Attentional asymmetry in rhythmic interlimb coordination induces an asymmetry in relative phase dynamics, allegedly reflecting an asymmetry in coupling strength. However, relative phase asymmetries may also be engendered by an attention-induced difference between the amplitudes (and hence the preferred frequencies) of the limb movements. The authors conducted 3 experiments to dissociate those (not mutually exclusive) potential effects. Controlled manipulations of amplitude disparity and attentional focus, both alone and combined, revealed that variations in amplitude disparity had the expected effects, but produced evidence against the currently prevailing interpretation that attentional asymmetry affects the relative phase dynamics through an asymmetry in coupling strength. Implications of these findings are discussed vis-à-vis recent empirical findings and extant dynamical models.