Fig. 4.

Temporal dynamics of motion perception. (A) A field of moving bars, moving ±45° relative to the their orientation or perpendicular to it, was displayed within a circular aperture, represented by a dashed circle (only probes within the aperture were active). (B) The perceived direction of the bars changed with time; the dashed line represents their veridical direction of movement. The perceived direction is represented as the angular difference between the perceived direction and the direction orthogonal to the bars' orientation. The bias was most prominent for the short duration stimuli but was still present after 600 ms of stimulation. (C) The perceived direction of the barber pole (aspect ratio = 2) changed with time. The gray bar shows the perceived direction when the stimulus duration was 1 s (same data as shown in Fig. 3). The perceived direction is expressed relative to the direction orthogonal to the grating's orientation. The aperture effect was weaker for short-duration stimuli and plateaued after ≈400 ms. Note that different subjects participated in the main barber pole experiment (the results of which are shown in Fig. 3 and as the 1,000-ms bar in C here) and in the experiment investigating the temporal dynamics of the barber pole effect (the results of which are shown as the black bars in C), which may explain why the steady-state bias is slightly smaller in the former than in the latter.