We compared the head movements accompanying gaze shifts while our subj
ects executed different manual operations, requiring gaze shifts of ab
out 30 degrees. The different tasks yielded different latencies betwee
n gaze shifts and hand movements, and different maximum velocities of
the hand. These changes in eye-hand coordination had a clear effect on
eye-head coordination: the latencies and maximum velocities of head a
nd hand were correlated. The same correlation between movements of the
head and hand was also found within a task. Therefore, the changes in
eye-head coordination are not caused by changes in the strategy of th
e subjects. We conclude that head movements and saccades during gaze s
hifts are not based on the same command: head movements depend both on
the actual saccade and on possible future gaze shifts.