Is it fairly settled in the scientific community that the physical size of a creature’s brain is indicative of its potential intelligence? I seem to recall references to the size of dolphins’ brains as an indication of their potential (human-like) intelligence, yet this article posits this ain’t necessarily so. Anyone have the straight dope?
Cheers!
BA
I seem to recall that there was also a link between intelligence and the number of wrinkles on a brain, but I can’t find a link (so maybe I have fewer wrinkles than I should…)
The structure of the brain is more important than its simple volume in determining the intelligence of the animal that possesses it. The thickness of the cerebral cortex, the amount of folding in the cortex, and the number of nerve connections in the brain, and the amount of energy used by the brain are all factors in determining actual intelligence. If it was simply about size, large cetaceans such as whales as well as elephants and large ruminants might be expected to be more intelligent than humans. But they have different brain structures than humans; essentially their brains aren’t as efficient for their size, just as a room-sized old computer wouldn’t be as efficient as a modern one.
That being said, there are times when cranial capacity is used as a measure of intelligence, such as when examining fossils of human ancestors. In these cases, we know something about the brains of our more distant ancestors (higher primates), and we know something about the human brain. We can safely assume that the brain structure of human ancestors would resemble something between that of the higher primates and that of modern humans. If a chimpanzee’s brain is already similar to a human’s with respect to cortex thickness, folds, and number of connections, we can then compare its size with that of a human’s. In this case, we see that brain size relative to body size increases as one gets closer to modern humans, and so we can assume that human ancestors became more intelligent as they evolved, though some individuals may have been more intelligent than others. Note that it would still be better to examine the actual brain in this situation, but that’s made impossible since the human ancestors being examined are extinct. In the absence of a living brain, cranial capacity becomes the best way of estimating intelligence.
Well, you run into the problem of defining “intelligence” right away. Intelligent like what? If you were suddenly stricken blind and had to catch and eat insects, a bat might think you are mighty stupid. (Yes, I know bats aren’t blind - trying to make a point.)
Speach and communication? There’s the African Grey Parrot (Alex is probably the most famous) who uses referential communication and has a vocabulary larger than many 3 year old humans. Tiny, tiny brain in a parrot.
Construction skills? Many insects are pretty darn smart builders as a collective, but hardly trainable as individuals.
Trainable? Rats are highly trainable, and used in lots of intelligence studies. A good lab rat is easily smarter than my dumb cat.
Problem solving? Meet the raven, a pesky bird who can undo just about any fastening device designed for opposable thumbs.
IIRC, Einstein had his brain removed after death so researchers could see what made it special. The organ itself was ordinary in mass and size. It was what he managed to do with it that was special.
I just know I’m going to win Übergeek of the year for this but the analogy isn’t entirely apt. The larger mammal brain should have, AFAIK, a proportionally larger number of neurons that are essentally the same size and work the same way as those in a smaller brain.
The large, inefficient computer is so because it has less complexity, fewer gates and registers than the modern, tiny one. The fact that it is larger is only because discreet parts are larger than those that do the same function on a microchip.
Actually, Einstein’s brain was ordinary in mass and size, as well as neuron density; however, he had 10 times as many glial cells as the average Joe.
Additionally, brain to bodymass weight ratio is important for deciding intelligance, as is the number of folds in the brain. In cases of very severe FAS, postmortum examination of the brain reveals an almost completely smooth surface.