“Those Evenings of the Brain – When Not a Moon Disclose a Sign”

We were invited to make a response to Gargus’s and Haier’s (Gargus & Haier, 2025) paper Toward a Molecular Biology of Human Intelligence: Psychometrics Meets Gene Expressions and Brain Metabolism . We’re tramping ‘toward’ that goal too. Our comments recognise that the authors have pointed to some biological loci/concepts that might help with understanding intelligence differences. We muse on what genomic and brain imaging studies have contributed, and their limitations. Mostly, the reader will note our efforts (sometimes not successful) at trying not to appear overwhelmed by the off-putting complexity of explaining how differences arise in intelligence and other complex traits. Note : The title of this paper comes from Emily Dickinson’s poem, “We Grow Accustomed to the Dark.”