Date Published: January 25, 2019
Publisher: Public Library of Science
Author(s): Graelyn B. Humiston, Erin J. Wamsley, Michael B. Steinborn.
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.
Non-conscious biases are ubiquitous in social interactions, perpetuating discrimination even among people who do not explicitly endorse prejudiced beliefs [1–3]. For example, laboratory studies of hiring decisions demonstrate that participants who report no explicit racial bias nonetheless favour light-skinned candidates . These implicit biases are insidious particularly because of their non-conscious, unintentional nature, as even persons with a strong implicit bias may not perceive any discrimination in their thoughts and actions, and may thus be unaware of their consequences . Therefore, it is imperative to develop and disseminate procedures that effectively reduce these implicit biases and mitigate their impact on society.
In this replication study, we failed to find evidence that TMR strengthens the effects of counter-bias training, either immediately or after a 1-week delay. This decreases our confidence that TMR can be used to reduce implicit social biases.