Short-term memory (STM) impairments are prevalent in adults with acquired brain injuries. The majority of standard STM tests require speech production, e.g. forward digit span, making them unsuitable for people with aphasia (word finding difficulties) and motor speech disorders (speech demands). One alternative task is the matching span task whereby a person hears two word-lists and indicates if the words in the lists were in the same or different order. Despite being a relatively popular method for assessing STM, normative data are not available, and its psychometric properties have not been investigated, This study aimed to provide normative data for matching span tasks involving digits, words and non-words and develop a custom software application (MEMO), based on the matching span task for use in assessment and treatment of STM deficits in aphasia.
MEMO was used to present test stimuli and generate norms for digits, words and non-words with 30 adults (>65 years) recruited from South-West Ireland, North-East England and Central Scotland. Test-retest reliability was examined with 12 participants. Additional analyses investigated the robustness of the data in relation to sampling methods, such as age, level of education and recruitment location.
Test-retest reliability was acceptable for digits, good for non-words but unacceptable for words. Education, gender and recruitment location did not influence STM capacity. There was a moderate negative correlation between STM capacity for words and non-words, suggesting lexical-semantic knowledge may contribute to phonological processing and STM capacity.
This is the first study providing normative data from healthy older adults and comparing STM performance across different lexical items. The use of computers in delivering STM assessment affords accuracy and timing precision. Matching span tasks have variable test-retest reliability, depending upon their lexical content. MEMO is a flexible tool for collecting normative data using different types of verbal stimuli with potential for treatment.