Jaak Panksepp's pioneering affective neuroscience research fundamentally changed how scientists understand play. He identified seven primary emotional systems shared across mammals — including the PLAY system — demonstrating that these are genetically encoded subcortical circuits with very early evolutionary origins. He coined the term 'affective neuroscience' in the early 1990s, and his 1998 text on the subject became a core textbook. His studies of rat 'laughter' during tickling and play, his identification of play deprivation as a primal drive, and his demonstration that play activates genes essential for healthy brain development rank among the most important findings in play science. He was Baily Endowed Chair of Animal Well-Being Science at Washington State University until his death in April 2017.
