Subjects chose between sequences of one syllable (e.g., 19i/ vs. /bi/), two syllables (e.g., /gibi/ vs. /gubu/), and three syllables (e.g., /gibidi/ vs. gubudu/), when Iii sequences were signaled by high-pitched tones and lui sequences were signaled by low-pitched tones (high compatibility), or the reverse (low compatibility). Choice times were additively affected by sequence length and compatibility. A second experiment showed attenuated compatibility effects for sequences with different vowels in the first and second syllables. These results replicate previously reported results for choices between finger sequences, which suggests that the same programming methods are used in both output domains. Evidently, choices between response sequences can be achieved by selecting a distinguishing parameter and assigning it in a serial fashion to partially prepared motor subprograms.An emerging view of human movement control holds that abstract parameters are used in the programs for forthcoming movement sequences. For example, abstract timing information for movement sequences has been inferred from the fact that typing , writing , arm positioning (Armstrong, 1970;Shapiro, 1977), and walking (Shapiro, Zernicke, Gregor, & Diestel, 1981) exhibit invariant timing relationships among successive movement elements (see Rosenbaum, 1985;Schmidt, 1975). Similar sorts of invariances for force (Freund & Budingen, 1978;Ghez, 1979) have led to the proposal that force is another abstract parameter used in motor programming (Meyer, Smith, & Wright, 1982).Discovering abstract programming parameters raises the question of how the parameters are set during the programming process. Inhoff, Rosenbaum, Gordon, and Campbell (1984) addressed this question by conducting choice reaction-time (RT) experiments in which subjects chose between two homologous (mirror-image) fmger sequences cued by signals that were either compatibly or incompatibly mapped to the hands performing the sequences. Stimulus-response (S-R) compatibility was This paper is based on a Division ill examination (equivalent to a senior honors thesis) by the secondauthor and submitted to Hampshire College in partial fulfillment of the bachelor's degree. The research was supported in part by Grants BNS-8120104 and BNS-8408634 from the NationalScienceFoundationand ResearchCareer Development Award 1 K04 NS00942-{}I from the National Institute of Neurological and Communicative Disorders and Stroke to the first author. We thank Alice Healy, David Meyer, Lynne Baker-Ward, Judith Kroll, and an anonymous reviewer for helpful comments. Correspondence should be addressed to David A. Rosenbaum, School of Communications and Cognitive Science, Hampshire College, Amherst, MA 01002. manipulated by assigning the signal on the left to the left hand and the signal on the right to the right hand (high S-R compatibility), or the opposite (low S-R compatibility). In the first experiment, S-R compatibility and the length of the to-be-performed sequence had additive effects on the choice RT for the fi...