acta psychologica ELSEVIER Acta Psychologica 94 (1996) 59-85 From cognition to biomechanics and back: The end-state comfort effect and the middle-is-faster effect 1 David A. Rosenbaum a,*, Caroline M. van Heugten b, Graham E. Caldwell c a Department of Psychology, Moore Building, Pennsylvania State Universi~, Uniuersity Park, PA 16802, USA b Department of Psychology, University of Leiden, Leiden, The Netherlands c Department of Exercise Science, Unicersi~ of Massachusetts, Amherst, MA, USA Received 11 January 1995; revised 15 September 1995; accepted 9 November 1995 Abstract Consistent preferences for particular types of movement suggest criteria for movement selection. These can be important when, as is usually the case, infinitely many movements allow a task to be achieved. The experiments reported here were designed to identify the source of a strong preference observed in earlier object-manipulation studies. In those earlier studies, subjects usually grabbed objects to be moved from one location to another in a way that afforded a comfortable final posture rather than a comfortable initial posture (the end-state comfort effect). The comfortable final state usually allowed the forearm to be at or near the middle of its range of motion on the pronation-supination dimension. The hypothesis tested here was that the end-state comfort effect stemmed from an expectation that movements can be made more quickly in the middle of the pronation-supination range than at either extreme. To test this hypothesis, we asked subjects, in the first experiment, to perform a handle rotation task that demanded little or no precision and so no need to make rapid to-and-fro homing-in movements near the end of the rotation. Half the subjects did not show the end-state comfort effect, in contrast to all previous studies, where all subjects showed the effect. An incidental finding of the first experiment was that handle rotations that ended at or near the end of the range of motion took longer than handle rotations that ended at or near the middle of the range of motion. To test the latter result more * Corresponding author. E-mail: darl2@cac.psu.edu, Fax: + 1 814 863-7002, Tel.: + 1 814 863-1991. i These experiments were conducted while the second author completed an internship with the first author at the University of Massachusetts, Amherst. The studies were described in a thesis submitted by the second author to the University of Leiden in partial satisfaction of the Doctorandus degree. 0001-6918/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. SSDI 0001-6918(95)00062-3