The multiple process model of goal-directed aiming/reaching: insights on limb control from various special populations

Abstract

Several years ago, our research group forwarded a model of goal-directed reaching and aiming that describes the processes involved in the optimization of speed, accuracy, and energy expenditure . One of the main features of the model is the distinction between early impulse control, which is based on a comparison of expected to perceived sensory consequences, and late limb-target control that involves a spatial comparison of limb and target position. Our model also emphasizes the importance of strategic behaviors that limit the opportunity for worst-case or inefficient outcomes. In the 2010 paper, we included a section on how our model can be used to understand atypical aiming/reaching movements in a number of special populations. In light of a recent empirical and theoretical update of our model (Elliott et al. 2017), here we consider contemporary motor control work involving typical aging, Down syndrome, autism spectrum disorder, and tetraplegia with tendon transfer surgery. We outline how atypical limb control can be viewed within the context of the multiple process model of goal-directed reaching and aiming, and discuss the underlying perceptual-motor impairment that results in the adaptive solution developed by the specific group.

Developmental differences in the prospective organisation of goal‐directed movement between children with autism and typically developing children: A smart tablet serious game study

“…In this way, kinematic differences in autism can be seen as an adaptive developmental response to optimise movement to achieve goals in the presence of intrinsic neuromotor constraints. This is supported by recent empirical work reviewed by Elliott and colleagues ( 2020 ) showing that motor learning in autistic individuals leads to different kinematic patterns (such as increased spatial variability). Importantly, motor control and learning nevertheless appear intact as autistic individuals successfully solved the motor task.…”

“…Deficit versus strategic optimisation. Our study adds to the debate on whether kinematic differences indicate simply a disturbance in the sensorimotor system in autism, or a strategic optimisation due to underlying differences in the neuromotor system (Elliott et al, 2020;Latash & Anton, 1996). In previous studies, it was difficult to argue for whether atypical kinematic differences relate to the former or latter in older individuals whose motor skills are already well-developed.…”

“…Notably, not all movement differences are deficits per se. Individuals optimise movement kinematics in reaction to external task constraints that affect the efficiency and accuracy of their movements in relation to a goal (Elliott et al., 2020 )—a fundamental principle of prospective action organisation (Lee, 2009 ). While it has been suggested that there may be some form of neuromotor disruption in autism, such as greater motor noise or imprecise muscular timing, these can be understood as internal constraints on goal achievement.…”

Binocular Viewing Facilitates Size Constancy for Grasping and Manual Estimation

“…Adopting an appropriate safety margin for task performance is a key feature of human behaviour, which may be learned based on experience [ 49 ]. Studies show that participants adopt a larger safety margin when faced with increased sensory uncertainty such as reduced cues [ 51 , 52 , 68 ], and/or higher motor variability which increases when movements are performed faster [ 50 , 53 , 69 ]. Here we propose that the safety margin for reaching and grasping can be quantified as the intercept from the regression relating grip aperture and object size, and peak velocity and object distance, respectively.…”

The role of binocular vision in the control and development of visually guided upper limb movements

“…The paper begins with a brief summary of binocular processing in typical and atypical development. Next, the contribution of binocular vision to upper limb movement control is examined using the multiple processes model of limb control [12][13][14]. This approach reveals that vergence and stereopsis provide distinct advantages for optimal sensorimotor control and the development of manual dexterity.…”