It has been found that chimpanzees, gorillas and orangutans can represent words and communicate with one another.
Chantek, an orangutan, was trained to use sign language. Chantek learned 140 signs, and made some up himself.
Orangutan abilities have been historically underestimated.
Chantek was raised with a human culture, and taught signs from American Sign Language. The signs were given in english word order, or pidgin Sign English.
Chantek was not exposed to speech for the first several years, but then was.
Chantek was first taught signs by molding, but later by imitation.
Signs were considered an active part of the vocabulary when he used
them spontaneously and appropriately on half the days of a given month.
Most signs (127) reached this level. This was a compromise between the
liberal Terrace et al. (1979) spont. use on 5 consecutive days and the
conservative Gardner and Gardner (1969) spont. and appropriate use on 15
The first signs occurred after one month of enculturation: "food eat" and "drink".
During the study period, he used 1/3 to 1/2 of his signs every day.
Only 22.7% of his signs were to try to get food and drink.
Signs Chantek knew:
Like children, Chantek prefers to use a name rather than a pronoun, as the reference is fixed-- even when talking to that person.
Conversations muset have little imitation and lots of spontinaity.
for example, at 26 months, for Nim (A chimp in another research lab) and Chantek:
|interrputions of caregiver||35%||8%|
|interruptions of ape||~18%||9%|
Chantel had some interesting grammar. When the object referred to was present, then the form that of an utterance would be object-GIVE, but when the object was not present, then the form would be GIVE-object.
Representations must have at least these things:
The Protodeclarative Stage (has 4 substages)
Chantek began to use attributes: "Red bird" and "white
cheese food eat."
You can find out what an ape means when a sign is used by looking at the context in which the sign was used.
Results of studies of this sort show that most of Chantek's signs came to mean the normal adult meanings.
Chantek overgeneralized in interesting ways, too. For example, he used the sign "lyn" for all caregivers, but never to strangers.
Chantek used to use the word "dirty" to refer to bad things, until he learned the word for bad. Then he started using bad, and dirty changed its meaning to be more like the real meaning.
He used "open" to mean moving large objects. There
are several other examples of overgeneralization.
Referring to things that are not present is called "displacement." Chantek did this often. At 8 years of age, 38% of his signings showed displacement.
p529. Deception is also an important part of language development. Chantek made about three deceptions per week. There are some interesting examples in the paper.
p530. Though he wasn't taught to do it, sometimes Chantek would sign with his feet. This is evidence for a mental representation of an image of signs. Chantek had a strong left hand bias in signing.
p531. Chantek's freestyle drawings resembled those of a three year old.
p532. Chantek was given a series of cognitive tests. On one of them, at age 4.5 he scored like an 18-24 month old human.
p533: Language tests such as Miller's suggest that Chantek
had entered Piaget's sensorimotor stage. There is some evidence
that he entered the preoperational stage.