Motor Control Theory Dynamic & Ecological Approaches (Large parts adapted from Wallace, 1993)

Asking the right question/questions How do we move the way we do? Seeks one solution A causal influence Tends to emphasize neural solutions Tends to lead to “hypothetical constructs” to achieve solutions where neural solutions are not known Tends to shape one’s thinking of control as a hierarchy

Asking the right question/questions Why do we move the way we do? A different focus Tends to make us look at all possible influences on the shape of movement Does not seek one solution, but accepts many simultaneously Tends to shape one’s thinking of control as a heterarchy This is the way we’ll be approaching the problem

A heterarchical theory of control Or theories... Complex systems theory Dynamic pattern perspective & synergetics Ecological psychology All have in common the tendency to ask why rather than how The study of relationships among things, rather than the things themselves Leads to the study of...

A heterarchical theory of control Constraints... Things which limit our range of movements – thus “shaping” them...and affordances Things which permit (or even suggest) certain methods of movement or interaction with an object

A heterarchical theory of control Surface type Lighting Visual flow Speed/accuracy requirements Number of tasks standing seated moving Sensory loss Cognition Flexibility Strength/power Cardiovascular Environmental Constraints Individual Capabilities Task Demands 3 categories of constraint (+ examples) Motor abilities Environmental stability From Newell (1986)

A heterarchical theory of control Processes in coordination dynamics Dynamics of CNS (neural level) Dynamics of action system (effector level) Dynamics of environment (environmental level) ConnectionismAction system theory Laws of perceiving and acting (ecological psychology) Coordination dynamics From Schmidt & Fitzpatrick (1993)

An example (physical world) Systems far from equilibrium There are no instructions determining the pattern of behavior – just elements of the system interacting But this isn’t very complex Equilibrium Closed system Punch hole in container Open system Far from equilibrium Listen to this first……then this…

A more complex example The Benard instability (Prigogine & Stengers, 1984) Again, the system self-organizes to these patterns Heat is a control parameter (this forces the system to change its organization) (hexagon: from temp gradient + descent of cool molecules via gravity) heat A pan of about 1cm depth of oil More heat random hexagonalturbulence

A more complex example The Benard instability (Prigogine & Stengers, 1984) Note that each pattern does change, but it resists change also – a property known as stability Stability and loss of stability are central to dynamic pattern theory heat More heat random hexagonalturbulent A pan of about 1cm depth of oil

Pause, consider, then move on… Getting too big – have to break down into multiple slide sets