processing are formed solely by one's sensory experiences. The notion is central to Lockean empiricism; it serves as the starting point for Locke's subsequent explication (in Book II) of simple ideas and complex ideas. As understood by Locke, tabula rasa meant that the mind of the individual was born blank, and it also emphasized the freedom of individuals to author their own soul. Individuals are free to define the content of their character—but basic identity as a member of the human species cannot be altered. This presumption of a free, self-authored mind combined with an immutable human nature leads to the Lockean doctrine of "natural" rights. Locke's idea of tabula rasa is frequently compared with Thomas Hobbes's viewpoint of human nature, in which humans are endowed with inherent mental content—particularly with selfishness. Freud (19th century) Tabula rasa also features in Sigmund Freud's psychoanalysis. Freud depicted personality traits as being formed by family dynamics (see Oedipus complex). Freud's theories imply that humans lack free will, but also that genetic influences on human personality are minimal. In Freudian psychoanalysis, one is largely determined by one's upbringing. Science Psychology and neurobiology Psychologists and neurobiologists have shown evidence that initially, the entire cerebral cortex is programmed and organized to process sensory input, control motor actions, regulate emotion, and respond reflexively (under predetermined conditions). These programmed mechanisms in the brain subsequently act to learn and refine the ability of the organism. For example, psychologist Steven Pinker showed that—in contrast to written language—the brain is "hard-wired" at birth to acquire spoken language. There have been claims by a minority in psychology and neurobiology, however, that the brain is tabula rasa only for certain behaviours. For instance, with respect to one's ability to acquire both general and special types of knowledge or skills, Michael Howe argued against the existence of innate talent. There also have been neurological investigations into specific learning and memory functions, such as Karl Lashley's study on mass action and serial interaction mechanisms. Important evidence against the tabula rasa model of the mind comes from behavioural genetics, especially twin and adoption studies (see below). These indicate strong genetic influences on personal characteristics such as IQ, alcoholism, gender identity, and other traits. Critically, multivariate studies show that the distinct faculties of the mind, such as memory and reason, fractionate along genetic boundaries. Cultural universals such as emotion and the relative resilience of psychological adaptation to