Animal sexual behaviour however, is proving to be false as, "most hormones don’t influence behaviour directly. Rather, they affect thinking and emotions in variable ways (Azar, 40)." There is much more involved in sexual behaviour in the mammalian animal than oxytocin and vasopressin can explain. It is often assumed that animals do not have sex for pleasure, or alternatively that humans, pigs, bonoboes (and perhaps dolphins and one or two more species of primates) are the only species that do. This is sometimes stated as "animals mate only for reproduction". This view is considered a misconception by some scholars. Jonathan Balcombe argues that
Sex differences in humans is important in human psychology. Women have two X chromosomes while males have an X and Y chromosomal structure. The X chromosome is much more active than Y and it affects behavior. Genetic researchers theorize that the X chromosome may contain a gene responsible for sociability. Most IQ tests are constructed so that there are no overall score differences between females and males. Areas where differences have been found include verbal and mathematical ability. IQ tests that measure fluid "g" and have not been constructed to eliminate sex differences also tend to show that sex differences are either non-existent or