Means were calculated as the average smooth eye velocity in the direction of the stimulus, over the 500 msec time the stimulus was present, after excision of saccades. Means are shown for both monkeys, two target velocities, and the full range of values of Δt. For those values of Δt that evoked statistically significant increases in pursuit eye acceleration, parentheses show the percentage of the increase in estimated speed (calculated using the static version of the opponent vector-average) that could be accounted for by the change in smooth eye velocity from when Δt was 4 msec. Negative percentages indicate that the artifact introduced by smooth eye movements would actually produce a decrease in estimated speed.