The Psychology of Reaching: Action Selection, Movement Implementation, and Sensorimotor Learning

Abstract

The study of motor planning and learning in humans has undergone a dramatic transformation in the 20 years since this journal's last review of this topic. The behavioral analysis of movement, the foundational approach for psychology, has been complemented by ideas from control theory, computer science, statistics, and, most notably, neuroscience. The result of this interdisciplinary approach has been a focus on the computational level of analysis, leading to the development of mechanistic models at the psychological level to explain how humans plan, execute, and consolidate skilled reaching movements. This review emphasizes new perspectives on action selection and motor planning, research that stands in contrast to the previously dominant representation-based perspective of motor programming, as well as an emerging literature highlighting the convergent operation of multiple processes in sensorimotor learning. Expected final online publication date for the Annual Review of Psychology, Volume 72 is January 5, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Moving outside the lab: The viability of conducting sensorimotor learning studies online

“…This invariance poses a challenge to the standard state-space model of sensorimotor adaptation where the rate and magnitude of learning are dependent on error size (Herzfeld, Vaswani, Marko, & Shadmehr, 2014; Marko, Haith, Harran, & Shadmehr, 2012; Shadmehr et al, 2010; Smith, Ghazizadeh, & Shadmehr, 2006). Thus, the current results add additional evidence pointing to the need for novel perspectives of adaptation, ones that do not assume adaptation to be sensitive to error size, but instead constrained by the limits of sensorimotor plasticity (Kim et al, 2018) or sensory biases (Heald, Lengyel, & Wolpert, 2020; Jonathan S. Tsay, Kim, et al, 2020).…”

“…If the mismatch is small, this change will emerge in a gradual manner over trials and occurs outside the participant’s awareness, a phenomenon known as implicit sensorimotor adaptation. If the mismatch is large, this adaptive learning process may also be accompanied by more explicit adjustments in aiming (Kim, Avraham, & Ivry, 2020; McDougle, Ivry, & Taylor, 2016; Shadmehr, Smith, & Krakauer, 2010).…”

Reexposure to a sensorimotor perturbation produces opposite effects on explicit and implicit learning processes

“…Yet, the behavioral changes observed during sensorimotor learning do not arise solely from explicit strategy use. The behavioral change in such tasks is also driven by implicit adaptation, the adjustment in the sensorimotor map that occurs outside awareness and volitional control [13]. Indeed, in many contexts, especially those involving small perturbations, most of the learning is implicit [12,14,15].…”

A conversion from slow to fast memory in response to passive motion

“…But in a more general sense, prediction errors do not necessarily require movement. For example, in classical conditioning, these errors are driven directly by unexpected sensory stimuli (Ohmae & Medina, 2015; Kim et al, 2020; Ito, 2007; Sears & Steinmetz, 1991; Rasmussen et al, 2008). Here, we wondered if passive movements could generate prediction errors in a similar manner, and if consistent exposure to these errors might increase sensitivity to error during active motor learning.…”