Fig. 3. Kinetics of rotation and translation components during turning. (A) In response to the onset of a visual motion stimulus, i.e. a step in the temporal frequency (TF), stick insects change their locomotor behaviour from a steady straight walk to a steady curve walk. (B–D) The three degrees of freedom of horizontal locomotion were analysed separately and illustrated by their average rate of change per 0.54 s (14 time bins per 7.5 s) among 33 trials from eight animals (square symbols). (B) Angular velocity of yaw rotation (R), (C) speed of sideward translation (Ty) and (D) speed of forward translation (Tx). Values are means ± S.D., indicating the variability among trials. Arrows in the insert show the sign convention. In response to the visual motion stimulus, angular velocity increases with a time constant of 2.4 s. The speed of sideward translation also increases significantly with a time constant of 2.7 s. Forward speed does not change significantly. Steady state velocities during straight and curve walking are indicated by horizontal solid lines in the first and third measurement interval. Exponential curve fits link significantly different steady states.