Orthographic regularity, lexical status, and letter-identification acuity.

Hershenson reported in 1980 that accuracy for identifying letters from seven-letter strings was not affected by the orthographic regularity or the lexical status of the strings when the letter to be reported was indicated by a vertical bar marker that appeared simultaneously with the string or immediately after it. Since the initial visual representation begins to fade soon after stimulus offset and lasts for about 250 msec., stimulus structure may affect the extraction and storage processes necessary to produce a correct response if the indicator is delayed. Two experiments explored this region by sampling seven retinal locations within the central 2.6 degrees of the visual field. The indicator was delayed for 100, 200, and 300 msec. in Exp. 1 and 0, 25, 50, and 75 msec. in Exp. 2. Stimulus structure did not affect accuracy of identification when subjects were equally familiar with the letter strings (memorization group) but had a strong effect for the group instructed to guess (forced-guess group). The group unfamiliar with the strings but instructed not to guess (no-guess group) showed effects of stimulus structure only at delays of the indicator longer than 100 msec. These data support a model of visual processing that includes an initial representation unaffected by orthographic regularity or lexical status, variables that determine the availability of information only when it must be retained before it is used.