Figure 7.

Assessing the performance of models of motion integration. The relative perceived directions of additional type 2 plaids (0° corresponds to the veridical direction), measured in human psychophysical experiments. Components were systematically varied in a factorial design: component 1 was scanned at −10, −20, or −30° and component 2 was scanned at −60, −65, −70, −75, −80, or −85° relative to the direction of the plaid pattern. Again, the full Vector Average model predicts the performance of human subjects. The psychophysical data (circles with error bars) are shown with the predictions (dotted traces) of (A) the full Vector Average model, (B) the Vector Average model without the terminator term, (C) the Vector Average model without speed weighting, and (D) the contrast normalization model (Busse et al., 2009), which has been shown to effectively predict the responses of V1 neurons to superimposed gratings. E. The Vector Average (VA) model predicts that, as the relative amplitudes of the component gratings are varied in small increments, the perceived direction will shift gradually. As predicted by the model, the distribution shifted gradually from component to pattern motion. Mean perceived direction measured from seven subjects (blue trace) along with the predictions from the full Vector Average model (red dashed trace) and the Vector Average model without the terminator term (green dashed trace). The full Vector Average model prediction matches the psychophysical data almost perfectly. F. In the full Vector Average model, W_t is relatively constant (around 0.35) across the four protocols (identified in the legend; protocol 4 refers to the psychophysical data shown in panels A–D). F. The Vector Average model accounts for most of the variance in perceived direction across the four protocols (identified in the legend of panel E).