Unlearning implicit social biases during sleep: A failure to replicate

Abstract

A 2015 article in Science (Hu et al.) proposed a new way to reduce implicit racial and gender biases during sleep. The method built on an existing counter-stereotype training procedure, using targeted memory reactivation to strengthen counter-stereotype memory by playing cues associated with the training during a 90min nap. If effective, this procedure would have potential real-world usefulness in reducing implicit biases and their myriad effects. We replicated this procedure on a sample of n = 31 college students. Contrary to the results reported by Hu et al., we found no effect of cueing on implicit bias, either immediately following the nap or one week later. In fact, bias was non-significantly greater for cued than for uncued stimuli. Our failure to detect an effect of cueing on implicit bias could indicate either that the original report was a false positive, or that the current study is a false negative. However, several factors argue against Type II error in the current study. Critically, this replication was powered at 0.9 for detecting the originally reported cueing effect. Additionally, the 95% confidence interval for the cueing effect in the present study did not overlap with that of the originally reported effect; therefore, our observations are not easily explained as a noisy estimate of the same underlying effect. Ultimately, the outcome of this replication study reduces our confidence that cueing during sleep can reduce implicit bias.

Targeted memory reactivation during sleep influences social bias as a function of slow‐oscillation phase and delta power

“…While meta‐analytical evidence of TMR convincingly suggests that memories can be selectively targeted and improved during SWS, the effect sizes of individual studies vary significantly (Hu et al, 2020). In the context of bias reduction, two studies were published, both conducted using a within‐subject manipulation and auditory TMR during an afternoon nap, with the first reporting a significant TMR effect and the second reporting a null effect (Hu, Antony et al, 2015; Humiston & Wamsley, 2019). One possible explanation for this divergence in effect size across studies would emphasize the small size of an underlying effect, such that real effects are sometimes missed when small sample sizes are used.…”

“…However, there was also ample heterogeneity of effect sizes across studies and the effect size tends to be small‐to‐moderate. With respect to TMR for social bias, only two studies have been published to date, our initial study (Hu, Antony et al, 2015) and one replication study where TMR benefits were not observed (Humiston & Wamsley, 2019). On the one hand, a divergence in TMR effect size between these two studies is unclear at present.…”

Cueing motor memory reactivation during NREM sleep engenders learning-related changes in precuneus and sensorimotor structures

“…This is especially true given that neither object-location 13 nor emotional 26 memory seems to benefit from the manipulation even a week later. One-week-later effects of TMR have been reported for implicit biases 27 , but this failed to replicate 28 . Our prior work showed behavioural effects of TMR 10 days post-manipulation but not 6 weeks later 11 .…”

Do all mammals dream?

“…The non‐REM type dreams might occur on a daily basis (except on the days when their sleep is disturbed, Gravett et al, ), but the REM type dreams might occur only every third or fourth day when the elephants take the opportunity to lie down to sleep, indicating muscle atonia associated with REM sleep. This potentially irregular occurrence of REM sleep, and the absence of any clear form of REM sleep in cetaceans (see above), provide an important phylogenetic counter‐argument to the hypothesized association between REM sleep and memory consolidation (Ackermann, Hartmann, Papassotiropoulos, de Quervain, & Rasch, ; Boyce, Glasgow, Williams, & Adamantidis, ; Humiston & Wamsley, , ; Magidov et al, ; Rasch, Pommer, Diekelmann, & Born, ; Siegel, ; Stickgold, ; Tilley & Empson, ; Wyatt, Fram, Kupfer, & Snyder, ).…”