The psychometric function of single-letter identification is typically described as a function of stimulus intensity. However, the effect of stimulus exposure duration on letter identification remains poorly described. This is surprising because the effect of exposure duration has played a central role in modeling performance in whole and partial…

In 6 experiments, the authors investigated the form of serial position functions for identification of letters, digits, and symbols presented in strings. The results replicated findings obtained with the target search paradigm, showing an interaction between the effects of serial position and type of stimulus, with symbols generating a distinct…

A sparse mask that persists beyond the duration of a target can reduce its visibility, a phenomenon called "object substitution masking". Y. Jiang and M. M. Chun (2001a) found an asymmetric pattern of substitution masking such that a mask on the peripheral side of the target caused stronger substitution masking than on the central side.…

In two experiments, a probe technique required subjects to respond when the digit 7 appeared in one of five-letter positions in words or nonwords, inserted at the onset and 500 msec after letter and word processing. The focus of attention given to a letter has a smaller spatial extent. (Author/CM)

Reaction time and accuracy do not always reflect the same perceptual processes; therefore, the convergence of reaction time with accuracy within the context of a specific information processing model should be demonstrated empirically rather than assumed a priori. (Author/PN)

This research was concerned with the way people identify and categorize letters and digits; the author attempted to answer which of these processes occurs first, with the focus on whether there is a logically determined sequence involved. (Author/RK)