Figure 2.

(a) Three rows (baselines) of a motion lattice. The solid and open circles stand for dots that appear in frames f₁ and f₂, respectively. The three spatial parameters of motion lattices are: |b|, the distance between adjacent dots in a baseline; |m₁|, the shortest distance between successive dots; and θ₁, the acute angle between the orientations b and m₁. The acute angle between b and m₂ is θ₂. S is the second (after b) shortest distance within a frame. To minimize edge effects, we modulated the luminance of lattice dots [radius = 0.3 degrees of visual angle (dva)] according to a Gaussian distribution (σ = 1.5 dva). We held m₁ (= 0.9 dva) constant. (b) Time line of each trial. We kept the total duration of each presentation at 1.76 s to prevent the percept of oscillatory motion, which sometimes is seen with longer presentations. (c and d) Two successive frames of a motion lattice captured from the computer screen (not to scale). (e) A response screen with three response options. (Labels were not presented in the display.)