ON THE RELATION BETWEEN TYPE OF ARRAYS AND TYPE OF ERRORS IN PARTIAL-REPORT BAR-PROBE STUDIES

In studies using Averbach and Coriell's (1961) partial-report bar-prob e task, the subject is requested to report the name of the indicated l etter in a briefly presented visual multi-letter display. In the error analysis for this task, Townsend (1973) distinguished errors that inv olved report of an item displayed in another than the indicated positi on (location errors) and errors that involved report of an item that w as not displayed (item errors). Furthermore, a location error was take n as an indication for inaccurate target localization and an item erro r for inaccurate target identification. Unfortunately, bar-probe studi es that applied this error analysis have yielded contradictory results as to the most frequent type of errors that was observed. Consequentl y, opposed interpretations were formulated as to the limiting factor ( either localization or identification) in human information processing capabilites for briefly presented material. These interpretations hav e in turn led to opposing views on the locus of selection of incoming information(later or early). In the present study, it is shown that (a ) the shape of the exposed letter arrays (linear or circular arrangeme nts) and (b) the letter identities and sampling procedure that are use d to compose the arrays (the whole alphabet and random sampling or a l imited set of letters and sampling while taking interletter confusabil ites into account) can explain the empirical incongruency. These two v ariables appear to affect (a) the accuracy of localization and identif ication processes and (b) the degree to which localization difficultie s are observable as location errors (and not as item errors) and ident ification difficulties as item errors (and not as location errors). In contrast with earlier claims, it is concluded that performance in par tial-report bar-probe tasks is constrained by two factors: localizatio n and identification.