Phonology without semantics? Good enough for verbal short-term memory. Evidence from a patient with semantic dementia

There is considerable evidence that long-term knowledge has an influence on short-term memory (STM) performance. This reflects the activation of long-term representations involved in perceiving and comprehending spoken language. Still, this type of long-term knowledge might be of two different kinds. STM performance might be facilitated by information about the meaning of the word, or, alternatively, by familiarity with its phonological form.

We investigated these two alternatives by assessing word span in MC, a patient with semantic dementia. Four different lists of words were used: known words, words whose phonological form was known by the patient although she could not report its meaning, words that the patient did not recognize as words and judged as nonwords, nonwords. The patient's performance was compared to that of six matched controls.

MC did not differ from controls in the first two types of lists and performed at the same level with both, while for words whose phonological form was unknown (and therefore not recognized as words) her performance was comparable to that with nonwords; also, with this type of item, she produced significantly more phonemic substitutions than controls.

The results show that long-term knowledge facilitates immediate serial recall. However, this facilitation is due to familiarity with phonological representations rather than to knowledge of meaning.