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Why some animals can know more from less


However, phylogeny can only tell scientists so much. The team wondered if the difference might have something to do with the animals’ neurophysiology. But they weren’t sure which aspect of the brain to measure.

In the past, researchers often used the total brain mass of animals as a measure of cognitive ability. Basically, the bigger the better. But when Bryer and Koopman pulled out the data, they found a weak correlation between brain size and quantitative sensitivity. They turned to a relatively new metric — cortical neurons Density—Which tells scientists how many neurons the brain has in its cortex. (The cerebral cortex is the outer tissue layer of the mammalian brain and is involved in complex cognition.)

Don’t shred words: To quickly count the number of neurons per milligram of brain, a researcher must liquefy it. (“She calls it ‘brain soup,’” Cantlon says of Vanderbilt University neuroscientist Suzana Herculano-Houzel, who developed the method. “) In this case, the researchers used a dataset from Herculano -Houzel’s Laboratories, which collects published data on neuronal density for 12 species. Here, the correlation The relationship was clear: Neural density had the greatest effect on quantitative sensitivity among all tested indicators, including characteristics such as family size and social group size. neuronal levels are largely constrained by a species’ genes, the team sees as additional evidence that evolution plays a huge role.

The magic of neuron density is that it has consequences for cognition, but it’s surprisingly independent of brain size. For some mammals, larger brains may have larger neurons and therefore lower density. But that is not the general rule. It is simply its own thing. Smaller neurons, with smaller branches, can pack together more tightly and give the brain a more detailed sense of the world. “Think about the number of pixels in a camera: The more pixels, the higher the resolution,” said Herculano-Houzel, who was not involved in the study.

The new findings, she said, have value as the field of cognitive science breaks free from old assumptions about evolution. Scientists have explained the history of species-specific variations in perception with differences in body size, brain mass, or the problematic notion that humans and primates evolved than other animals. “There is no way in nature to create a brain and a body around it,” says Herculano-Houzel. “There is no ideal brain. Not available better brain.”

Brosnan agrees with the findings of the Carnegie Mellon research group, which refutes old assumptions that primates have “better” cognition than birds or other vertebrates. “And in fact, if you look closely, even within the smaller taxa, there is quite a bit of variation,” she said. For example, gorillas perform trivial tasks, despite being great apes. For Brosnan, this suggests a need to study the cognitive abilities of less common species, such as reptiles. “What we’re seeing is that they’re really smart,” she said. “We just need to learn more about them.”

However, when it comes to estimating numbers, humans are the top performers. We can do that with about 10 percent accuracy. Cantlon suspects that the neural process is very similar for all species, but humans can only do it with a greater degree of sensitivity. It’s a skill that may have led to our ability to count — and perhaps the symbolic representation of numbers and letters.



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