When Does Length Cause the Word Length Effect?

Annie Jalbert and Ian Neath Memorial University of Newfoundland

Tamra J. Bireta The College of New Jersey

Aime?e M. Surprenant Memorial University of Newfoundland

The word length effect, the finding that lists of short words are better recalled than lists of long words, has been termed one of the benchmark findings that any theory of immediate memory must account for. Indeed, the effect led directly to the development of working memory and the phonological loop, and it is viewed as the best remaining evidence for time-based decay. However, previous studies investigating this effect have confounded length with orthographic neighborhood size. In the present study, Experi- ments 1A and 1B revealed typical effects of length when short and long words were equated on all relevant dimensions previously identified in the literature except for neighborhood size. In Experiment 2, consonant–vowel– consonant (CVC) words with a large orthographic neighborhood were better recalled than were CVC words with a small orthographic neighborhood. In Experiments 3 and 4, using two different sets of stimuli, we showed that when short (1-syllable) and long (3-syllable) items were equated for neighborhood size, the word length effect disappeared. Experiment 5 replicated this with spoken recall. We suggest that the word length effect may be better explained by the differences in linguistic and lexical properties of short and long words rather than by length per se. These results add to the growing literature showing problems for theories of memory that include decay offset by rehearsal as a central feature.

Keywords: word length, orthographic neighborhood, working memory

The word length effect, the finding that lists of short words (e.g., cat, boat, pear, etc.) are recalled better than lists of long words (e.g., gorilla, hovercraft, banana, etc.) has played such a signifi- cant a role in the development of theories of memory that it is now regarded as a “benchmark finding” that current theories of short- term or working memory must address (cf. Lewandowsky & Farrell, 2008). Indeed, the basic finding is one of the core phe- nomena that led directly to the development of the phonological loop component of working memory (Baddeley, 1992), has been termed the “best remaining solid evidence” for the existence of such temporary memory systems (Cowan, 1995, p. 42), and is the focus of many computational models (e.g., Brown & Hulme, 1995;

Burgess & Hitch, 1999; Hulme, Surprenant, Bireta, Stuart, & Neath, 2004; Neath & Nairne, 1995; Page & Norris, 1998). In this article, we consider evidence that questions the idea that length per se is the critical factor underlying the word length effect.

The first systematic exploration of the word length effect was reported by Baddeley, Thomson, and Buchanan (1975), although the basic finding was known earlier (e.g., Watkins, 1972). In a series of experiments, Baddeley et al. (1975) identified two ways in which word length can have an effect on memory performance. The time-based word length effect is shown with words that are equated on all dimensions, including the number of syllables and phonemes, but vary systematically only in the time required to pronounce the words. In contrast, the syllable-based word length effect is demonstrated when the short and long words vary not only in pronunciation time but also in the number of syllables and phonemes.

According to the working memory framework, both effects are explained in the same way: Items in the phonological loop decay within about 2 s if not refreshed by an articulatory control process. Given the assumption that there is a positive correlation between the rate of subvocal rehearsal and overt pronunciat