Research from the past century has claimed empirical support for many different hypotheses–that men and women are fundamentally different because of biological reasons; that social influences (cultural factors) are the cause of male-female differences; and that men and women are not very psychologically different at all. Literature reviews and meta-analyses attempt to parse the truth by identifying in research alpha bias, which is the tendency to exaggerate differences, and beta bias, which is the tendency to minimize differences.