rsfs.royalsocietypublishing.org Research Cite this article: Mikhalevich I, Powell R, Logan C. 2017 Is behavioural flexibility evidence of cognitive complexity? How evolution can inform comparative cognition. Interface Focus 7: 20160121. http://dx.doi.org/10.1098/rsfs.2016.0121 One contribution of 12 to a theme issue ‘Convergent minds: the evolution of cognitive complexity in nature’. Subject Areas: biocomplexity, astrobiology Keywords: behavioural flexibility, cognition, convergence, Morgan’s canon, simplicity Author for correspondence: Russell Powell e-mail: rpowellesq@gmail.com Is behavioural flexibility evidence of cognitive complexity? How evolution can inform comparative cognition Irina Mikhalevich 1 , Russell Powell 2 and Corina Logan 3 1 School of Mind and Brain, Humboldt-Universitat zu Berlin, Berlin, Germany 2 Department of Philosophy, Boston University, Boston, MA 02215, USA 3 Department of Zoology, University of Cambridge, Cambridge, UK RP, 0000-0002-9893-1721; CL, 0000-0002-5944-906X Behavioural flexibility is often treated as the gold standard of evidence for more sophisticated or complex forms of animal cognition, such as planning, metacognition and mindreading. However, the evidential link between behavioural flexibility and complex cognition has not been explicitly or systematically defended. Such a defence is particularly pressing because observed flexible behaviours can frequently be explained by putatively sim- pler cognitive mechanisms. This leaves complex cognition hypotheses open to ‘deflationary’ challenges that are accorded greater evidential weight precisely because they offer putatively simpler explanations of equal explana- tory power. This paper challenges the blanket preference for simpler explanations, and shows that once this preference is dispensed with, and the full spectrum of evidence—including evolutionary, ecological and phylo- genetic data—is accorded its proper weight, an argument in support of the prevailing assumption that behavioural flexibility can serve as evidence for complex cognitive mechanisms may begin to take shape. An adaptive model of cognitive-behavioural evolution is proposed, according to which the existence of convergent trait–environment clusters in phylogenetically dis- parate lineages may serve as evidence for the same trait–environment clusters in other lineages. This, in turn, could permit inferences of cognitive complexity in cases of experimental underdetermination, thereby placing the common view that behavioural flexibility can serve as evidence for complex cognition on firmer grounds. 1. Introduction According to the standard view in comparative cognition science, animal cogni- tion is generally held to consist in the processes that generate flexible adaptive behaviours in animals [1]. This conception of cognition is motivated by the prima facie plausible assumption that flexible behaviour is underwritten by cog- nitive processes, and that the more flexible the observed behaviour, the more complex the cognitive processes that underlie it are likely to be (e.g. [2]). This assumption shapes research programmes in comparative cognition, where behav- ioural flexibility is often treated not only as the gold standard but also as the only significant source of evidence for cognitive complexity [3–5]. Experiments are designed to elicit flexible behaviours that respond appropriately to environmental contingencies, and the observations of such behaviours are, in turn, thought to license inferences about the presence (or absence) of a cluster of cognitive abilities that are generally, if problematically (§2), regarded in the literature as being sophisticated or complex—such as planning, concept formation, metacognition, mindreading and so on [6]. Despite the received view among comparative cognition researchers and phi- losophers of comparative cognition science that flexible behaviours can serve as & 2017 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. on April 21, 2017 http://rsfs.royalsocietypublishing.org/ Downloaded from