title: The power of associative learning and the ontogeny of optimal behaviour.
abstract: Behaving efficiently (optimally or near-optimally) is central to animals' adaptation to their environment. Much evolutionary biology assumes, implicitly or explicitly, that optimal behavioural strategies are genetically inherited, yet the behaviour of many animals depends crucially on learning. The question of how learning contributes to optimal behaviour is largely open. Here we propose an associative learning model that can learn optimal behaviour in a wide variety of ecologically relevant circumstances. The model learns through chaining, a term introduced by Skinner to indicate learning of behaviour sequences by linking together shorter sequences or single behaviours. Our model formalizes the concept of conditioned reinforcement (the learning process that underlies chaining) and is closely related to optimization algorithms from machine learning. Our analysis dispels the common belief that associative learning is too limited to produce 'intelligent' behaviour such as tool use, social learning, self-control or expectations of the future. Furthermore, the model readily accounts for both instinctual and learned aspects of behaviour, clarifying how genetic evolution and individual learning complement each other, and bridging a long-standing divide between ethology and psychology. We conclude that associative learning, supported by genetic predispositions and including the oft-neglected phenomenon of conditioned reinforcement, may suffice to explain the ontogeny of optimal behaviour in most, if not all, non-human animals. Our results establish associative learning as a more powerful optimizing mechanism than acknowledged by current opinion.
authors.affiliation: Centre for the Study of Cultural Evolution, Stockholm University, Lillafrescativägen 7B, 106 91 Stockholm, Sweden; Department of Zoology, Stockholm University, Svante Arrheniusvägen 14D, 106 91 Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Enquist
authors.affiliation: Centre for the Study of Cultural Evolution , Stockholm University , Lillafrescativägen 7B, 106 91 Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Lind
authors.affiliation: Centre for the Study of Cultural Evolution, Stockholm University, Lillafrescativägen 7B, 106 91 Stockholm, Sweden; Department of Psychology, Brooklyn College, 2900 Bedford Avenue, Brooklyn, NY 11210, USA; Department of Psychology, Graduate Center of the City University of New York, 365 5th Avenue, New York, NY 10016, USA; Department of Biology, Graduate Center of the City University of New York, 365 5th Avenue, New York, NY 10016, USA.
authors.forename: Stefano
authors.identifier: 0000-0002-7270-9612
authors.initials: S
authors.lastname: Ghirlanda
keywords: animal cognition; animal learning; conditioned reinforcement; optimal behaviour; reinforcement learning