Role of phonological discrimination and inhibition in a short-term memory precision task in young and older adults

Short-term memory (STM) precision is defined as the resolution at which items are stored in STM. It has to be distinguished from STM capacity which is characterized by a binary dimension: items are recalled or forgotten. STM precision refers to the notion that all items are available in memory, but their representation varies in terms of accuracy. Few studies have considered verbal STM precision and none of them has investigated STM precision from a lifespan perspective neither its links with inhibition capacity.
The present study assessed young and elderly adults’ sensitivity to gradients of phonological similarity between target and probe items in a short-term recognition task. Moreover, executive tests (Stroop, Plus Minus, N-Back) and a discrimination task using the same items as the main STM precision task were administered.
Using ANOVA, we observed strong evidence for a graded influence of phonological similarity on STM probe recognition. No age effect was observed, which suggest that phonological precision assessed in an auditory recognition task is stable across adulthood. We further investigate if executive functions and auditory discrimination explain performances when target and probe items are phonologically close. Using Multiple Linear Regression, results indicated that auditory discrimination and inhibition appeared to be the main predictors of incorrect recognition when probe items are phonologically highly similar to target items.
This study suggests that phonological similarity is a useful variable for the investigation of the concept of precision in verbal STM. It further indicates that the precision of verbal STM coding could be preserved in aging, at least at the phonological level. This study rises interrogations on the role of inhibition in STM precision.