The television show 60 Minutes
presented a story about how patients can today control robotic arm/limb prostheses. In the episode (click here
for more information), the interviewer was surprised to learn that a soldier who had tragically lost his lower arm in combat could, in just a few trials, control the grasping motions of a robotic hand. This prosthesis was connected to electrodes attached to the muscles of the remaining part of the soldier's upper arm. The interviewer asked the soldier how he knew which muscles to activate in order to enact the robot's action. The soldier replied to the effect that he had no idea regarding which muscles to activate, nor what the muscles were actually doing. Rather, the soldier claimed that, to enact the action on the part of the robotic arm, all he had to do was imagine the grasping action. This image, what Harleß in the nineteenth-century called in German the Effektbild
(in English, "the picture or image of the effect") was somehow translated (unconsciously) into the kind of muscular activation that would normally result in a grasping action.
Is this how people generally guide and perceive their own actions? According to William James', the father of American psychology and popularizer of this kind of ideomotor theory, the answer is a resounding yes. Ideomotor theory states that action guidance, and action knowledge, are limited to perceptual-like representations of action outcomes (e.g., the ‘image' of one's finger flexing), with the
motor programs/events actually responsible for enacting the actions being unconscious (click here
from more). From this standpoint, conscious contents regarding an ongoing action are primarily of the perceptual consequences of that action. In James' own words, "In perfectly simple voluntary acts there is nothing else in the mind but the kinesthetic idea…of what the act is to be” (Principles of Psychology,
p. 771). Today, ideomotor theory may prove to be helpful not only for understanding the control of everyday behavior but also for illuminating how patients can benefit from the specific technology mentioned on 60 Minutes
and from the more general forms of brain computer interfaces (BCIs), which must be intuitive and easy to use (click here
for more information about brain computer interfaces).
To learn more about Ezequiel Morsella's research and books (e.g., Oxford Handbook of Human Action), please visit his lab's website, the Action and Consciousness Lab.