Is there a temporal basis of the word length effect? A response to Service (1998)

Service (1998) carried out a study of the word length effect with Finnish pseudowords in which short and long pseudowords were identical except for the inclusion of certain phonemes differing only in pronunciation length, a manipulation that is impossible in English. She obtained an effect of phonemic complexity but little or no word duration effect per se--a discrepancy from the expectations generated by the well-known working memory model of Baddeley (1986). In the present study using English words, we controlled for phonemic complexity differences by using the same words for the short- and long-word sets, but with instructions inducing shorter or longer pronunciation of the words. We obtained substantial word duration effects. Concerns raised by Service are addressed, and we conclude that both duration and complexity are likely to contribute to the word length effect in serial recall.

Persistence of memory for ignored lists of digits: areas of developmental constancy and change.

Contrary to the common belief that sensory memory remains unchanged across development in childhood, there have been several previous reports suggesting that the persistence of sensory memory, at least for sounds, increases with age in childhood. Because those previous studies all used isolated sounds as stimuli, it is not yet clear how this developmental difference influences the recall of sound series. The present study adapts the procedure of J. S. Saults and N. Cowan (1996), who studied memory for attended and ignored spoken words, to examine here the recall of attended and ignored lists of digit. A developmental increase in the persistence of memory was obtained only for the final item in an ignored list, which is the item for which sensory memory is thought to be the most vivid at short retention intervals.

The role of attention in the development of short-term memory: age differences in the verbal span of apprehension.

In previous studies of memory span, participants have attended to the stimuli while they were presented, and therefore have had the opportunity to use a variety of mnemonic strategies. In the main portion of the present study, participants (first- and fourth-grade children, and adults; 24 per age group) carried out a visual task while hearing lists of spoken digits and received a post-list digit recall cue only occasionally, for some lists. Under these conditions, list information presumably must be extracted from a passively held store such as auditory sensory memory. The results suggest that each individual has a core memory capacity limit that can be observed clearly in circumstances in which it cannot be supplemented by mnemonic strategies, and that the capacity limit appears to increase with age during childhood. Other, attention-demanding processes also contribute to memory for attended lists.

Two separate verbal processing rates contributing to short-term memory span.

Previous research indicates that verbal memory span, the number of words people can remember and immediately repeat, is related to the fastest rate at which they can pronounce the words. This relation, in turn, has been attributed to a general or global rate of information processing that differs among individuals and changes with age. However, the experiments described in this article showed that the rates of 2 processes (rapid articulation and the retrieval of words from short-term memory) are related to memory span but not to each other. Memory span depends on a profile of processing rates in the brain, not only a global rate. Moreover, there appears to be only a partial overlap between the rate variables that change with age and those that differ among individuals.