In Miller's view, evolution is driven not just by natural selection, for survival, but equally importantly by the process that Darwin called sexual selection. In support of his views on sexual selection, he has written The mating mind: how sexual choice shaped the evolution of human nature. This revives and extends Darwin's suggestion that sexual selection through mate choice has been critical in human mental evolution—especially the more 'self-expressive' aspects of human behaviour, such as art, morality, language, and creativity. Identifying the 'survival value' of these traits has proved elusive, but their adaptive design features do suggest that they evolved through mutual mate choice by both sexes, to advertise intelligence, creativity, moral character, and heritable fitness. The supporting evidence includes human mate preferences, courtship behaviour, behaviour genetics, psychometrics, and life history patterns. The theory makes many testable predictions, and sheds new light on human cognition, motivation, communication, sexuality and culture.
Miller believes that our minds evolved not as survival machines, but as courtship machines, and proposes that the human mind's most impressive abilities are courtship tools, which evolved to attract and entertain sexual partners. By switching from a survival-centred to a courtship-centred view of evolution, he attempts to show how we can understand the mysteries of mind. The main competing theories of human mental evolution are (1) selection for generalist foraging ability (i.e., hunting and gathering), as embodied in the work of researchers such as Hillard Kaplan and Kim Hill at the University of New Mexico, and (2) selection for social intelligence, as argued by Andrew Whiten, Robin Dunbar, and Simon Baron-Cohen.
He has published on visual perception, cognition, learning, robotics, neural networks, genetic algorithms, human mate choice, evolutionary game theory, and the origins of language, music, culture, intelligence, ideology and consciousness. In particular, he studies human mental adaptations for judgment, decision-making, strategic behaviour and communication in social and sexual domains. Apart from mutual mate-choice and sexual selection theory, this includes work on:
His clinical interests are the application of fitness indicator theory to understand the symptoms, demographics, and behaviour genetics of schizophrenia and mood disorders. His other interests include the origins of human preferences, aesthetics, utility functions, human strategic behaviour, game theory, experiment-based economics, the ovulatory effects on female mate preferences, and the intellectual legacies of Darwin, Nietzsche and Veblen.
His research has provoked extensive media coverage. Currently, he is Assistant Professor of Psychology at the University of New Mexico.
He is co-editor of the volume Mating intelligence: Sex, relationships, and the mind's reproductive system, and is currently writing his second book, Faking fitness: the evolutionary origins of consumer behavior.