect.com&#x2F;science&#x2F;article&#x2F;pii&#x2F;S0960982215015146" rel="nofollow">http:&#x2F;&#x2F;www.sciencedirect.com&#x2F;science&#x2F;article&#x2F;pii&#x2F;S0960982215...</a>