Innovating Innovation Rate and Its Relationship with Brains, Ecology and General Intelligence

the ecology of intelligence, while Wyles et al. [1983] had proposed that innovations, especially when they were socially transmitted, might serve as behavioral drivers of evolution, using the famous example of tits opening milk bottles. Around 1994, I started wondering whether there could be many more cases of innovations besides milk bottle opening hidden in the ornithology literature, and whether these cases could provide a valid quantitative estimate of cognition. The publication of McGill Biology colleague Rob Peters’ influential book The Ecological Implications of Body Size [Peters, 1983] (currently 3,920 citations on Google Scholar) gave me a kind of ‘quantification envy’ that animal cognition could be as ‘operationalizable’ as body size and used in a similar manner in comparative analyses. Initially, the innovation project targeted taxonomic differences in socially acquired versus individually acquired innovations, predicting that, if the taxonomic distribution of the two modes of acquisition did not differ, this would be further support for the argument that social and individual learning are different sides of the same coin. The socially acquired category was soon dropped because too few cases were found in birds, but the data did show for the first time that a field-based quantitative measure of intelligence was positively correlated with relative forebrain size [Lefebvre et al., In 2002, the three of us were working together at McGill University, brought together by our shared interest in animal innovation. We had begun to discuss writing a review on the different aspects of our work on behavioral flexibility, which we felt strengthened and supported one another. An ideal opportunity arose when then editor Walt Wilczynski devoted a special issue of BBE to a symposium on ‘Ecology and the Central Nervous System’, organized by Luc-Alain Giraldeau at the 2002 International Society for Behavioral Ecology congress in Montreal. In the paper we were able to discuss and review a new operational measure of cognition, innovation rate. Using innovation rate and related measures of behavioral flexibility, we provided evidence for convergent cognitive evolution in birds and primates, and for behavioral flexibility having important ecological and evolutionary consequences. Broadly, our contributions can be separated into three themes, and we discuss the genesis of each in turn.