Skilled readers show different serial-position effects for letter versus non-letter target detection in mixed-material strings

Abstract

The study explored whether target detection in a five-character string depends on whether a letter or a non-letter was presented, as a predesignated target. Skilled readers had to identify a single letter or non-letter in a five-character string, randomly composed of letters and non-letters. It was found that an analytic processing strategy is automatically elicited if participants were instructed to detect a letter target. In this instance, a linear model best explained the RT variance for letters: with increasing RTs from left to right, suggesting a serial item-by-item reading-specific strategy comparable to alphabetic reading. For non-letters, in contrast, a symmetrical U-shaped function best explained the RT variance, suggesting a symmetrical scanning-out from the central to the terminal positions of the string. Since the design precludes orthographic and semantic influences, it can be concluded that a reading-specific strategy for alphabetic processing is automatically activated if the string is scanned for a letter-target. Thus, the pre-designated target triggers the strategy for processing the string and determines related position effects. The results suggest that effects from earlier studies, which showed an analytic processing preference for isolated letters (APPLE) in recognition tasks, as a consequence of literacy acquisition, generalize to the processing of letters in strings.