Effects of Sequential Aspects of Learning History

in a series of five experiments, a number of similar operant classes, consisting of keystroke sequences on a computer keyboard, were learned and practiced in succession by human subjects. each experiment consisted of learning sessions spread over several days, separated by either elapsed time or interpolated sessions in which unrelated but similar operant classes were performed. the learning sessions were followed by a final test session in which the subjects were required to choose and perform one from presented sets of three operant classes. the test was designed to be stressful by the imposition of time pressure and certain other contingencies. in the test session, preference was commonly shown for operant classes from the first- and/or last-learned groups-termed primacy and recency effects respectively-with minimal preference for the middle groups. most subjects showed either primacy or recency effects, and relatively few showed both; the subjects that showed mainly recency effects also made the largest number of errors during initial learning of the last set of operant classes. in addition, certain noncriterial characteristics of these operants were measured. these revealed other effects, in particular the association of performance errors with both greater resurgence of older behavior patterns and greater numbers of new behavior patterns.