Variation and selection in the development of perception and action

Human behavior is much more variable than traditionally assumed, and it is precisely because of this variability that many new responses are introduced into the behavioral repertoire. As individuals select and explore new behaviors, a distribution of intrinsic and/or extrinsic values drives each person to store and repeat those responses that are optimally successful. This principle of opportunistic selection is illustrated by examples from the development of interlimb coordination and postural control. It is concluded that variation serves multiple functions in organizing human behavior depending on the level of analysis and whether the variability is structured or completely random.