Feature

With their sleek bodies and special sensory abilities, dolphins do not seem to have much in common at first glance with humans and other primates. But research shows that, despite the obvious physiological differences, the two species may share key cognitive abilities, such as the capability to master a symbolic language, coordinate social behaviors and demonstrate an awareness of one's own actions, said University of Hawaii psychology professor Louis M. Herman, PhD, at APA's 2004 Annual Convention in Honolulu. Dolphins even surpass man's closest relative, the chimpanzee, when asked to spontaneously follow the commands of a televised trainer--a measure of their ability to understand abstraction, Herman added.

Beginning in the 1980s, Herman and his colleagues initiated an intensive training program with the dolphins, when the animals were about 2 years old. The dolphins rapidly mastered a vocabulary of hand signals related to objects such as "ball" and actions such as "spiral jump" and their combination into sentences. They even learned to interpret an inverse grammar, showing language aptitude similar to that of bonobo chimpanzees, reported Herman.

In this language, the five successive hand signals "left, basket, right, Frisbee, in" ask the dolphin to place the Frisbee on the right into the basket on the dolphin's left. To follow this command, dolphins must watch and process the entire "sentence" before taking action, Herman said. Dolphins responded correctly about 62 percent of the time--far above the chance level of 4 percent.

The dolphins also demonstrated an ability to coordinate social behavior--which Herman illustrated through videos. First, the researchers trained a pair of animals to perform simultaneous behaviors in response to the sign "tandem." For example, the signs "tandem, jump" would ask a pair of dolphins to leap out of the water next to each other and at the same time--a common behavior in the wild. The trainers then taught the dolphins to respond to the sign "create" by rewarding them only when they perform a novel behavior in response to the sign.

In the video, Herman asked two trained dolphins to make up a behavior and perform it simultaneously--a command communicated by the signal "tandem, create." The pair of animals then dove down, apparently conferred and leapt from the pool together, spitting water from their mouths.

"Some planning must be involved in this," said Herman. "In order to spit water into air, some water must be taken in while underwater. We looked at this type of coordination in various ways, and we are still not sure how the dolphins do this."

It may involve mimicry, he said, as dolphins are unsurpassed in imitative abilities among nonhuman animals.

Herman's dolphins understood the "tandem, create" sign the first time they encountered it, and they also spontaneously followed the hand signals of a televised trainer--something that great apes can do only after extensive training. Comprehending the directions given by a flickering image of a trainer, as opposed to those conveyed by a three-dimensional, real-world trainer, takes an appreciation of abstraction, said Herman. The dolphins even correctly interpreted signals given by white dots against a black background, tracing gestures usually given by a trainer's hands.

The similarities in dolphin and chimpanzee intelligence observed in his and others' labs may shed light on what environmental conditions might favor the evolution of intelligence, said Herman. Perhaps it takes abilities such as social knowledge, communication, language use and abstraction to successfully navigate the complex societies characteristic of both of these animals, as well as humans, he said.

Further Reading

  • Herman, L.M. (2002). Exploring the cognitive world of the bottlenosed dolphin. In M. Bekoff, C. Allen & G. Burghardt (Eds.), The cognitive animal: Empirical and theoretical perspectives on animal cognition (pp. 275-283). Cambridge, MA: MIT Press.