alt Hacker NewsI remember reading an article in National Geographic of how crow's brains are much more interconnected than is the norm in mammals, i.e. IIRC they have a higher density of synapses between neurons. From that article, it seems that the usual brain weight vs. body weight to determine intelligence, which seems can be used to approximate intelligence in different species of mammals, cannot be used for birds (or at least crows, which the article was focusing on).
In other words, they seem to achieve better results with smaller brains than we thought. And yes, crows (in EU) do exhibit some pretty intelligent behavior.
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I'm not an expert in the area but have read a bunch on this topic to try and understand it better. Bird brains and human brains are structured very differently. Birds are much more like GPUs with independent distributed processing happening in parallel. Mammals have these big bidirectional layers where signals are constantly propagating up and down in a big connected computation.
I wonder what the energy/evolutionary cost of densely-connected brains is. If it's advantageous, why are crows exceptional?
I've read there's also a social aspect - crows are extremely social creatures, as are humans, and other highly intelligent animals like whales. That does seem to be a common denominator.
Regarding that, I'm reminded of another story - on my daily walk near work, there was a dead crow on the pavement. 5 or so crows were standing all around it, doing nothing really. Even me passing close by did not trigger them to fly away or anything, it seemed like they were standing watch on the body. The next day, it was still there, same thing. The 3rd day, it was gone, but the crows were still standing watch in the same manner. I didn't know what to make of it other than it appeared they were mourning or taking part in some type of ingroup ritual. I didn't see it again after that, but it struck me.