The development of walking: new findings and old assumptions.

I have argued that a behavioral-cognitive perspective may shed light on some aspects of motor development generally, and unaided walking, specifically. Individual components of walking-stepping, standing, and placing, for example-are present at birth and can be maintained with practice. Moreover, consistent use can produce an earlier onset of unaided walking. Nonetheless, independent erect locomotion rarely occurs before about 9 months in most societies, implying that there is a maturational constraint. Independent research on changes in the quality of object use imply that the maturational limitation may be cognitive, in part. Changes in motor development-both the onset of unaided walking and the emergence of functional use-may be dictated by an underlying change in information processing ability. It is hypothesized that the infant's capacity to generate ideas or access different associations from memory rapidly may define the nature of this change. Improved access to memory may permit the necessary integrative capacity for balance and coordination to occur, thereby permitting unaided walking to develop. Weiss and Zelazo found that the capacity to perform two distinct actions in rapid succession in an independent environment-water-also appears to emerge from about 9 through 12 months. Not only may a cognitive change influence motor development, but mental and motor ability may develop asynchronously in some instances-a particularly important implication for developmental assessment. Procedures to distinguish information processing ability independent of gross and fine motor measures and productive language can lead to treatment that will reduce delays on conventional tests and contribute to the validity of this argument.