...increased sensory motor stimulation!
The "small foot" or the "short foot" is a commonly used term in the rehabilitation industry and is of paramount importance for facilitating upright whole body stability. With the vast amount of receptors located at the sole of the foot, the small foot helps to increase afferent input thereby sending important information higher up the system to aid in motor system regulation.
Here is an ideal progression for the facilitating the short foot.
For more information on the short/small foot, check out Patrick Ward's blog, Chapter 22 of Liebenson's Rehabilitation of the Spine or Page, Frank, & Lardner's Assessment and Treatment of Muscle Imbalance: The Janda Approach (click on Educational Resources above).