ABSTRACT
Lashley introduced a number of arguments that sequences of human motor activity are guided by plans and not by peripheral or central associations between one event and the next. Although there is some evidence in favor of an associationist position, a large body of evidence has been supportive of Lashley's seminal ideas. Moreover, a variety of paradigms including reaction time, pauses between successive motor acts, and transfer of learning have emphasized two concepts that characterize these plans or motor programs. First, the plans that guide activity are hierarchical in nature. Second, many sequence representations can be regarded as modular in that they are separable from the muscular system of initial learning and can be interfaced with various other modules to produce novel actions. Hierarchic and modular components are thus viewed as important components for any model of sequencing. One particular computational model developed by Jordan is described and analyzed in terms of how well it meets this criterion.
