NONLINEARITIES OF HUMAN OCULOMOTOR SYSTEM . TIME DELAYS

Measurements of the gain of the human eye movement control system in two-dimensional tracking tasks show that the system is non-linear in the sense that it is not possible to predict the response to one class of target motion by linear combination of the responses to other classes of stimuli. It is therefore not valid to represent the system by a linear transfer function and hence a minimum phase lag cannot be calculated. There is thus no theoretical datum with which to compare the actual phase lags of the visual axes in tracking tasks and hence no evidence for a predictor mechanism. The lags of the visual axes can be satisfactorily explained in terms of simple delays which depend on the class of target motion. © 1969.