Human Movement Science 25 (2006) 293–309 www.elsevier.com/locate/humov 0167-9457/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.humov.2006.03.005 Distinct mechanisms for planning keypress and reaching responses: A developmental study Jos J. Adam a,¤ , Stijn Parthoens a , Jay Pratt b a Department of Movement Sciences, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands b University of Toronto, Canada Available online 2 May 2006 Abstract This study examined developmental eVects in the ability to use precue information for the plan- ning of keypress and reaching responses. Participants from four age groups (7, 9, 13, and 21 year olds) performed a spatial precuing task either by pressing one of four response keys (keypress task) or by reaching directly toward one of the four target locations on the screen (reaching task). Reaction time data revealed striking age diVerences in the ability to use advance information in the keypress task, not in the reaching task. This dissociation conWrms the hypothesis that distinct and separate mechanisms govern the planning of indirect keypress and direct reaching responses.  2006 Elsevier B.V. All rights reserved. PsycINFO classiWcation: 2330; 2800 Keywords: Motor planning; Motor development; Spatial precuing task; Reaction time; Pointing 1. Introduction Reaction time (RT) methodology is a most eVective research tool in experimental psy- chology (e.g., Luce, 1986). RT is the time that elapses between the onset of the target stimu- lus and the onset of the required response. Often, the response is arbitrary and symbolic, such as a simple keypress response or a verbal yes/no response. While mental chronometry using such symbolic or indirect responses has revealed important insights into the underlying * Corresponding author. Tel.: +31 43 3881389; fax: +31 43 3670972. E-mail address: jos.adam@bw.unimaas.nl (J.J. Adam).