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Exp Brain Res (2007) 182:549558 DOI 10.1007/s00221-007-1013-1
RESEARCH ARTICLE
Methodological problems undermine tests of the ideo-motor conjecture
Erik Jansson Andrew D. Wilson
Justin H. G. Williams Mark Mon-Williams
Received: 20 December 2006 / Accepted: 29 May 2007 / Published online: 26 June 2007 Springer-Verlag 2007
Abstract Recent behavioural research has investigated whether viewing someone perform an action results in activation of that action by the observer. Postulated empirical support for this ideo-motor (IM) conjecture typically rests upon two types of experimental paradigm (reaction time and movement tracking tasks). These paradigms purport to show movement facilitation when compatible movements are observed and vice versa, but only for biological stimuli. Unfortunately, these paradigms often contain confounding (and unavoidable) generic stimulusresponse compatibility eVects that are not restricted to observed human movement. The current study demonstrates in three experiments that equivalent compatibility eVects can be produced by non-biological stimuli. These results suggest that existing empirical paradigms may not, and perhaps cannot, support the IM-conjecture.
Keywords Ideo-motor theory
Stimulusresponse compatibility
Introduction
A large number of recent papers (e.g. Iacoboni et al. 2001; Brass et al. 2001; Kilner et al. 2003; Brass and Heyes 2005) have been based on a conjecture that was Wrst proposed in
the middle of the nineteenth century by William James (1890); see Stock and Stock (2004) for a review. This conjecture, commonly referred to as Ideo-Motor theory or the Ideo-Motor hypothesis (henceforth, IM conjecture), states every representation of a movement awakens in some degree the actual movement which is its object; and awakens it in a maximum degree whenever it is not kept from so doing by an antagonistic representation present simultaneously to the mind (James 1890, p. 1134).
It can be seen that the IM conjecture has three parts. The Wrst is straightforward: (1) a relationship exists between the representation of an action and the resulting movement trajectory. The conjecture then proposes a speciWc form to the relationship: (2) movements are (completely) activated through imagining an actions eVects (including observing a biological agent perform the action, preparing an action or in any other way representing the action); (3) such a represented action must be inhibited or else implemented. The Wrst component of the conjecture is consistent with modern computational models of motor learning (e.g. Wolpert...