A long-standing, controversial theory suggests that species with larger brains relative to their body size are more intelligent. A new study found evidence that strongly supports this long-held belief.
A research team led by University of Wyoming's Sarah Benson-Amram found that carnivore species with relatively larger brains that are proportionate to their body size are better at completing problem-solving tasks. Benson-Amram is an assistant professor from the university's Department of Zoology and Physiology.
Along with fellow authors Eli Swanson (University of Minnesota), Kay Holekamp, Greg Stricker and Ben Dantzer (Michigan State University), Benson-Amram traveled to nine zoos across the United States. The team chose 140 animals from 39 different mammalian carnivore species and presented them with a new problem-solving task.
The animals involved in the study included arctic foxes, polar bears, tigers, spotted hyenas and wolves, among others. The team presented each animal with a metal box containing their favorite food. They were given only 30 minutes to extract it. The metal box can be opened by a sliding bolt latch.
Results showed that animals with larger brains that are proportionate to their body size were more successful in gaining access to the food compared to the animals with smaller brains. The study was published in the journal Proceedings of the National Academy of Sciences.
"This study offers a rare look at problem solving in carnivores, and the results provide important support for the claim that brain size reflects an animal's problem-solving abilities - and enhance our understanding of why larger brains evolved in some species," said Benson-Amram.
In total, 35 percent of the animal participants successfully finished the problem-solving task. They composed of 49 animals from 23 species. The bears, who topped the ranking, were able to solve the problem 70 percent of the time. The least successful participants were the mongooses and meerkats.
The team noted that overall, smaller-bodied animals were more successful than the larger ones. Moreover, manual dexterity has no effect on the animals' success rate in problem-solving.
The researchers also analyzed if species who live in larger groups are more intelligent when it comes to problem-solving tasks. The so-called "social brain hypothesis" suggests that larger brain sizes evolved in order to handle the social domain challenges.
It also says that intelligence progressed to help animals respond, anticipate and even manipulate others' actions in their social groups. The team didn't find any evidence that supports the "social brain hypothesis."
You can watch the video below to see how different animals performed.
Photo: NPS/K. Jalone | Flickr