Thursday, October 6, 2011

Beyond Physical Milestones, Part VI: Constraints Theory

         The constraints model directly addresses Bernstein’s problem (defined in the introduction) in that it looks at how to limit the infinite degrees of freedom of human movement.  In 1986, Karl Newell, a researcher at Penn State, proposed that three types of constraints limit the degrees of freedom- organismic, task, and the environment.  From infancy, then, movement is dictated by these constraints.
            Now for the specifics of each type of constraint.  Organismic constraints are those that the individual possesses and are divided into two categories- structural and functional.  Structural constraints, as the name implies, describe constraints from the individual’s body structures; height, weight, vision (especially important for infants as they do not gain binocular vision until about 5 months, which limits their perception), or a broken wrist, for example.  These are typically slower to change.  On the other hand, functional constraints are related to specific functions and are much more time dependent.  Examples include attention, memory, self-esteem, and fear.  Environmental constraints are outside of the individual and include gravity, temperature, social pressure, and lack of teaching.  Task constraints are divided into three parts- task goal (reach the toy hanging from my car seat), rules (staying within boundaries during sports games), and equipment (the safety gate that keeps me out of Daddy’s man cave.)
            To demonstrate his theory, Newell and his fellow researchers gave four different sized blocks to infants between 4 and 8 months.  Although, given the individual has 10 fingers, there are 1,023 different ways to picks up the blocks (so far, I’m on 117), the infants only used five.  This was most likely due to the size of the objects in comparison to the infants’ hands. 
            As in the dynamic systems model, constraints do not act alone.  An infant faces countless and ever-changing constraints as he develops.  According to the constraints model, specific movements and development milestones are his resulting reactions to these constraints.


Getchell, N. & Gagen, L. (2006). Adapting activities for all children: Considering constraints can make planning simple and effective. Palaestra. Retrieved from
Piek, J. (2006). Infant motor development, volume 10. USA: Sheridan Books.
Savelsbergh, G., Davids, K., van der Kamp, J., & Bennett, S. (2003). Development of movement co-ordination in children: applications in the field of ergonomics, health sciences, and sport.  London: Routledge.

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