L Weiskrantz: Introductory remarks: categorization, cleverness, and conciousness; H J Jerison: Animal intelligence as encephalization; H B Barlow: Discussion; E M McPhail: Vertebrate intelligence: the null hypothesis; H B Barlow: Discussion; N J Mackintosh, B Wilson, & R A Boakes: Differences in mechanisms of intelligence among vertebrates; H B Barlow: Discussion; A Dickinson: Actions and habits: the development of behavioural autonomy; D D Olton: The temporal context of spatial memory; D Gaffan: Hippocampus: memory, habit, and voluntary movement; R E Passingham: Cortical mechanisms and cues for action; H S Terrace: Animal cognition: thinking without language; R J Herrnstein: Riddles of natural categorization; D I Perrett: Discussion; E W Menzel Jr & C Juno: Social foraging in marmoset monkeys and the question of intelligence; P Garrud: Discussion; Beatrix T Gardner & R A Gardner: Signs of intelligence in cross-fostered chimpanzees; E Sue Savage-Rumbaugh, Rose A Sevcik, D M Rumbaugh, & Elizabeth Rubert: The capacity of animals to acquire language: do species differences have anything to say to us?; D L Cheney & R M Seyfarth: Social and non-social knowledge in vervet monkeys; H Kummer & Jane Goodall: Conditions of innovative behaviour in primates; H J Jerison & L Weiskrantz: General discussion.