Ss chose on each trial between betting on the left or the right key of a kind of slot machine. One group practices where one key is always correct, switches then to a randomly arranged 50-50 payoff and then returns to practice with one key always correct. Another group begins with the 50-50 series. The speed with which the Ss learn the final set of probabilities is such that having had initial experience with one key always paying off is an advantage over having no such experience. It appears that the effect of prior experience can be mediated through the kind of strategy of choices induced by this experience and the appropriateness of this experience for later learning. The speed of final learning varies with the arrangement of the 50-50 phase: whether there is a predominance of long or short runs. 20 references. (PsycINFO Database Record (c) 2006 APA, all rights reserved).