Thursday, October 13, 2011


kw: observations, intelligence

This chart, available from many sources, shows the brain-versus-body size and the Encephalization Quotent (EQ) for a number vertebrates. These are averages, so you can imagine each dot to represent a small cloud of points. The bold line marked "Higher vertebrates" shows the trend for mammals and birds, while the one for "Lower vertebrates shows the trend for reptiles, amphibians and fish.

The bold lines have a slope of 2/3 (in logarithmic terms), and are the scaling axes for EQ as a rough measure of relative intelligence. The upper line is drawn such that a 4 kg house cat would fall on the line, and is defined as the EQ = 1.0 line. The lower line is the EQ = 0.1 line. By proportion, you can see that humans, whose dot is near top center, are somewhat less than EQ = 10, and in fact if you use the formula shown along the line, an average person would have an EQ of about 7 to 7.5.

Just to the right of that point, "Porpoise" represents the bottlenose dolphin, which has an EQ in the range 4-5, making it the "brainiest" sea creature. I read somewhere that an octopus, I don't know which species, has an EQ around 3 or 4, but their brain is so much differently organized than the vertebrate brain—for one thing, it is ring shaped—that the measure may not be a meaningful comparison.

I don't know whether EQ truly correlates well with "intelligence". For one thing, we don't yet have a good definition of intelligence. But it is known to correlate well with the amount of time young animals spend playing. Humans of all ages, dolphins of all ages, and the young of elephants, octopi, dogs, cats (and many adult dogs and cats), and many kinds of birds have been observed playing. Even mice play. I haven't read whether fish or reptiles play. Maybe somewhere around EQ = 0.25 is a threshold below which play is not found.

Apparently, somewhere near EQ = 0.05 is a threshold of the amount of brain needed to keep a vertebrate body from dying outright. A bigger brain than this has added abilities to modify the environment (such as by building a nest) and conduct social interactions. The more "extra" brain there is, the more capable such functions become. I suppose. I am still waiting for a more clear answer about the amount of brain, either absolute or relative to body size, needed to form a self-concept and self-consciousness. The early hints are that it is near EQ = 2, where Chimps are found. Once we learn more, lots more, about natural intelligence, I hope we'll also be able to produce machine intelligences, or at least to know what it would take (IBM's Watson is still a far cry from a robust machine intelligence, and it is a multi-million-dollar stack of computers and databases the size of a bedroom).

I suspect the threshold of language is near EQ = 3, maybe less, so our efforts to communicate with dolphins (so far with poor success) make it clear that, if SETI ever does detect the radio broadcasts of space alien civilizations, we'll be in for a long, long learning process to figure out how to understand what they are saying.

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