The history of saccadic suppression is reviewed and the suggested causes of the phenomenon are described. Primary emphasis is placed on "ordinary" saccadic suppression, that is, decreased sensitivity for stimulation received from the outside environment either during or within a few hundred milliseconds of the time of occurrence of a saccade. However, the suppression of afterimages and entopic images is also considered. Some suggestions are made about suppression's role in maintaining a stable visual world (constancy of visual direction) when voluntary saccades occur.

Information-processing time was compared for serial and spatially distributed visual presentations with performance measures that permit the separation of total time into its during-display and post-display components. For all subjects, there was a significant saccadic overhead, that is, less time was required with the serial format, which allowed data access without eye movements. However, the magnitude of the overhead decreased as task complexity increased. All subjects were able to exercise some control over the distribution of total processing time, trading off short during-display times with longer post-display times and vice versa.The purpose of the present research was to measure the "cost" of a saccadic eye movement. Our strategy was to measure information-processing time under two conditions, serial and spatially distributed. The former allowed information access without eye movements and the latter required them. However, all other aspects of the experimental procedures were strictly identical. The serial/spatial processing time difference is operationally defined here as the saccadic overhead.

A vertical slit of light illuminated during horizontal saccadic eye movements appeared as a horizontally extended smear when stimulation was terminated before the saccade ended. However, on trials for which duration of illumination of the slit was extended into the period after the saccade, the smear appeared shorter and dimmer, and a clear image of the slit was seen. With further increases in duration, no smears were seen at the highest luminance of the slit employed, although smears were more than 2 log units above threshold when flashes were brief. This saccadic suppression is discussed in terms of metacontrast, with the accumulated luminance in the period after the saccade primarily responsible for masking the effects of the stimulation received during the movement of the eye.

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The logic of masking experiments and other experiments employing a similar temporal paradigm is considered. Contrary to the usual theoretical assumptions, it is suggested that three classes of neurons could be responding, at least in some cases, to the two stimuli presented in such experiments. The first of these consists of neurons stimulated by the target, and the second consists of neurons stimulated by the mask (or other inducer). Neurons of the third class respond minimally, if at all, to either of these stimuli alone, but are fired by their combined presentation at appropriate temporal intervals. The possibilities for thinking with this additional degree of freedom are illustrated with visual lateral masking. Some specific points considered are the effects the postulated third class of neurons could have on the temporal properites of metacontrast, the possible role of these neurons in producing a strong metacontrast and a weak paracontrast, and the relation they could have to the well-known correlation between apparent movement and masking. It is suggested that some members of the third class could be involved in the sensation of motion. Others, tuned to a broad range of velocities including some very high ones, could be involved in saccadic suppression and visual masking.