Strategy transitions during cognitive skill learning in younger and older adults: effects of interitem confusability.

Groups of young and old adults were trained for four sessions on a set of 24 alphabet-arithmetic problems. Problem sets were either highly confusable or highly distinct. Power-function and mixture-model fits to the means and standard deviations of the acquisition data, resolved at the participant problem level, were compared. "Shallow" power functions signaled that a problem was computed throughout training; "humped" mixture functions signaled a shift from slow computed solutions to fast retrieved solutions. Not surprisingly, shifts to retrieval occurred later for confusable problems, but there were also fewer shifts in that condition. Failures to shift, even after extended practice, suggest that retrieving problem solutions is an elective strategy, and not an automatic concomitant of skill training. Participants can be viewed as choosing between strategies that trade off benefits in speed against costs in accuracy. Older adults showed few retrieval solutions in either condition, perhaps because of their emphasis on accuracy.