Abstract : The purpose of the study was to compare the rate of learning-set formation by monkeys that had previously been pretrained on the win-stay component of the learning-set strategy (WS group) with others that had pretraining on the lose-shift component (LS group). Negative transfer is discussed which resulted from generalized tendencies to perseverate or shift, (WS and LS groups, respectively) regardless of response outcome. The former tendency dissipated relatively rapidly, while the latter persisted very markedly throughout the 400 problem learning set series. Learning-set formation requires a balance between the win-stay and lose-shift components; however, the optimal ratio is unknown. (Modified author abstract)