The subjects of the program, nine chimpanzees, were reared in a laboratory environment specifically designed to stimulate their intellect, as animals raised otherwise fail to thrive.
This was in contrast to the traditional psychology lab where the animals are caged and remain in solitude.
Jessie, Sadie, Bert, and Luvie, 1975 controls, were not trained in the language, but demonstrated pointing.
The language designed by Premack for an ape was not verbal; Premack's chimpanzee program differed from that of a separate research program in which other chimpanzees were raised in a human family in parallel with human babies, and taught words.
[2] The experiments with those chimpanzees did not demonstrate the existence of the faculties shown by Sarah discussed below, in her command of a language, for example.
In other experiments, other chimpanzees have been taught American Sign Language (ASL), notably Washoe.
However, Nim,[5] trained in ASL, was found to demonstrate no forms with grammar, his linguistic productions being sets of gestures in no particular order.
The language consisted of a series of colored plastic tokens, which the chimpanzees could manipulate and stick to a magnetic board.
The chimpanzee Elizabeth would be symbolized by a decorated E token, a copy of which would dangle from a necklace around her neck.
It took Sarah, Elizabeth, and Peony each hundreds of trials to first form an association between the tokens and the objects.
In particular, the noun had to be at the beginning and the verb had to be at the end of the production, or else the trainer would not respond to Sarah's ungrammatical sentence.
In these trials, problems were formulated by videotaped situations involving an actor, both friendly and unfriendly.
[5] However, Kanzi,[8] at age 30 months demonstrated spontaneous production of gestures and keyboard presses to ask for desired objects or events, and to name items in response to queries from the trainer.