Orphaned infant chimpanzees that received attentive, nurturing care from human surrogate mothers were found to be more intellectually advanced than the average human baby when both groups were compared at the age of nine months, according to a new study published in the latest issue of Developmental Psychobiology.
The authors believe the study is the first to ever examine how different types of human care can affect the cognitive development and overall well being of infant chimpanzees.
"The early rearing environment is incredibly important for chimpanzee infants as it is for humans," co-author Kim Bard told Discovery News.
Bard, a professor of comparative developmental psychology at the University of Portsmouth, conducted the research with colleagues Marinus van Ijzendoorn, Marian Bakermans-Kranenburg and Krisztina Ivan.
The chimpanzee participants consisted of 46 male and female orphan infants that received either standard or responsive care from human surrogate mothers. Standard care met food and health needs, but provided no additional social and emotional nurturing from the caretakers, although the chimps had access to their primate peers.
Responsive care involved daily four-hour-long mom sessions, where the humans would play with the infant chimps, encouraging their motor development and communication skills while helping them to meet new challenges with curiosity instead of distress.
When the chimps were nine months old, they took an IQ test normally used to evaluate human infant development. Bard explained that typical items on the cognitive test required the chimps to "imitate scribbling on paper," look at pictures in a book as the examiner pointed to each one, and pick up a cup to find a block hidden underneath.
The infant chimps aced the test, even surpassing the scores of average human infants tested at the same age.
Follow-up studies on the chimpanzees are planned, but comparisons between humans and chimpanzees at later ages are complicated by the fact that the two primates interact with themselves and the world in different ways. Humans also define intelligence with our particular abilities as the yardstick.
"There are many domains of development, such as emotional, social, cognitive, communicative and motoric," Bard said. "Because of the differences in rearing or even cultural experiences, in interaction with development among these domains, it is difficult to pinpoint ages when 'the typical human' surpasses 'the typical chimpanzee.'"
She added, "Clearly the extensive linguistic ability of humans, and their ability to construct complex objects, such as the computer I'm using now, are beyond the capacity of chimpanzees."
Lisa Newbern of the Yerkes National Primate Research Center informed Discovery News that the chimpanzees were tested there, but only up until 1995, when the Yerkes Great Ape Nursery Closed.
"The NIH (National Institutes of Health) issued a breeding moratorium on chimpanzees that same year," Newbern said.
Bates explained that the current study "required extensive microanalysis and collaborative efforts" that resulted in the new paper.
Bates and her colleagues hope that conservation of African rainforests, along with "providing the best possible conditions" for chimpanzees at zoos and other places, will help them "to flourish in many different settings."
Van Ijzendoorn added that other studies on human babies suggest they can also excel or decline depending on the care they receive at this critical time of early life.
"At the moment, hundreds of thousands of orphans — either social orphans abandoned by their parents or orphans who lost their parents because of AIDS (and other reasons) — are raised in orphanages in Eastern European countries, Africa, China, India and elsewhere," he said, concluding that "enrichment of the environment in the orphanages can make a big difference in cognitive development, and we think also for emotional development."