[mod. f. Gr. τάχιστο-ς swiftest + -SCOPE.] An instrument by means of which objects may be presented to the eye for a brief measured period, a fraction of a second; one of its principal applications being the measurement of ‘the span of apprehension,’ that is, the amount of detail that can be apprehended by a single act of attention or apperception.
1909. C. S. Myers, Text-bk. Exper. Psychol., 415. The essentials of a good tachistoscope.
