Figure 1. Incidence of stepping.

The incidence of obtaining sustained stepping (4 or more alternating steps) on the treadmill for 2 groups of infants: 58 who had no systematic practice stepping (A) and 19 who practiced each day (B). Practice resulted in a dramatic increase in the chance of obtaining stepping. The asterisk in B indicates no data were collected for those age groups. The number of infants in each group is shown in Table 1.