If an elephant’s brain is bigger than ours, why are they not smarter?

Gary Meaney author of Zoology's Greatest Mystery (2022)Nov 2 If an elephant’s brain is bigger than ours, why are they not smarter? This is a good question, because the answer teaches us a lot about the nature of intelligence itself. The average human brain weighs about a kilogram and a half, which is remarkably small really. The sum of all consciousness is housed within that little scoop of nervous tissue. On the other hand, within the cranium of an African bush elephant sits a brain well over twice the size of ours. It’s clear that there’s more to intelligence than just brain size. The baleen whales of the oceans have brains weighing 7 kilograms, well over quadruple the mass of ours. However, their behaviour is much less complex and sophisticated than that of humans, or indeed of elephants. Baleen whales aren’t stupid - their songs are a rich and advanced form of communication, and they’ve been known to display altruism - but their intelligence definitely isn’t proportional to their massive brain size. This is of course because their brains are tiny relative to their bodies. A blue whale’s brain makes up as little as 0.005% of its total body mass! Our brains, by comparison, are about 2.5% of our bodyweight. So is brain-to-body mass ratio the true decider of intellect? It’s certainly a better metric to compare between animals, but still one which is deeply flawed. It turns out that, all else being equal, brain mass does not scale linearly with body mass. After all, there is a minimum number of neurons an animal needs to function, a concept known as the “grey floor”. Smaller animals tend to have much higher brain-to-body mass ratios, without necessarily seeming any more intelligent. A humble shrew, for example, has a brain which constitutes one tenth of the size of its body! If the metric were reliable, the shrew would be taming us! While we’re on the topic, I should mention that the species with the lowest brain-to-body mass ratio of all vertebrates on this Earth is the magnificently named bony-eared assfish. Brains consume huge amounts of precious energy, so in the incredibly barren environment of the deep sea, the bony-eared assfish has done away with most of its grey matter. For a fish with such an unflattering name, it is hauntingly beautiful! Anyway, it’s clear that raw brain-to-body mass ratio is far from a perfect measure of intelligence; it is too harsh on big animals, and too kind to small animals. Scientists have studied the relative brain sizes of mammals, and come up with a formula that adjusts for this problem. Applying this formula gives a new, more refined metric: encephalisation quotient, or EQ for short. In other words, EQ is the ratio of actual brain size to predicted brain size. When we compare different animals’ EQ values, the results line up a lot more with what we would expect, intelligence-wise. Humans have the highest score of any animal, at about 7.6. The tucuxi, a very interesting type of freshwater dolphin from the rivers of South America, takes second place. It measures only 1.5 metres in length, and has a bright pink underbelly! Manta rays have one of the highest EQs among fish, octopuses triumph among invertebrates, and corvids outperform their feathered friends. These results are all exactly what we would predict based on behavioural signs of intelligence. So, is encephalisation quotient really the answer? Probably not. Once again, this method seems to fall short of being perfect. On average, birds have much lower EQs than mammals, but there is ample evidence to suggest that birds are incredibly smart. In fact, all the dinosaurs, not just birds, have surprisingly low encephalisation values. If estimated EQ is to be believed, Tyrannosaurus rex was less intelligent than a slug. Believe it or not, the sauropod dinosaurs have the lowest score of any animal in history ever measured, at as low as 0.01! There are several likely reasons for this. The formula for encephalisation quotient was based only on data from mammalian species, so in general it probably shouldn’t be used to compare mammals to non-mammals. Bird/dinosaur cells are much smaller than mammalian cells. For its size, a typical avian brain has twice as many neurons as a standard mammal brain! Raw brain size, brain-to-body mass ratio, EQ… all these metrics share a fundamental problem: they’re all based on overall brain mass in some way, and there’s a lot of stuff inside brains that has nothing to do with intelligence. For example, a large portion of whales’ and dolphins’ brain mass is just insulating blubber! There are all kinds of factors like this that really muddy the waters. Perhaps it’s better to just focus on the part of the brain that actually does the thinking. The cerebral cortex is thought to be the seat of intelligence in mammals. This grooved and convoluted outer layer of tissue is responsible for processing our senses, finely controlling our movement, abstract thought, and much more. Non-mammal animals don’t have a cerebral cortex per se, but they always have an equivalent brain region - for example, birds have their dorsoventricular ridge, or DVR. So far, the single best predictor of intelligence we have found is the number of cortical neurons; that is, the total number of nerve cells within the cerebral cortex (or equivalent area). Humans have at least 16 billion, which is exceptional! Elephants, despite having a brain twice as large, have about a third as many cortical neurons. However, the real world champion is the orca, believe it or not, with an absolutely astonishing 43 billion cortical neurons! In fact, by this measure, humans sit at humble fifth place. There are four species of dolphins with more cortical neurons, the most of all belonging to the orca. Some might be quick to discredit this method as soon as they hear that it doesn’t put humans on top, and I would encourage those people to keep an open mind. If we’re so, so sure that orcas are less smart than us, perhaps we’re looking at intelligence in the wrong way. But that’s a more philosophical discussion for another answer. Anyway, for centuries, humans have been trying to put a number on intelligence, to find some way to quantify it. None of the metrics we’ve come up with are perfect, but for now, the best we have is the number of cortical neurons. It doubtless has its discrepancies, but overall it seems to be an extremely useful way of comparing animal acumen. So, going back to your question, if an elephant’s brain is bigger than ours, why isn’t it smarter? Because the size of a brain, as we’ve seen, has little to do with intelligence. Apologies if this answer was long-winded, though I think we visited some interesting places on our journey through animal minds! Thank you everyone for reading, I hope you enjoyed, and have a great day. 66.3K views4.5K upvotes79