A very common internet query is as to a list of the most intelligent animals. One might expect that this should have an easy answer, given that so much psychometric work has been performed on so many groups, much of it being of very similar type. One problem is that those tests that may be freely compared have not always been performed in the same manner, forcing us to rely on a limited subset of that data, and not every test provides a cognitive ranking in the same order. First and formost we must decide whether a universal g-factor even exists outside the primates. I believe that the first test that could apply directly to that question was run last year, and was consistent with there being such a universal g. Let’s then say there is and, consequently, all animals can, in principle, be uniquely ordered according to their intelligence.
Internet attempts to produce such a list always seem to fudge it with generalities, for example all octopuses might be taken as one animal even though they constitute an entire order, but chimps and bonobos might be two different animals on that same list, even though they are from the same genus. To remove that inconsistency I will use genus, eg making Human = Cro-Magnon +Neanderthal. I will assess each genus by their most intelligent extant species.
In order to get a rough metric of intelligence, I will use the number of billion neurons in the neocortex, divided by two if the animal sleeps unihemispherically (I abbreviate this measure as ‘b’). If the values are estimated by brain size I put the figures in brackets. Note, since these figures are calculated separately, they will not always match the order given for cognitive ability exactly.
1 Sperm whales (100 ± 50)b. The most intelligent animal on Earth by every metric I can find except tool use. Only K selection has sufficiently ambiguous results by which we might exceed them by a second metric. It might be said that we have the higher linguistic ability, but this is just an assumption. By measure, they have a larger vocabulary than humans, but human scientists have never bothered to test sperm whale social vocalisations for syntax, nor test its entropy.
2 Humans 19b.. These animals take tool usage to the next level. So superb is their ability to make and use tools, that was this the only metric of intelligence they would rank 1 on this list by a long chalk. In addition, humans are one of only two species in which their culture is sufficiently complex as for it to trump genetics as a predictor of reproductive success. Also significant is the human footprint as a metric of extelligence. Those measures, and many others, elevate humans and sperm whales well above the other animals on this list.
3 Killer whales (30 ±15)b. Widely guessed to be the most intelligent of cetaceans, until it was shown that sperm whales scored higher by every metric formally thought as uniquely elevated in this species. Also, bottlenose dolphins outdo them in tool use. Have the second most complex hunting strategies ever observed next to humans ( sperm whales hunt a quarter mile below the surface, and their actions have not yet been glimpsed by us – even once)
4 Pilot Whales 18b. Are here because of their very high neocortex neuron count. Have been trained by military and, in a few cases, for display, yet we have limited data on their intelligence. By anecdote, their ability to be trained is thought similar to the bottlenose dolphin, but it would now seem likely that their intelligence is of a significantly higher level. More work must be done.
5 Humpback Whales (20 ±10)b. Compose the most complex and longest non-human songs known. They also show the most easily recognisable signs of culture among cetaceans. Have several times been observed displaying interspecies altruism, a rare trait that may indicate elements of a high order of moral code.
CONTINUE to see the second half of the list.