We measured the gain and phase of vertical vergence in response to dis
junctive vertical oscillations of dichoptic textured displays. The tex
ture elements were m-scaled to equate visibility over the area of the
display and were aperiodic and varied in shape so as to avoid spurious
binocular matches. The display subtended 65 degrees and oscillated th
rough peak-to-peak amplitudes from 18 are min to 4 degrees at frequenc
ies from 0.05 to 2 Hz - larger ranges than used in previous investigat
ions. The gain of vergence was near 1 when the stimulus oscillated at
18 are min at a frequency of 0.1 Hz or less. As the amplitude of stimu
lus oscillation increased from 18 are min to 4 degrees, vergence gain
decreased at all frequencies, which is evidence of a nonlinearity. Gai
n declined with increasing stimulus frequency but was still about 0.5
at 2 Hz for an amplitude of 18 are min. Phase lag increased from less
than 10 degrees at a stimulus frequency of 0.05 Hz to between 100 degr
ees and 145 degrees at 2 Hz. Overall, the dynamics of vertical vergenc
e resemble the dynamics of horizontal vergence and cyclovergence.