The neomammalian brain is one of three aspects of Paul MacLean's Triune Theory of the human brain. MacLean was an American physician and neuroscientist who formulated his model in the 1960s, which was published in his own 1990 book The Triune Brain in Evolution. MacLean's three-part theory explores how the human brain has evolved from ancestors over millions of years, consisting of the reptilian, paleomammalian and neomammalian complexes. MacLean proposes that the neomammalian complex is only found in higher order mammals, for example, the human brain, accounting for increased cognitive ability such as motor control, memory, improved reasoning and complex decision-making.