Human Children Learn Language: Do Apes?

Tomasello, M., Call, J., and Gluckman, A. (1997). Comprehension of novel communicative signs by apes and human children. Child Development, 68, 1067-1080.

Overview:

Communication Versus Communicative Intent

What really is language? Certainly there is a communication aspect; individuals engage in some sort of behavior, such as gesturing or speaking, in order to convey information. Young children learn gestures and words very quickly. Language also involves a communication intention; individuals with language recognize that others are purposely trying to convey some sort of information. This communication intention allows even very young children to immediately comprehend and helps them learn to imitate new gestures or words.

Apes, such as chimpanzees and orangutans, living in a human-like environment, can learn communication signs and symbols. For example, Washoe, raised by Allen and Beatrix Gardner, learned American Sign Language signs and grammar. Kanzi, a chimpanzee trained by Dr. Sue Savage-Rumbaugh of Georgia State University, has learned to communicate with the use of a computer symbol keyboard.

The slow progress that apes make in learning signs and symbols brings into question whether they are learning language or a very sophisticated type of discrimination task. If apes are capable of language, they must recognize communication intentions as well. Tomasello, Call, and Gluckman (1997) were interested in whether apes do recognize communication intention. They compared performance by young children and apes on a communication game.

Article Summary

An important feature of human language is communicative intent. People learn new language signs and symbols (these include spoken words, gestures, physical symbols such as writing) because they recognize that other people are attempting to communicate something to them. For example, pointing a finger at an object has no intrinsic meaning in and of itself, but infants quickly discover that pointing means "Look over there."

Our closest relatives, the apes, do not appear to use signs or symbols in their everyday interactions with others of their species, yet a number of apes have been taught rudiments of language. Do apes understand communicative intent? This is the question Tomasello and his students addressed.

Tomasello, Call, and Gluckman compared how toddlers and apes responded to a variety of communicative signs. They hypothesized that if an individual understood the communicative intent of some sign (such as pointing or displaying some other form of behavior), the individual, ape or child, would quickly recognize the relevance of the sign. Thus, the second encounter of the sign would lead to immediate comprehension of its meaning. However, if the individual, ape or child, did not recognize the communicative intent of some sign, the individual would have to learn the relationship between the sign and it's meaning as a discrimination task. This learning would take a number of trials of pairing the sign with the meaning.

Toddlers, aged 2 1/2 and 3 years old, were first taught how to find a hidden reward (a sticker). Then, the reward was hidden and one of three signs was used to indicate where the reward was hidden:

• The experimenter pointed to the container in which the reward was hidden.
• The experimenter placed a marker, consisting of a small wooden block, on the container in which the reward was hidden.
• The experimenter held up a replica of the container in which the reward was hidden.

Needless to say, the children quickly discovered the intent of each sign. Pointing was more easily and quickly understood than the marker or the replica, but even the replica was understood by many of the children.

Chimpanzees (some who had been trained to use the marker as an indicator of food) and orangutans (all of whom had learned the marker and one who had learned about pointing) participated in the same tasks as the children. The apes received a food reward rather than a sticker, however.

Unlike the children, even after many trials with the signs, the apes did not learn to respond to any sign they had not already learned. The chimpanzees who had not learned about the marker did not learn to find the reward based on the marker sign. Only the orangutan, Chantek, who knew about pointing, was able to use pointing to reliably find the food reward. Thus, Tomasello et al. found no evidence that any one of the apes discovered the communicative intent of any of the three signs.

Tomasello and his students concluded that the apes did not understand the communicative intent of the signs and would have to learn them as discriminative stimuli. Based on naturalistic observation, they also concluded that ape communication in a natural environment doesn't have communicative intent.

Instead, ape communication appears to result from repeatedly paired behaviors. Tomasello et al. described how communication between a mother and her infant might develop: The infant wants to climb on the mother's back for transportation and comfort. The infant pushes down on the mother's back so it can crawl up. Eventually the mother learns that the push indicates the infant is about to crawl on her back and begins to crouch down as soon at the infant places its hand on her back. Ritualized behaviors like this don't require communicative intent but could be the evolutionary precursors to language. True language, then, may have evolved when early humans recognized that their communicative partners were intending to communicate information.

For Instructors

Links to the Lecture

WNET, a PBS station in New York, has developed a series called The Mind. Part 7: Language considers language from a biological, evolutionary, and developmental perspective. It provides a good link to the research article and a jumping off point for a discussion about human versus nonhuman language.

The Mind: Part 7: Language (1988, WNET/New York, 60 Min.).

Discuss the findings of Tomasello et al. in the context of the findings by Gannon, Holloway, Broadfield, and Braun (1998) of asymmetry of the planum temporale in chimpanzee brains.

For Students

About the Authors

Michael Tomasello is a developmental psychologist at Emory who also works with the Anthropology department at Emory University in Atlanta, Georgia, and the Yerkes Regional Primate Research Center affiliated with Emory University.

About the Journal

Child Development publishes a wide range of articles dealing with development from the prenatal period through adolescence. Check out some of the selection in recent Tables of Contents.

Links to Life

This is an ABC News article about Chantek, one of the participants in this study. Chanteck can sign a lot of words and makes unique combinations of words but does he have language? Kanzi learned his first symbols from his mother who was taught to use a computer keyboard with symbols on it for communication. Here is a New Scientist article about nonhuman language that features Kanzi and his trainer Dr. Sue Savage-Rumbaugh.

TIPS is a computer language program. Have a conversation with the computer. Is this language?