Western lowland gorillas' cognitive abilities and responses decline with age in ways that mirror human patterns, according to a study in the September issue of APA's Journal of Comparative Psychology (Vol. 119, No. 3).
For example, adult gorillas in their 30s or 40s can process small quantities of information, like deciding which stack is the larger of two, at a similar level to younger gorillas, but they need more time to do so. Moreover, as the size of the information increases, older gorillas' ability to process it decreases--a trend in cognitive processing that's also evident in research on people.
The study extends previous research that has not distinguished between the ages of nonhuman primates when comparing their cognitive-processing skills, says lead researcher and graduate student Ursula Anderson, of the Georgia Institute of Technology and research associate at Zoo Atlanta.
"It's important to look at the age of nonhuman primates because when we compare them to humans, there are possible age differences among both groups," Anderson says.
To reach the study's findings, Anderson and her colleagues trained 11 Western lowland gorillas--six that were between 37 and 43 years old and five that were between 6 and 13--to select which of two plastic trays held more pieces of cereal or grapes.
In the first experiment, both the groups of gorillas selected the larger quantity more frequently than chance would predict, and the younger gorillas responded well over a minute faster than the older gorillas.
In a follow-up study, the gorillas completed the same task, only without prior training and with larger quantities of cereal and grapes grouped in the same tray. In addition to being slower to choose a tray, older gorillas chose the larger number of items less often than did younger gorillas.
Such results not only can lend insight into human cognitive decline but can enhance zoo workers' ability to care for gorillas, says study co-researcher Mollie Bloomsmith, PhD, associate director for the Center for Conservation and Behavior at the Georgia Institute of Technology and head of behavioral management at the Yerkes National Primate Research Center at Emory University.
"The better we can understand these animals, the better we'll be able to care for them," Bloomsmith says.
In the future, Anderson and Bloomsmith aim to continue comparing cognitive abilities in apes and contrasting those results with findings in humans.