His primary research focus is on strategies of human mating. He is most well-known for his studies on mate selection, tactics of mate attraction, infidelity, tactics of mate retention, tactics of mate poaching, and the mating emotions of jealousy, lust, and love.

His recent research focuses on the dark side of human nature, including conflict between the sexes, jealousy, stalking, intimate partner violence, and murder. He also has active research programs on the mating emotions and the psychology of prestige, status, and reputation.