Second-order motion perception: space/time separable mechanisms

Microbalanced stimuli are defined as dynamic displays which do not stimulate motion mechanisms that apply standard (Fourier-energy or autocorrelation) motion analysis directly to the visual signal. Because they bypass such first-order mechanisms, microbalanced stimuli are uniquely useful for studying second-order motion perception (motion perception served by mechanisms that require a grossly nonlinear stimulus transformation prior to standard motion analysis). Some stimuli are microbalanced under all pointwise stimulus transformations and therefore are immune to early visual nonlinearities. They are used to disable motion information derived from spatial (temporal) filtering to isolate the temporal (spatial) properties of space/time separable second-order motion mechanisms. The motion of all of the microbalanced stimuli considered can be extracted by band-selective spatial filtering and biphasic temporal filtering, nonzero in DC, followed by a rectifying nonlinearity and standard motion analysis.<>