Reproducible eye movements regardless of time reversal. A, Cross-correlations of eye positions over time for the two forward presentations of the silent films. Red curve, Vertical eye position. Blue curve, Horizontal eye position. The correlation was computed at different lags (0.2 s intervals); the peak at lag 0 indicates a reproducible sequence of eye positions in the two presentations, that was time-locked to the movies. Error bars indicate SEM across observers. B, Cross-correlations for the two backward presentations. C, Cross-correlations for the reversed-backward and forward presentations. The high correlations indicate that the sequence of eye positions was similar (but reversed in order) during the forward and backward viewings. Correlation coefficients at zero lag corresponding to forward:forward, backward:backward, and forward:reversed-backward were not statistically distinguishable from one another C_F1:F2:C_B1:B2 horizontal eye position, p = 0.54; C_F1:F2:C_B1:B2 vertical eye position, p = 0.43; C_F1:F2:C_rB:F horizontal eye position, p = 0.22; C_F1:F2:C_rB:F vertical eye position. p = 0.3). D, Cross-correlations for the backward (not flipped) and forward presentations.