Research Explores What Dolphins Understand about Hidden Objects
Grassy Key… The scientific journal Animal Cognition has published Dolphin Research Center’s latest research paper on What Do Dolphins (Tursiops truncatus) Understand About Hidden Objects. The ability to reason about objects that have disappeared from view, which is known as object permanence, has been studied in many terrestrial mammals, but the DRC study is the first to explore this with marine mammals.
“When you show an object to a human infant who’s only a few months old and then hide it, as far as the baby is concerned, the object ceases to exist. It’s truly “out of sight, out of mind,” explains Research Director Dr. Kelly Jaakkola. “When humans are around 12 months old, they realize that the object still exists and search for it even if they can’t see it.”
For this study, DRC’s researchers showed a number of dolphins a plush toy alligator, and then hid the toy in one of three containers while the dolphins watched. Scientists call this condition “visible displacement”. They then asked the animals to choose the container holding the alligator. The dolphins chose correctly with a high rate of accuracy.
Several other non-human species have demonstrated this ability, including gorillas, chimpanzees, parrots and dogs. DRC then explored a harder condition called “invisible displacement”. They again showed dolphins the plush alligator, but then put the toy in a cylinder. They placed the cylinder in the container and then transferred the alligator out of the cylinder when the dolphin could not see this action take place. Apes are the only mammals besides humans that demonstrate they can solve these kinds of trials. Since apes, humans and dolphins share other specific skills – including mirror self-recognition, ability to imitate, and symbol recognition – DRC’s scientists fully expected that dolphins would also succeed with invisible displacement, but they didn’t.
“Scientifically, we were quite surprised to realize that dolphins could not solve invisible displacement trials,” Jaakkola says. The reasons why remain unknown. “There are many possibilities. They might lack an understanding of containment since containers as we understand them do not exist in the sea. In their underwater world, dolphins also use echolocation, which is their natural sonar. If a fish disappears beneath the sand, for example, dolphins can echolocate and still know where the fish is located. So, perhaps, they just don’t need this ability in the first place. Further research could address this puzzle.”
Even though the dolphins did not demonstrate the ability they expected, DRC’s research team is anything but disappointed. “Our studies are helping to build a more complete picture of dolphin cognition,” Jaakkola adds. “To do that, it’s just as important and fascinating to figure out what they can’t do as well as what they can so that we can really begin to understand how they think and learn.”
For over 25 years, Dolphin Research Center has dedicated itself to learning more about marine mammals and then sharing that information with the world. The nonprofit education and research facility is home to a family of Atlantic bottlenose dolphins and California sea lions. Open daily to the public, DRC features narrated behavior sessions and educational presentations throughout the day, as well as a variety of interactive programs and other educational programs. For more information about the center, visit www.dolphins.org or call 305-289-1121.
