For example, chimps and preschoolers could tell at a glance which dish contained a few more raisins. But when the dishes were covered and extra raisins dropped in, the apes kept better track of which dish had more.
Herrmann speculated that perhaps everyone starts out with ape-level math skills that humans surpass upon learning to count.
Then she tested social learning — communication, imitation and gauging intent from behavior. For example, Herrmann hid a treat under one of three cups and pointed to the right one. Preschoolers were much better at knowing to follow her gestures.
Overall, the preschoolers accomplished social-learning tasks correctly 74 percent of the time, while the apes did only 33 percent of the time.
Herrmann concluded that backs one theory of the evolution of human cognition that specialized social skills more than general intelligence explain why humans learn more, in complex cultural groups, than do other primates.
But to de Waal, the preschoolers just had to imitate another human to pass these tests, while the apes had to imitate a stranger of another species, a higher hurdle.
Herrmann chose orphaned apes raised around humans to minimize those concerns.
Other studies have found that chimps pass similar social-learning tests when they know the human tester well or when a fellow chimp is trained to administer the tests, which is the method Yerkes now uses.
Recall the trick tube that Herrmann's apes could not open right? De Waal trained two chimps from different families to open a trick box in different ways and then sent them home. Later, their relatives mostly opened the box the way their matriarch had been trained, similar to human cultural learning.
Social learning is "maybe not as a perfect as in humans, but it's very well-developed," de Waal said.
