Paracontrast

An apparatus for the demonstration of the phenomena of the time relations of visual stimuli, and of meta- and paracontrast.

Masking between non-overlapping stimuli is termed paracontrast when the mask precedes the target, and metacontrast then the mask follows the target (equivalent to forward and backward masking between overlapping stimuli).

A particular type of forward masking, in which the target and mask are spatially nonoverlapping, as in metacontrast, is called paracontrast masking.