A review of 11 meta-analyses on anomalous cognition, covering over 80 years of research, indicates that such phenomena appear possible. Effect sizes are larger when studies use non-ordinary or altered states of consciousness (e.g., dreaming, ganzfeld), free-response procedures, or neurophysiological dependent variables. These conditions seem to facilitate a form of cognition not constrained by known biological sensory or brain limits. The findings broaden understanding of the mind-brain relationship and the nature of the human mind.
Dream-ESP is a form of extrasensory perception in which a sleeping person supposedly gains information about a randomly selected target without using normal senses or logic. A meta-analysis of studies from 1966 to 2016 found significant effects supporting the ESP hypothesis. A critique by Howard (2018) reported much weaker effects after re-analyzing the data using inverse-variance weights. While Howard replicated some findings, other results are disputed. The authors discuss meta-analytic methods, including publication bias and handling outliers, and present re-analyses challenging some of Howard's conclusions.