Chimpanzees and two-year-old children are as clever as each other but dogs are not as smart as previously thought, according to a University of Queensland study.
Recent School of Psychology PhD graduate Dr Emma Collier-Baker added tighter controls to a famous logic experiment in which a desired object – food or a toy – is transferred from a small container into one of three boxes.
Subjects then try to identify the box containing the object by pointing at it or walking over to it. This invisible displacement task, devised by developmental psychologist Jean Piaget in the 1930s, tests the ability to “think” about an object that is not visible.
Several decades of research have revealed that great apes (including chimpanzees) performed the task as well as two-year-old children while other animals such as monkeys, dolphins and cats consistently failed the task.
“Dogs were a surprising exception, repeatedly passing the task in several studies in the 1990s. However, our study – involving 35 dogs of various breeds – showed they were using other simple cues to find the object and not ‘thinking' or using logic after all,” Dr Collier-Baker said.
“By introducing a range of more stringent controls to the experiment, we showed dogs had effectively been ‘cheating' to pass the test and were simply going to the box closest to the small container.
“In contrast, 21 two-year-old children, tested with identical apparatus to the dogs, were able to pass the task no matter what the proximity of the small container to the target box.”
This finding threatened the validity of studies with other species which also lacked these control conditions. Therefore, Dr Collier-Baker went on to test two chimpanzees sourced from Rockhampton Botanical Gardens and Zoo, four gibbons (siamangs) from Adelaide Zoo, and a spider monkey from Alma Park Zoo.
The desired object was food such as grapes or dried pawpaw for the apes, siamangs and monkeys, a tennis ball for the dogs and a small toy ball for the toddlers.
Unlike dogs, chimpanzees continued to find the hidden object under all control conditions, performing like two-year-old children on the task. The spider monkey failed the task, while the performance of siamangs was mixed and Dr Collier-Baker is currently following this up.
Her findings on dogs were published in an article in the prestigious Journal of Comparative Psychology with her colleagues Joanne Davis and Dr Thomas Suddendorf, also her thesis supervisor and School of Psychology Associate Professor.
The article was awarded the 2004 Frank A. Beach Comparative Psychology Award by the Division 6 Awards Committee of the American Psychological Society for the best paper published in the Journal that year.
The chimpanzee study was published in Animal Cognition with her colleagues Joanne Davis, Dr Mark Nielsen, and Dr Thomas Suddendorf. Following on from this study, Dr Collier-Baker and Dr Thomas Suddendorf tested chimpanzees and children on a more complex invisible displacement task which they had been unable to solve in previous studies. Dr Collier-Baker designed a novel testing format for the task which found chimpanzees and children passing the task.
These results complement a growing body of evidence for shared representational capacities in great apes and two-year-old children. The study has also contributed new testing methodology to the literature and has been published in the Journal of Comparative Psychology.
Dr Collier-Baker, now a postdoctoral research fellow at UQ, said she was continuing her research on gibbons.
“Gibbons are lesser apes and these primates have been surprisingly under-studied despite their value for reconstructing the evolution of primate cognition,” she said.
“Almost nothing is known about the cognition of these apes so my PhD and ongoing studies with Dr Thomas Suddendorf are important inroads to gaining knowledge about them.”
Her PhD findings will also contribute to the development of enrichment objects and devices to improve the quality of life for captive primates as well as reinforce the importance of global conservation efforts of apes.
Source: University of Queensland