Do group ensemble statistics bias visual working memory for individual items? A registered replication of Brady and Alvarez (2011)

We performed a registered and precise replication of Experiment 1 reported in Brady and Alvarez (Psychological Science, 22, 384–392, 2011). The original experiment found that participants, who were asked to memorize the size of differently colored circles, reported the size of a probed circle biased toward the mean size of the same-colored group. Because our previous three unpublished replication attempts failed to find this effect, we powered the present registered replication using a Bayes Factor Design Analysis such that it provided compelling evidence regarding the presence or absence of the reported bias with a high probability, even under the assumption of smaller effect sizes. Thus, we recruited 663 participants through Amazon Mechanical Turk. We observed both a significant bias and strong Bayesian evidence in favor of the existence of a bias over the null hypothesis. Thus, our results can be considered a successful replication of the original findings, although with a considerably smaller effect size. We discuss the role of data quality when recruiting participants with Amazon Mechanical Turk. The present findings corroborate the idea that memory representations of individual objects are influenced by summary statistics.