ABSTRACT
Some of our most basic daily activities require the ability to retain serial order information in working memory. For example, auditory word perception depends on retaining the order in which phonemes occurred until the appropriate lexical entry has been activated. Experimentally, the retention of serially ordered verbal information has been examined by determining the effect of various factors on memory span—the length of a word or nonword list that can be immediately recalled in correct order 50% of the time. A large body of evidence supports the role of phonological codes in memory span performance. For example, memory span is smaller for phonologically similar than for phonologically dissimilar items (Conrad & Hull, 1964; Hintzman, 1965; Luce, Feustel, & Pisoni, 1983; Sperling & Speelman, 1970; Wickelgren, 1966) and is smaller for items taking longer to pronounce (Baddeley, Thomson, & Buchanan, 1975; Mackworth, 1963; Schweickert & Boruff, 1986). Some theories have postulated a short-term store specifically dedicated to the retention of phonological information (e.g. Baddeley, 1986; Cowan et al., 1992; Schweickert & Boruff, 1986). Other evidence, however, supports a contribution from lexical and semantic factors in verbal serial recall. For example, span performance is greater for words than for nonwords, suggesting that the lexical information provided by words is represented in short-term memory (Brener, 1940; Crowder, 1978; Hulme, Maughan, & Brown, 1991). Saffran and N. Martin (1990) have observed effects of two other lexical variables, imageability and frequency, on span performance. Theorists noting these non-phonological contributions have emphasised the relation between the codes and processes involved in language processing and those involved in word list recall (e.g. R. Martin, Shelton, & Yaffee, 1994; N. Martin & Saffran, 1992a,b). In the present research, two theories taking the latter approach are examined for their adequacy in accounting for the relations between language processing and list recall for three aphasic patients.
