Barriers to understanding natural variability.
By: Bruce J. West
In: Journal of Evaluation in Clinical Practice
Date: 11 March 2010
- Most decision making revolves around pattern recognition [prediction].
- Data => information => patterns => knowledge, models.
- Comparing patterns in the brain with patterns in the environment.
- Humans make decisions based on the compatibility of these patterns.
- Old approach: homeostasis = the ideal (average) equilibrium physiological configuration for survival.
- Human body evolved to optimize for survival.
- Resists change.
- Identify best range of operation for cardiovascular, respiratory and other physiological systems.
- Most important measurement is the average value, assuming limited variability.
- Dysfunction is a function of deviation outside the normal distribution.
- Associated with a mechanical world view.
- View that dominates physical, social and life sciences.
- Mechanical processes have a “best”, or average, value.
- Deviations from the average are errors.
- Small errors are more common than large ones.
- Gaussian distribution (thin tails).
- Individual behavior varies, population characteristics are stable and predictable.
- Order, regularity emerges out of disorder.
- Average value characterizes the phenomenon of interest.
- However, much of the world does not work this way.
- Non-linear dynamics: small changes can have large effects.
- Complex networks; unstable, unpredictable processes.
- Small number of elements represent disproportionate share of outcomes (eg, wealth).
- Limited ability to control or predict.
- Failure of average to capture the properties of a phenomenon.
- Pareto distribution (power laws, fat tails).
- New approach: homeostasis = variability necessary for adaptation.
- Body has to adapt to rapid, short-term, complex changes in the environment.
- Accommodate change, instead of resisting it.
- Patterns of variability, not average value, are indicators of health.
- Too much = no good.
- Too little = no good.
- A decline in variability signals deterioration in health, ability to adapt.
- Complex networks: variability, rate of change matter.
- Previously, control of the world focused on control of man-made machines.
- Similar mechanistic approach to non-linear networks and processes not effective.
- Different measures: variability instead of average.
- Process matters: Rate of change versus range of outcomes.