Same-Different Conceptualization in Dogs (Canis familiaris)

Abstract concept formation was once thought to be a uniquely human ability. An increasing variety of nonhuman species have demonstrated aspects of this ability, however, suggesting that conceptualization is a widely shared aspect of cognition. The capacity to form a concept of same-different, in particular, has now been shown in pigeons, primates, bottlenose dolphins, sea lions, and more. Traditional methods of studying abstract concept formation include matching-to-sample (MTS), same/different (S/D), and relational-matching-to-sample tasks, tasks that typically require animals to discriminate sets of planar images. Some of these methods may actually test familiarity, memory, associative learning, or other phenomena rather than a concept of same-different. In the current study, we tested same-different concept formation in domestic dogs using a variation on the S/D task that required subjects to discriminate sets of three-dimensional objects. This method avoids some pitfalls of matching-to-sample and S/D tasks that use two-dimensional images and thousands of training trials. Dogs were able to learn to classify sets of objects as “same” and “different” and proved to be able to immediately transfer this ability to novel sets, including sets of only two objects. Domestic dogs are promising subjects for future studies of same-different conceptualization due to their widespread availability and willingness to work cooperatively with humans.