Rod Bastanmehr at AlterNet writes: “Are Humans Inadvertently Helping Make Animals Smarter?” It’s a summary of work that shows larger brain sizes among wild animals living in cities and in proximity to humans:
Dr. Snell-Rood studied dozens of individual animal skulls, some as old as a century, from ten different species including bats, gophers and mice. In two of the species, the white-footed mouse and the meadow role, the brains of the animals plucked from metropolitan areas or suburbs were about 6% bigger than those of the animals taken from farms or other rural areas. Dr. Snell-Rood's hypothesis after assessing the first wave of results was that brains become significantly bigger when they move to cities or bustling towns, where the animals must learn to find food in places that they're not biologically trained to encounter or expect.
He doesn’t describe the other side of this: Domesticated animals have generally evolved smaller brains than their wild ancestor species.