Evolution of Intelligence

Intelligence presents evolutionary biology with one of its greatest challenges. Despite considerable interest in, and decades of research into, the evolution of intelligence, there is still little consensus on how we should measure intelligence in animals. Likewise, leading theories on the evolution of intelligence have mixed support and drivers of intelligence appear to be variable across taxa. Thus, there is a critical need to expand studies of the evolution of intelligence beyond the traditionally studied primates. Our research investigates the evolution of intelligence in mammalian carnivores using both mechanistic and functional approaches. To study the mechanisms of intelligence, we examine neurobiological correlates of problem-solving performance both across and within species. To elucidate the evolutionary drivers of intelligence, we test predictions of the leading hypotheses explaining the evolution of intelligence.

Most likely, intelligence evolved as a result of a combination of many of these factors. We are testing hypotheses to explain the evolution of sophisticated intelligence using members of the order Carnivora as a model group. Specifically, our lab has examined innovative problem-solving abilities across a range of carnivore species with varying degrees of social and ecological complexity.

Project collaborators

Major findings from this theme

1. Relative brain size predicts problem-solving performance in mammalian carnivores. To study the evolution of cognition in a comparative framework, we need a measure of intelligence. In many past studies, it was assumed that having a larger brain relative to body size was related to intelligence. However, there is very little experimental evidence demonstrating a relationship between relative brain size and advanced cognitive abilities. We collaborated with Dr. Kay Holekamp (Michigan State University) and Dr Ben Dantzer (University of Michigan) to present 140 animals from 39 mammalian carnivore species with a novel problem-solving task. We found that species with larger brains relative to their body size were more successful at solving this task than species with relatively smaller brains. This study provides important support for the claim that relative brain size reflects an animal’s problem-solving abilities and enhances our understanding of why larger brains evolved in some species.

2. There are differences in the brains of cognitively flexible raccoons and cognitively inflexible raccoons. We are collaborating with neuroscientists (Dr. Kelly Lambert (University of Richmond) and Dr. Suzana Herculano-Houzel (Vanderbilt University)) to examine the neurobiological basis of behavioral flexibility. We recently found that behaviorally flexible raccoons, defined as those raccoons that are able to open a novel puzzle box in three different ways, have more cells in their hippocampus and more von Economo or fusiform-shaped neurons in their dentate gyrus than unsuccessful raccoons. There is no difference in cell number between successful and unsuccessful raccoons in control brain areas that are not implicated in learning and memory, such as the somatosensory cortex. These results provide another link between neurobiological measures and performance on cognitive tasks.

3. Spotted hyenas demonstrate complex cognitive abilities like those seen in primates such as baboons and vervet monkeys. In collaboration with Kay Holekamp (Michigan State University), I examined problem-solving abilities and learning in wild spotted hyenas by investigating their responses to a novel technical problem. These experiments illuminated the role of the diversity of initial exploratory behaviors, persistence, and neophobia in determining innovative problem-solving success. Specifically, we found that wild hyenas that showed a greater diversity of behaviors when they first encountered a novel problem were more successful than hyenas that tried fewer behaviors. Also, we found that hyenas that showed less fear of the puzzle box when they first saw it, measured as the time it took them to approach the box, were more successful than more fearful (or neophobic) hyenas. Finally, we found that more persistent hyenas were also more successful than hyenas that gave up more quickly. We also conducted playback experiments demonstrating that hyenas can assess the number of simulated intruders in their territory and respond appropriately based on numerical advantage. These experiments show that spotted hyenas possess cognitive abilities like those seen in cercopithecine primates, following predictions of the Social Intelligence Hypothesis.

Media coverage

• New York Times: Watch a video describing our work created by James Gorman and the team of ScienceTake at the New York Times

• New York Times: Many Animals Can Count, Some Better Than You

• Science News: In a tally of nerve cells in the outer wrinkles of the brain, a dog wins

• New Scientist: Watch brainy zoo animals figure out a box puzzle to get at food

• BBC, “Talking to the Animals” television program, July 2014 on BBC channel 1.

• National Public Radio, Academic Minute, March 2013: Dr. Sarah Benson-Amram, University of St. Andrews – Measuring Intelligence in Wild Animals

• NBC News, January 2013: Captive hyenas beat wild peers in puzzle solving

• Popular Science, January 2013: Captive Hyena Figures Out A Meat Puzzle Faster Than Its Wild Cousin

• Nature, Research Highlights, 15 August 2012: Curious hyenas crack puzzles

• PBS Nature, August 2012: Faced with a steel box, hyenas try to think outside it

• BBC Radio Wales, Good Morning Wales, September 2012: A live interview with Dr. Benson-Amram

• Sunday Telegraph, September 2012: Hyenas are as bright as primates, research shows

• Nature News, August 2011: Hyenas can count like monkeys

• Scientific American, August 2011: Hyenas Can Count Like Monkeys

• National Public Radio, Morning Edition, February 2009: Laughing's No Joke For Spotted Hyenas

• New York Times, March 2008: Sociable, and Smart

• Smithsonian Magazine, May 2008: Who’s Laughing Now?

Other videos describing our work with hyenas are available here:

• https://www.youtube.com/watch?v=AR5WBYtcUXA

• https://www.youtube.com/watch?v=tF8pks9Ho-4&feature=relmfu

• https://www.youtube.com/watch?v=xtOBJ0EjJIY

Featured publications

• Jacob, J., Kent, M., Benson-Amram, S., et al. 2021. Cytoarchitectural characteristics associated with cognitive flexibility in raccoons. Journal of Comparative Neurology, DOI: 10.1002

• Johnson-Ulrich, L., Benson-Amram, S., Holekamp, K. 2019. Fitness consequences of innovation in spotted hyenas. Frontiers in Ecology and Evolution, 7, 443, DOI: 10.3389

• Holekamp K.E., Benson-Amram S. 2017. The evolution of intelligence in mammalian carnivores. Interface Focus 7 : 20160108. (pdf)

• Benson-Amram, S. , Dantzer, B. , Stricker, G. , Swanson, E.M., Holekamp, K.E. 2016. Brain size predicts problem-solving ability in mammalian carnivores. Proceedings of the National Academy of Sciences, 113(9), 2532-2537. (pdf)

• Holekamp, K.E., Dantzer, B., Stricker, G.M., Shaw, Yoshida K.C., and Benson-Amram, S. 2015. Brains, brawn and sociality: a hyaena's tale. Animal Behavior, 103, 237-248. (pdf)

• Benson-Amram, S., Heinen, V. K., Dryer, S. L. & Holekamp, K. E. 2011 Numerical assessment and individual call discrimination by wild spotted hyaenas, Crocuta crocuta. Animal Behaviour 82, 743–752.

• Benson-Amram, S., Gilfillan, G. & McComb, K. 2018 Numerical assessment in the wild: insights from social carnivores. Philosophical Transactions of the Royal Society B Biological Sciences 373, 20160508.

• Benson-Amram, S., Weldele, M. L. & Holekamp, K. E. 2013 A comparison of innovative problem-solving abilities between wild and captive spotted hyaenas, Crocuta crocuta. Animal Behaviour, 85, 349-356

• Benson-Amram, S. & Holekamp, K. E. 2012 Innovative problem solving by wild spotted hyenas. Proceedings of the Royal Society B Biological Sciences 279, 4087–4095.