The effectiveness of distractor-filtering is a potentially important determinant of working memory capacity (WMC). With three studies we interrogated distractor-filtering at WM encoding as opposed to filtering during maintenance, and their contributions to WMC. These studies involved both laboratory experiments, as well as a game for smartphones, which enabled large scale data-collection (eg. n = 3,247). For all three studies we measured WMC without distractors, and with distractors presented during encoding (Encoding Distraction, ED) or during the delay period of a WM task (Delay Distraction, DD) to determine performance associated with distraction at encoding and during maintenance.
Firstly, with young adults we observed a unique contribution to WMC from both ED and DD performance, while controlling for performance in the absence of distraction, indicating that separate mechanisms may contribute to WMC.
With the second study, we observed a further distinction between ED and DD filtering. As age increased during adulthood, performance was compromised more by DD than ED. However, with increasing age, the ability to exclude ED was a better predictor of WMC in the absence of distraction. A significantly greater contribution of distractor filtering at encoding represents a potential compensation for reduced WMC in older age.
Finally we investigated the different types of distractor filtering in patients with Parkinson’s Disease. Previous work has identified enhanced resistance to distraction in patients OFF dopaminergic medication. We observed reduced distraction costs for patients specifically for DD, but greater costs for ED, perhaps due to upregulated frontal dopamine levels and low striatal dopamine levels respectively.