 From this follows the central empirical hypothesis of traditional BET: there should be bodily signatures for each basic emotion consisting of highly correlated and emotion-specific changes at the level of facial expressions, autonomic changes and preset and learned actions. More specifically, Ekman defined basic emotions in terms of (a) distinctive universal signals, (b) distinctive physiology, (c) distinctive thoughts, memories and images, (d) distinctive subjective experiences, (e) predictable developmental appearance, (f) homologous presence in other primates, (g) automatic appraisals tuned to distinctive universals in antecedent events, (h) quick onset, brief duration, and unbidden occurrence (Ekman 1999a: 5). Some basic emotion theorists have also suggested that basic emotions are associated with distinctive hardwired neural circuits (e.g., Izard 2011; Levenson 2011; Panksepp 1998, 2000).