Motor activation in language processing : effects of handedness, experience, and planning

Field: Psychology (Social Sciences)

Embodied Cognition accounts propose that motor activation contributes to semantic \nrepresentations in action language (Fischer & Zwaan, 2008). However, the nature of this \nactivation remains largely unspecified: in particular, which processes result in relevant \nactivation? Long-term motor experience (e.g., the comprehender’s dominant hand), short-term \nmotor experience (e.g., the hand the comprehender has recently used), and action \nplanning (e.g., the hand the comprehender is planning to use) are all potential candidates. \n \nThis thesis uses a range of psycholinguistic methods (e.g., timed sentence-picture matching, \ntwo-alternative forced-choice sentence-picture matching, spoken sensibility judgements) to \ndistinguish between these possibilities. \n \nA first set of experiments investigated how comprehenders’ handedness affects their \ninterpretation of sentences describing manual actions (e.g., I am slicing the tomato). \nParticipants matched sentences of actions to pictures of that action. The Body-Specificity \nHypothesis (Casasanto, 2009; Willems, Hagoort, & Casasanto, 2010) predicts that right-handed \nand left-handed comprehenders will interpret manual action sentences differently, \naccording to whether they would perform that action with their right or their left hand. \nHowever, we found that comprehenders appear to interpret manual action sentences \naccording to the hand they use to respond to the task, and not the hand they would typically \nuse to perform manual actions. In addition, this effect was stronger for first-person than \nthird-person sentences, implying that the effect of motor activation is moderated by \nlinguistic context. \n \nA second set of experiments used the same paradigm but manipulated at what point \ncomprehenders knew which hand they would use to respond to the sentences: during \nsentence processing, or after sentence processing was complete. We replicated the finding \nthat comprehenders interpret manual action sentences according to their response hand, and \nthat this effect was stronger for first- than for third-person sentences; but only when \ncomprehenders knew their response hand during sentence processing. In both sets of \nexperiments, there was no effect of whether the picture of the action was presented from an \negocentric or allocentric perspective, implying that action sentences are encoded for what \neffector (in this case, hand) will be used in the action, but not necessarily from what \nperspective the action will occur. \n \nA third set of experiments investigated the existence of a causal role of action planning-based \nactivation on sentence processing. Many studies have shown an effect of language \nprocessing on action execution (e.g., Glenberg & Kaschak, 2002; Glenberg et al., 2008), but \na fully embodied theory of language also predicts an effect of motor activation on language \nprocessing. Here, right-handed participants made spoken judgements about sentences while \nplanning an action with their right or left hand that matched or did not match the action \ndescribed in the sentence. An effect of response hand on accuracy was found when the task \nrequired participants to explicitly judge the congruency of sentence and the action they were \npreparing, but not otherwise. These results corroborate recent research suggesting that \nactivation of embodied lexical representations may be goal-driven rather than an automatic \naspect of language processing (Hoedemaker & Gordon, 2013). \n \nOverall, the experiments presented in this thesis suggest a possible role for planning-based \nmotor activation in sentence processing, in line with embodied approaches; however, \nthe results challenge strong accounts of embodiment by suggesting that the effect of \nplanning-based activation is not automatic, and is moderated by linguistic context and task \ndemands.