The perceived direction and speed of global motion in Glass pattern sequences

Observers indicated the perceived direction of global motion in sequences of noisy Glass patterns containing real motion signals in directions that conflicted with the orientation of signal dipoles in the Glass patterns. Dipole orientation influenced the perceived direction of motion. Observers also judged the apparent speed of sequences of independent noiseless Glass and Glass Line patterns (dipoles replaced by lines). Speed was high and increased with the length of lines in Glass Line patterns but not with dipole separation in Glass patterns. When real motion signals were added to sequences of noisy Glass patterns they exerted an influence on apparent speed that increased with motion signal strength but was independent of pattern signal strength. The results suggest that pattern exerts a global influence on the computation of motion direction and, possibly, on speed.