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A study by Institute of Cognitive Sciences and Technologies, Italy shows that animals can use and comprehend symbols.

The research presents evidence of symbolic reasoning in tufted capuchin monkeys (Cebus apella), a South-American species that live together in groups of 6 to 40 members.

In the absence of language, the comprehension of symbols is difficult to demonstrate. Tokens can be considered symbols since they arbitrarily stand for something else without having any iconic relation to their referent. Researchers assessed whether capuchin monkeys can use tokens as symbols to represent and combine quantities.

In the experiment, five captive-born capuchin monkeys were individually tested. Each subject was presented with a “choice apparatus”, constituted by a platform with two sliding trays where different quantities of food or tokens were available.

This photo depicts Robot, a male capuchin, who has just selected three black plastic tokens (each corresponding to one piece of dried apricot, food C) preferring them to one brass hook (corresponding to one cheerios, food A). Robot is exchanging the first plastic token for one piece of dried apricot.
Credit: Institute of Cognitive Sciences and Technologies, Italy.

Each monkey chose between three different foods (conventionally referred to A, B and C), offered in variable amounts. Choices were made in two different contexts as follows:

• In the “real” context, monkeys chose between the actual foods.
• In the “symbolic” context, monkeys chose between “tokens” that represented the actual foods.

After choosing one of the two token options, monkeys could exchange their token with the corresponding food.

It was revealed that when one token B was presented against one to five tokens A, four out of ten capuchins relied on a flexible strategy that allowed to maximize their pay-off, i.e. they preferred one token B against one and two tokens A, and they preferred four or five tokens A against one token B.

Moreover, when two tokens B were presented against three to six tokens A, two out of six capuchins performed summation over representation of quantities. These findings suggest that capuchins can use tokens as symbols to flexibly combine quantities.

In short, though capuchins may not achieve adult-human-like symbolic competence, this study demonstrates that animal species relatively distant from humans have undertaken the path of symbolic use and understanding. It seems there is a continuum of language capabilities across species.