Dolphins and Episodic Memory
Humans use episodic memory to mentally revisit personal experiences, and new evidence suggests that dolphins may share this ability. Long believed to be a uniquely human trait, episodic-like memory has also been demonstrated in rodents, birds, and cephalopods. Findings published in Current Biology now add bottlenosed dolphins (Tursiops truncatus) to this growing list of animals.
Designing a Memory Test for Dolphins
Researchers led by James Davies at the University of Cambridge created a clever experiment to determine whether dolphins could recall seemingly irrelevant details of past events. The test relied on “incidental encoding followed by an unexpected question,” a method considered one of the strongest approaches to probing episodic-like memory in animals.
The “Where” and “Who” Trials
Eight dolphins were trained to fetch a ball from a person holding it. During training, both the ball’s location and the identity of the person varied, making those details irrelevant. Later, during the trials, the ball was hidden behind someone’s back:
- Where trials: The ball was hidden in the same spot as before, but with different people.
- Who trials: The ball remained with the same person, but the location changed.
The results were striking. All dolphins succeeded in the “where” task, and seven out of eight also passed the “who” test, indicating that they recalled past details that had not been directly emphasized during training.
Expert Perspectives
Indiana University psychologist Jonathon Crystal praised the design as compelling evidence of episodic-like memory in dolphins. The use of incidental details and unexpected questions makes it unlikely that simple familiarity or short-term memory explained the results.
Kelly Jaakkola of the Dolphin Research Center highlighted the study’s innovation, noting that it allowed dolphins to demonstrate memory recall without prior training. She did caution that experiments were not perfectly blinded, leaving a small chance of unintentional human cues. However, she emphasized that the team took steps to minimize this risk.
Why It Matters
These findings support the idea that dolphins, already known for their intelligence and social complexity, possess sophisticated memory abilities comparable to those of other cognitively advanced animals. Davies notes that the controlled setup made it unlikely that dolphins relied on unconscious human cues.
Implications for Animal Cognition
The study adds momentum to the view that episodic-like memory is more widespread in the animal kingdom than once thought. It also raises intriguing questions: Which animals have this capacity, which do not, and what traits set them apart? As Jaakkola observes, uncovering these patterns will be “the fun part of the game” in understanding animal cognition.
