Originally posted by twhitehead
Dolphins are most definitely not as intelligent as humans. If they were, they could learn to our language and to read etc. Even if there are barriers to learning such as poor eyesight, different hearing range etc, they would do better than they currently do if they had intelligence equivalent to a humans.
I believe chimps can learn sign language and ha ...[text shortened]... even language would still show a greater level of intelligence than any other animal does today.
Sorry to glom onto your post, but just read the thread....
The mirror rouge test is not a test of intelligence, but simply a test of self-awareness. Self-awareness and intelligence could be orthogonal, they don't have to correlate with one another. Certainly testing one does not test the other though. As someone else pointed out, children under 2 often fail on the mirror self-recognition test, but we would be hard pushed to define them as unintelligent. Intelligence, as measured by humans, as at least two domain-general components, fluid and crystallized intelligence. Fluid intelligence is roughly the same as problem-solving, crystallized is roughly the same as knowledge. To say that the child failing the rouge test is not intelligent is not really correct, it just means they haven't yet acquired the knowledge to represent themselves in the mirror. A cat on the other hand, will never pass the rouge test, suggesting they lack the fluid intelligence to solve the problem.
People talk about animal (dolphin) intelligence as if humans should be arrogant to presume superiority, but seriously? Humans may be fraught with flaws of character and iniquity and downright chauvinism, but they clearly are the intellectual superior of the dolphin. The fact that you can understand the concepts I'm referring to, in a way that makes sense to you, and that I can predict with 100% accuracy that you will, all by looking at tiny arbitrary markings on a shimmering glass screen separated by perhaps thousands of miles and also by days, might give you an idea of the gulf between human and animal intelligence.
Finally - someone mentioned brain size and ratio of brain to weight. Neither of these metrics are particularly useful to compare across species. What is most important is the number of connections between neurons present within the brain. The greater the number of connections, the greater the number of folds within the cortex, the greater geometric complexity of the brain. The relative decrease in 'smoothness' of the cortical surface when we compare brains from rodents, to apes, to humans, etc gives a clue to the complexity of computations each species is a) able to carry out, and b) hence was designed to perform. Rats don't need to figure out how to speak, represent long-term episodic memories of multiple interactions with conspecifics, decide when, how and who to deceive, and so they don't have an evolutionarily and energetically expensive super-folded cortex. It's simply not worth the cost. Humans, on the other hand, need to function successfully in groups of other humans who are devious, deceiving and have very long memories. Success on that scales needs a serious amount of memory and computational power. Hence our elaborately folded, complex cortices with a recent estimate of 1.5 * 10^14 connections (Pakkenberg et al., 2003, Experimental Gerontology). That's a lot.