Acquisition of hierarchical control in skilled action sequencing

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A critical issue in cognitive science is understanding how behavior unfolds in time. Most human behaviors, from walking and talking, to driving, typing and playing instruments, consist of a series of ordered actions. Little is known concerning how people learn the serial ordering of actions and how this ability changes with expertise. This investigation uses the task of skilled typing to study how high- and low-level cognitive processes interact to allow typists to order their keystrokes rapidly and accurately. Typing is a useful model system for this purpose because experts are plentiful and typing performance can be measured precisely in terms of keystroke timing and errors. Prior studies have shown that typing skill is controlled hierarchically by two processing loops: an "outer loop" turns ideas into words and sentences and an "inner loop" translates words into motor movements for executing individual keystrokes. Three related projects test how these loops control serial ordering across levels of typing skill. Project 1 uses a large-scale web-based approach to quantify how novices and experts become sensitive to the statistics of natural keystrokes and learn to optimize typing performance for predictable letter patterns. Project 2 explores how the inner loop becomes gradually connected to the outer loop, allowing verbal codes used for language production to control serial ordering of fingers on the keyboard. Project 3 tests how the inner loop schedules the timing of individal keystrokes after it has received word-level instructions from the outer loop. Typing, especially on computers and smartphones, has become an indispensable modern skill. This work can provide new statistical signatures of typing skill that can be used to promote rapid skill acquisition. The science of typing can also serve as a model for investigating other domains that rely on hierarchical control loops to accomplish complex serial ordering, such as playing a musical instrument, assembly work, and interactive technologies. The project also provides training opportunities for graduate and undergraduate students at an institution that serves several minority and underrepresented groups.