Dr David McGrath

Spine Physician

MB BS (Hons) FAFOM, RACP, FAFMM
Master of Pain Medicine

Movement Space

Every environment requires a set of movements in order to survive (a+c). Importantly, every person has an available set of movements which they can utilise in the environment (a+b). The two sets are not always 100% compatable. The goodness of fit, is a indicator of the quality of the niche.

Examining the maths a little more closely.

Movement Set Rquirements	Required Movements	Non Required Movements
Available Set	a (match)	b (irrelevant)
Non Available Set	c (deficiency)	d (reserve)

Cell "a" is the available set of movements needed for a domain (match)
Cell "b" is the available but redundant set of movements needed for a domain (irrelevant)
Cell "c" is the unavailable set of movements needed for a domain (deficiency)
Cell "d" is the unavailable set of movements not needed for a domain (reserve)

We could define
1. The potential error rate as 1-a/(a+b)
2. The knowledge gap as 1-a/(a+c)

Optimally, we would like b=0 and c=0, leading to 0% error and 0% knowledge gap.
Observing any skilled person, we can notice that they appear, to make very few errors and have sufficient knowledge for their domain of skill. In terms of the contingency table, deficiencies are low, with few irrelevencies.

We can make some more observations. Knowledge, in terms of efficient action, cannot be defined as "stuff" we learn. The knowledge base (a+b) is insufficient as a descriptor of knowledge gap and error rate.
If a person knows how to play tennis and badmington, but cannot seperate out the stroke skills, both tennis and badmington are likely to suffer. In addition, the combined knowledge, cannot make up the shortfall of a missing stroke (eg volley)

Further Related Reading: Movement Skills