Science Daily, February 2, 2009

Orphaned chimpanzee infants given special 'mothering' by humans are more advanced than the average child at nine months of age.

In the first study to examine the effect of different types of care for infant chimpanzees on cognition, researchers found chimpanzees who were given extra emotionally-based care were more cognitively advanced than human infants.

more at:

http://www.sciencedaily.com/releases/2009/02/090202140437.htm