Aims
Having spent her career working with apes, Sue Savage-Rumbaugh hopes to settle the language debate and show that pygmy chimpanzees have human language capabilities.
In order to demonstrate this, the apes need to show language-use spontaneously (without being trained) and should demonstrate STRUCTURE DEPENDENCE or syntax - putting symbols into a special order to convey different meanings.
The sample
This is a case study and the main subject was a bonobo ape (pygmy chimpanzee) named Kanzi. Bonobos are smaller than common chipanzees, more sociable (they share food) and seem to be brighter. The researchers compared Kanzi (age 3) and his sister Mulika (age 1) with a pair of common chipanzees named Austin and Sherman. These two chimps had been trained to use symbols the regular way, with rewards.
Kanzi used to go with his mother to her language classes. He was never "taught" any symbols but he started to use them spontaneously when his mother went away on a breeding programme. Presumably he saw his mother using symbols and copied her, because when Kanzi's sister was born she started using symbols that she had learned from her big brother!
Procedure
Apes cannot talk (they don't have vocal chords) but they have a lot of skill with gestures. Savage-Rumbaugh designed a board containing dozens of LEXIGRAMS. These were brightly coloured squares that represented pastimes ("chase"), food ("strawberry"), people and places - there's a picture on the right. The apes learned to point to certain lexigrams to communicate their wishes. Humans would act as role models around the apes when talking to each other by pointing to the lexigrams for the words they were using.
There were two versions of the lexigram board. Indoors there was an electronic board connected to a computer. When a lexigram was pressed it lit up, the computer recorded it and an electronic voice would speak the word out loud. Outdoors there was a tough laminated board and observers would record which lexigrams the apes pointed to and enter the data into the computer later. Every utterance was classed as correct or incorrect, but also as spontaneous, imitated or structured: imitated utterances repeated back symbols a human had used while structured utterances used symbols in reply to a request or a question.
The apes lived in a 55 acre wooded park with 17 named locations where different types of food were placed. To get food, the apes had to go to these locations. At first Kanzi was shown photographs of different food and taken to the location of the food he chose. Within 4 months Kanzi could select a photo and guide others to the right place (often carrying Mulika!). Later, he and Mulika could use the lexigrams to choose their own meals and journeys.
Tests and measures
Before a symbol counted as part of Kanzi's language, it had to be verified on 9 out of 10 occasions. If Kanzi indicated he wanted to go to the treehouse then took the experimenter to the treehouse, this counted as POSITIVE CONCORDANCE - proof that Kanzi was acquiring the symbol for "treehouse".
The reliability of the observations had to be tested, so 4½ hours of observations were videoed and another observer watched the tape. There was 100% agreement on the correctness of the lexigrams and one disagreement about spontaneity.
Sometimes the lexigrams were moved to new positions, but the apes had no problem identifying them. At the end of the 17 month study, Kanzi was tested on his knowledge of lexigrams. Kanzi was either shown a photograph or listened to a word, then had to identify the right lexigram.
Outcomes
When young, Kanzi started using the "chase" lexigram to get humans to play with him and spontaneously invented a gesture (hand clapping) with the same meaning. Kanzi and Mulika both invented gestures (eg to tell humans to blow up balloons for them) and these gestures were clearer and more explicit than those used by the chimpanzees Sherman and Austin.
Kanzi started using lexigrams when his mother went away (when he was 2½) and Mulika began using lexigrams properly at 14 months. The apes used symbols through association first. For example, since Kanzi was introduced to strawberries at the mushroom site, for a while he used the "mushroom" lexigram for strawberries. Human children use similar associations when learning words. The apes were like children also becuse they imitated more often when learning new words - about 15% of their utterances were imitated and 80% were spontaneous and this is about the same for human children. By the end of the study, Kanzi had acquired 46 words and Mulika 37.
Kanzi went on to combine symbols together. Over the 17 months, Kanzi produced 2540 non-imitated combinations, along with 265 that were prompted or partly imitated: all but 10 were judged by observers to be appropriate and comprehensible. In the formal tests the bonobo apes did well and had no problem understanding spoken words, even from the voice synthesizer machine (which the researchers had difficulty understanding!). The chimpanzees Austin and Sherman did less well, because when they identified an object (eg "banana") they expected to be given it as a reward.
Sometimes Kanzi took the lexigram board off by himself, as if he wanted to practise with it. Kanzi was also introduced a a visitor who had never been to the woods before (and therefore couldn't provide any cues). Kanzi was able to identify a photo or lexigram and guide the "blind" visitor to the right place. Kanzi could also guide the visitor to locations identified by spoken English rather than symbols.
Conclusions
Although Kanzi produced fewer combinations than other language chimps in previous studies, his three-symbol phrases never referred to himself, whereas the famous Nim Chimpsky who produced 19,000 combinations would often say things like "more eat Nim". Most chimps use language about food, whereas Kanzi mostly referred to games (eg "chase bit person").
Pygmy chimpanzees like Kanzi and Mulika seem to have a natural talent for using symbols - they were better at it than the common chimpanzees, learning the lexigrams faster and without needing training, understanding spoken English without being trained and using the lexigrams to refer to specific things (eg "juice" or "coke") whereas Sherman and Austin would use symbols interchangeably ("eg "juice" or "coke" for any drink).
Most importantly, Kanzi could use language to direct other people to do things (eg request a human to chase another chimp). Sue Savage-Rumbaugh regards this as the beginnings of syntax, because word order makes it clear who is intended to do what to who. An example of this is when Kanzi was playing with his toys (a plastic dog and snake) Sue Savage-Rumbaugh used the lexigrams to make the computer say, "Make the dog bite the snake". Kanzi put the snake into the dog's mouth and pressed its jaws together. If Kanzi hadn't understood word order, he might have made the snake bite the dog instead.
