The purpose of this study was to examine if there is any developmental chan
ge in the coupling between visual information and trunk sway in infants as
they acquire the sitting position. Twenty-four infants distributed in four
groups (6-, 7-, 8-, and 9-month-old) were sat inside a moving room that osc
illated back and forward at frequencies of 0.2 and 0.5 Hz. The results reve
aled that trunk sway matched to the moving room at both frequencies but did
not differ among the four age groups. Coherence and gain revealed that the
coupling was weaker at 0.2 than at 0.5 Hz. Relative phase showed that at 0
.2 Hz, infants were swaying with no lag but at 0.5 Hz they were tagging the
room. These results showed that the coupling between visual information an
d trunk sway in infants varies with the visual stimulus but does not change
as infants acquire the sitting position. (C) 2000 Elsevier Science Inc. Al
l rights reserved.