The adaptationist approach is steadily increasing as an influence in the general field of psychology. Evolutionary psychologists hold that behaviours or traits which occur universally in all cultures are good candidates for evolutionary adaptations. This includes our ability to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.