Does sleep protect memories against interference? A failure to replicate

Abstract

Across a broad spectrum of memory tasks, retention is superior following a night of sleep compared to a day of wake. However, this result alone does not clarify whether sleep merely slows the forgetting that would otherwise occur as a result of information processing during wakefulness, or whether sleep actually consolidates memories, protecting them from subsequent retroactive interference. Two influential studies suggested that sleep protects memories against the subsequent retroactive interference that occurs when participants learn new yet overlapping information (interference learning). In these studies, interference learning was much less detrimental to memory following a night of sleep compared to a day of wakefulness, an indication that sleep supports this important aspect of memory consolidation. In the current replication study, we repeated the protocol of and, additionally, we examined the impact of intrinsic motivation on performance in sleep and wake participants. We were unable to replicate the finding that sleep protects memories against retroactive interference, with the detrimental effects of interference learning being essentially the same in wake and sleep participants. We also found that while intrinsic motivation benefitted task acquisition it was not a modulator of sleep-wake differences in memory processing. Although we cannot accept the null hypothesis that sleep has no role to play in reducing the negative impact of interference, the findings draw into question prior evidence for sleep's role in protecting memories against interference. Moreover, the current study highlights the importance of replicating key findings in the study of sleep's impact on memory processing before drawing strong conclusions that set the direction of future research.

Does sleep-dependent consolidation favour weak memories?

“…This approach has been taken in a series of studies explicitly testing the protective effect of sleep against retroactive interference. Indeed, despite training participants to 100% pre-delay memory accuracy, the introduction of retroactive interference after the delay and before the final retrieval revealed a beneficial effect of sleep over wake, i.e., a sleep-dependent consolidation effect ( Ellenbogen, Hulbert, Jiang, & Stickgold, 2009 ; Ellenbogen et al., 2006 ; but see; Bailes, Caldwell, Wamsley, & Tucker, 2020 ; Pöhlchen, Pawlizki, Gais, & Schönauer, 2020 ). In line with these studies, we used retroactive interference to increase retrieval difficulty and thereby push memory performance from ceiling.…”

Understanding relational binding in early childhood: Interacting effects of overlap and delay

“…Relatively little is known about how young children's episodic memory performance changes when tested immediately or after a delay of 24 hours or more. In adults, a delay period filled with sleep as compared to an equivalent delay filled with wakefulness may protect against memory interference (Abel & Bäuml, 2014;Ellenbogen, Hulbert, Stickgold, Dinges, & Thompson-Schill, 2006;Sheth, Varghese, & Truong, 2012;Spencer, Sunm, & Ivry, 2006; but see also Bailes, Caldwell, Wamsley, & Tucker;Pöhlchen, Pawlizki, Gais, Schönauer;, likely due to sleep-related consolidation. Designs with delays up to 24 hours demonstrate that increases in the length of the delay between encoding and test increase forgetting (Payne et al, 2012;Takashima et al, 2009), but this decline is attenuated by sleep during the delay, especially if it directly follows learning (Payne et al, 2012).…”

Evidence against a large effect of sleep in protecting verbal memories from interference

“…In another study by the same group (Deliens, Schmitz, et al, 2013), retroactive interference was again specific to the sleep group, thereby contradicting the protective effect of sleep in the Ellenbogen studies. Among the recent studies on sleep and verbal interference, none reported beneficial effects of sleep with effect sizes as high as in the original study, leaving room for further investigations (Alger, Lau, & Fishbein, 2012; Bailes, Caldwell,, Wamsley, & Tucker, 2020; Deliens, Leproult, et al, 2013; Sheth et al, 2012).…”