No effect of procedural memory interference on wakeful consolidation of episodic memory in younger and older adults

Episodic and procedural memory are conceptually and practically distinct: Episodic memories include personal experiences, facts, events, or objects, while procedural memories include skills and habits acquired gradually through practice. Brown and Robertson (2007) revealed that learning a procedural skill immediately after acquiring episodic memories disrupts the wakeful consolidation of episodic memories in young adults. This finding is commonly used as evidence that these two memory types are behaviorally antagonistic and should not be learned in close temporal proximity. However, to our knowledge, this finding has not been reproduced by an independent laboratory. Additionally older adults consistently show episodic memory deficits, but it is unknown whether procedural memory interference exacerbates these deficits. Therefore, we aimed to reproduce Brown and Robertson’s (2007) finding, while also investigating potential differences in the magnitude of procedural learning interference between younger and older adults. Our pre-registered study hypotheses were: 1) Procedural memory would interfere with the wakeful consolidation of episodic memory in both younger and older adults; 2) Older adults would experience significantly greater procedural memory interference on episodic memory than younger adults. Forty younger (18-40 years old; n =20) and older adults (≥55 years old; n = 20) visited the laboratory twice on the same day. In the morning, participants acquired episodic memories (a list of words) and then performed a procedural finger-tapping (procedural) task. During the afternoon session, participants were asked to recall the episodic memories from the morning session. Our analysis revealed no evidence of interference for both age groups or that the magnitude of interference between groups was different, despite using a more sensitive statistical analysis (linear mixed-effects modeling) and powering our study on the results of Brown and Robertson’s (2007) study. Our results call into question the robustness of this effect and suggest that it may be sensitive to factors such as inter-individual variation in episodic memory abilities or other experimental factors.