Visual perceptive simultaneity and masking of letters successively presented

Two sets of letters S₁ and S₂ when presented successively are perceived as simultaneous if the total duration of time from the beginning of S₁ to the end of S₂ is kert constant, whatever the duration of S₁, S₂, or the interval. The same law applies in the case of dots arranged to form geometrical figures. On the other hand, the phenomena of meta-contrast with letters are modified when the relative duration of S₁, S₂, and the interval vary. Thus perceptive integration and masking depend upon different processes.