The Microbiome in Psychology and Cognitive Neuroscience

Psychology and microbiology make unlikely friends, but the past decade has witnessed striking bidirectional associations between intrinsic gut microbes and the brain, relationships with largely untested psychological implications. Although microbe–brain relationships are receiving a great deal of attention in biomedicine and neuroscience, psychologists have yet to join this journey. Here, we illustrate microbial associations with emotion, cognition, and social behavior. However, despite considerable enthusiasm and potential, technical and conceptual limitations including low statistical power and lack of mechanistic descriptions prevent a nuanced understanding of microbiome–brain–behavior relationships. Our goal is to describe microbial effects in domains of cognitive significance and the associated challenges to stimulate interdisciplinary research on the contribution of this hidden kingdom to psychological processes. All known multicellular life is colonized by microbes. The gut microbiome is a highly complex and diverse hidden kingdom that inhabits the intestinal tracts. Gut microbes are associated with important psychophysiological functions, including neurodevelopment and neurotransmission, emotion and stress, learning and memory, social behavior, autism, and aging. We call for the greater involvement of psychologists and cognitive scientists in understanding bacterial contributions to psychological processes.