Why motor imagery is not really motoric: towards a re-conceptualization in terms of effect-based action control

Psychological Research https://doi.org/10.1007/s00426-022-01773-w RESEARCH Why motor imagery is not really motoric: towards a re‑conceptualization in terms of effect‑based action control Patric Bach1 · Cornelia Frank2 · Wilfried Kunde3 Received: 24 October 2021 / Accepted: 11 November 2022 © The Author(s) 2022 Abstract Overt and imagined action seem inextricably linked. Both have similar timing, activate shared brain circuits, and motor imagery influences overt action and vice versa. Motor imagery is, therefore, often assumed to recruit the same motor processes that govern action execution, and which allow one to play through or simulate actions offline. Here, we advance a very different conceptualization. Accordingly, the links between imagery and overt action do not arise because action imagery is intrinsically motoric, but because action planning is intrinsically imaginistic and occurs in terms of the perceptual effects one want to achieve. Seen like this, the term ‘motor imagery’ is a misnomer of what is more appropriately portrayed as ‘effect imagery’. In this article, we review the long-standing arguments for effect-based accounts of action, which are often ignored in motor imagery research. We show that such views provide a straightforward account of motor imagery. We review the evidence for imagery-execution overlaps through this new lens and argue that they indeed emerge because every action we execute is planned, initiated and controlled through an imagery-like process. We highlight findings that this new view can now explain and point out open questions. Introduction Overt and imagined action seems inextricably linked. Before undertaking a difficult motor task, people often experience themselves imagining what they intend to do, and the form this imagination takes (e.g., imagining intended outcomes or motor behaviors) affects task success and subsequent learning (e.g., Land et al., 2014; Woolfolk et al., 1985a, 1985b). Sometimes, people even imagine behaviors they will execute at a much later time and in a different environment, for example, when they mentally play through the actions of their sport from the privacy of their home. Again, this form of motor imagery—sometimes termed mental practice, mental training or motor imagery training (Schack et al., 2014; for definitions and conceptualizations, see Morris * Patric Bach 1 School of Psychology, University of Aberdeen, William Guild Building, Kings College, Aberdeen, UK 2 Department of Sports and Movement Science, School of Educational and Cultural Studies, Osnabrück University, Osnabrück, Germany 3 Department of Psychology, Julius-Maximilians-Universität Würzburg, Röntgenring 11, Würzburg, Germany et al., 2005)—affects later performance (for meta-analysis, Driskell et al., 1994; Simonsmeier et al., 2021; Toth et al., 2020) and is recommended by most professional coaches (Mayer & Hermann, 2019). Purely mental practice can even increase measured muscle strength, from simple finger contractions to leg pressing and triceps extension, albeit not to the same extent as physical practice (Yue & Cole, 1992; for recent replications and review, see Paravlik et al., 2018; Reiser et al., 2011; Smith et al., 2003). Studies from experimental psychology and cognitive neuroscience support this coupling of overt and imagined action. There are tight correspondences between the timing of imagined and overt actions (Decety et al., 1989; Wohlschläger & Wohlschläger, 1998; for a critical review, see Guillot & Collet, 2005), between the activated brain structures in parietal and premotor cortices (for reviews, see Lotze & Halsband, 2006; Hétu et al., 2013; O’Shea & Moran, 2017), and between the lawful regularities that govern the kinematics of both overt and imagined action (e.g., Fitts’ law, Decety & Jeannerod, 1995; two-thirds power law, Karklinsky & Flash, 2015; Papaxanthis et al., 2012). Moreover, several studies show that motor imagery can engender (sub-threshold) activation in the muscles used in the imagined behavior (Guillot et al., 2007, 2010; Jacobson, 1931, 1932; Lutz, 2003; Munzert & Krüger, 2018; Shaw, 13 Vol.:(0123456789) Psychological Research 1938), and, conversely, that executing motor actions makes imagining the same actions easier and imagining different actions harder (e.g., Wohlschläger, 1996, 2001; Callow et al., 2006; Guillot et al., 2013; for a broader review of the effects of such “dynamic motor imagery”, see Guillot, under review). The link from imagined to overt behavior is so strong that it provides the basis for several (stage) magical phenomena. In Chevreul’s pendulum and the Ouija board, for example, seemingly supernatural motions happen simply because participants’ imagined motions are, unbeknownst to them, translated into subliminal hand and finger movements that are made visible by the devices (Cantergi et al., 2021; Chevreul, 1833; Easton & Shor, 1975, 1976, 1977; Wegner et al., 1998). A standard explanation for these findings is that imagery of action is an intrinsically motoric process. This view assumes that motor imagery, in a form of neural re-use (e.g., Anderson, 2010), draws upon the same neuronal networks and cognitive processes that underlie action execution itself (Jeannerod, 1994; Jeannerod & Decety, 1995). As a potential mechanism, it has been proposed that the brain predicts—via forward models—the sensory consequences that each of its motor commands will produce, so that it can anticipate the visual, tactile, and proprioceptive sensations that will soon be registered (e.g., Miall & Wolpert, 1996; Sperry, 1950). During overt action, such predictions may allow the actor to filter out predicted sensations (e.g., Reichenbach et al., 2014) or to correct for movement errors before they happen (e.g., Desmurget & Grafton, 2000; Shadmehr et al., 2010). During imagery, the same forward models could be used offline, triggered perhaps by sub-threshold motor commands, and allow one to mentally play through how different actions will unfold, without the signals ever reaching the muscles (e.g., Jeannerod, 1994; Jeannerod & Decety, 1995; Kilteni et al., 2018). In these proposals, motor imagery is often described as “neural simulation of action” (e.g., Jeannerod, 2001), “covert execution” (e.g., Scheil et al., 2020), and imagined actions are taken as “real actions, except for the fact that they are not executed” (Jeannerod, 2001, p. 103). In essence, these accounts hold that people can imagine their actions because the motoric structures of the brain can, in some form, pretend that the imagined actions are currently executed, and project their perceptual consequences into the imagination, so that one can watch them unfold in front of one’s mind’s eye. Imagination, therefore, has the same timing, is governed by the same regularities, and activates largely overlapping brain structures as overt action. A different view on motor imagery The previous section describes the “standard” (...truncated)