Figure 1: The percentage error in direction judgements is plotted as a function of stimulus displacement for each of four subjects. Displacement is expressed in terms of the wavelength (lambda) of the carrier of the Gabor micropatterns. The lefthand plots (A-C) show the results obtained using sparse stimuli (36 micropatterns), the righthand plots (D-F) show the results for dense stimuli (66 micropatterns). The sparse stimuli were made up of 6 micropatterns per row, giving a mean centre-to-centre spacing of 4.5l between micropatterns. The dense stimuli contained 11 micropatterns per row at a spacing of 2.25l. The top plots (A, D) show data from Condition 1, in which motion is defined by the displacement of Gabor micropatterns. The middle plots (B, E) show data from Condition 2, in which motion is defined by the displacement of Gaussian micropatterns. The bottom plots (C, F) show data from Condition 3, in which the envelopes of Gabor micropatterns are displaced while their carriers remain static.