People have long pondered what distinguishes humans from other animals. Over the years, philosophers have pointed to the ability to make and use tools, as well as the use of language. However, research has since shown that a variety of species use tools. For example, other primates have been observed using sticks to collect ants and termites and using stones to help crack nuts, and birds have been observed fashioning hooks out of wire to help them retrieve food. The question remains: Are advanced mental abilities—such as thinking and language—skills that are unique to humans?

While there is no doubt that animals communicate with one another, studies have yet to demonstrate a language among animals that is comparable to human language. Some animals have been taught to communicate with humans and seem to be able to understand words and communicate with sign language. Still, the question remains: Were these subjects really thinking symbolically or had they merely been trained by rote memorization? What appears to be communication could simply be mimicry and the result of conditioning by a reward system.

Recent studies have set out to observe whether nonhuman animals have the capacity for the abstract thinking that is the basis of language. For instance, chimpanzees and dolphins have demonstrated an understanding of grammar—depending on the order of words in the command, the animal was able to place or retrieve a specified object in a specified location.

The study presented in this video demonstrates that a sea lion has the ability to form logical relationships between symbols (such as sounds, letters, and numbers). For example, Rio has been taught that the sound of a telephone ring is equivalent to the letter "B" and also that all letters are equivalent to each other. When presented with a novel problem that she had not seen before, Rio is able to make the logical jump that the sound of the telephone (typically paired with the letter "B") could be paired with any other letter. In other words, Rio is able to figure out that if X=Y, and Y=Z, then X=Z. This type of logical conclusion demonstrates a thought process, not simply a behavior modified by training. This ability to recognize equivalence may be a precursor to language.

In the wild, such reasoning skills likely help sea lions make decisions critical to their survival. For example, by associating sights, sounds, and smells, sea lions can learn to keep track of various interactions, such as how to recognize friends and family members and avoid enemies and predators, and where to find food.

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