In the learning test, however, guinea pigs had cavies beat. Compared with cavies, the guinea pigs more quickly grasped how to knock over plastic cylinders to get bits of cucumber as rewards. That's unexpected, the scientists say, in light of evidence that domestication, broadly speaking, produces less-intelligent animals. Rather than experiencing cognitive decline, these fuzzy pets "might be simply better adapted to the testing procedure," the authors write, able to learn quicker than your average cavy in a man-made environment.
Several studies point out that wolves (and dingoes) are superior to pet dogs at tests of logic and social intelligence. Domestication seems to lead to smaller brain sizes, too (though brain size is an imperfect measure of intelligence). Guinea pigs, for example, have brains about 13 percent smaller than those of similarly-sized cavies. Despite their smaller brains, guinea pigs, at least, seem to have escaped the trap of dumb domestication.