Letter string processing and visual short-term memory.

The present study investigated whether expertise with letter string processing influences visual short-term memory capacity. Specifically, we examined whether performance in a change-detection task would vary as a function of stimulus type (letters vs. symbols) and type of display (horizontal, vertical, and circular). Participants were asked to detect a one-character change in a briefly presented character array following a delay of 900 ms. Concurrent articulation was used to limit effects of rehearsal. Type of display significantly affected performance with letters, but not with symbols, with a selective increase in change-detection accuracy for horizontally presented letter arrays compared with vertical and circular arrays. These findings confirm the standard limits of storage in visual short-term memory, but critically reveal a selective advantage for letter arrays over symbol arrays when presented horizontally. Such an advantage is probably due to the utilization of a specialized encoding mechanism built up over years of reading experience.