New research suggests that 3-month-old human babies can use lemur calls as teaching aids. The findings hint at a deep biological connection between language and learning. But not everyone agrees that the new work shows that primate sounds can stimulate a child's linguistic instinct. "This work tells us that sounds that are more like human language are more effective," says , a psychologist at the University of California, Davis. "What is more controversial is why they are effective." She says it's still unclear whether the primate sounds are stimulating some deep linguistic circuit in the brain or just getting the babies to look.