Goldberg reviews literature, gathering evidence from expert witnesses (both primary and secondary sources) to demonstrate that each of three distinct patterns of recognised human social behaviour (institutions) has been observed in every known society. He proposes that these three universal institutions, attested as they are across independent cultures, suggest a simple psychophysiological cause, since physiology remains constant, as do the institutions, even across variable cultures--a universal phenomenon suggests a universal explanation. The institutions Goldberg examines are patriarchy, male dominance and male attainment. The hypothetical psychophysiological phenomenon he proposes to explain them, he denotes by the expression differentiation of dominance tendency. He explains this refers to dominance behaviour being more easily elicited from men on average than from women on average. In other words, he theorises a biologically mediated difference in preferences.