Savage-Rumbaugh (1986)


What is the difference between language and communication? Language is a small number of signals (sounds, letters, gestures) that by themselves are meaningless, but can be put together according to certain rules to make an infinite number of messages. Communication, on the other hand, is the way in which one animal or person transmits information to another and influences them.

There is no common agreement on what constitutes language. However, numerous features have been identified as common to all humans. The 4 main features which show the difference between human language and animal communication are:

  • Displacement: the ability to speak about the present, past and future. It is widely believed that humans are the only ones capable of this.
  • Productivity: the ability to invent new signals in order to describe new ideas.
  • Arbitrariness (chance): there is no natural connection between a word or sound and the thing it denotes, we can not tell the meaning of the word simply by looking at it or hearing it.
  • Cultural transmission: the language used around us, by our family, determines the language we speak.

Previous research have demonstrated the ability of chimpanzees to acquire language. For example, The Kelloggs found that their chimpanzee Gua, who was brought up with their son Donald, could follow simple commands e.g. show me your nose. However he did not learn language. Similarly, the Gardeners were able to teach Washoe, a common chimpanzee, 250 signs of American Sign Language, which he used consistently. However, there is still a debate as to whether this was language or simply imitation.

There are many theories of language. The behaviourist theory, developed by Skinner, proposes that children learn language by imitation and reinforcement. Through the process of operant conditioning, a child imitates what he/she hears and is positively reinforced when correct. As a result, vocalisations are gradually shaped and words are learned. This theory supports the nurture side of the nature-nurture debate.
Although this theory is considered as significant by many researchers, it has been criticized for not explaining the learning of language rules, as carers will often reward a child when the meaning of their utterance is clear even though the syntax may be incorrect. The Nativist theory, developed by Chomsky, proposes that children are born with an innate Language Acquisition Device (LAD). The ability to learn & use language is hard wired into the human brain and thus humans are biologically programmed to learn language. This theory supports the nature side of the nature-nurture debate, arguing that grammar and rules of language are too difficult to be learnt through reinforcement – not all rules are reinforced!
In order to determine which theory is correct, research has been done into whether apes can learn language.


To study the language acquisition of two pygmy chimpanzees, Kanzi and Mulika, compared to two ‘common’ chimpanzees, Austin and Sherman.

Method & Design

The method used was a case study with a longitudinal design.

The data reported on was gathered over a 17 month period – from the time Kanzi was 30 months until 47 months old

Can also be considered a quasi-experiment because comparisons were made between the Pygmy and Common chimpanzees.


At the time the report was written:

  • Kanzi – 4 year old pygmy chimp, born 28/10/80
  • Mulika– 3 year old pygmy chimp, sister of Kanzi,

Both Pygmy chimps were born in captivity in the Yerkes Regional Primate Centre, USA. Both were reared in a language-using environment, with access to their mother, Matata.

  • Austin – 9 year old common chimp.
  • Sherman -10 year old common chimp.

Both reared in a language using environment.

When Kanzi was 2 ½ years old, after he has been separated from his mother, he spontaneously started to use symbols (he has observed his mother using the Lexigram Keyboard).

Without training Kanzi identified symbols correctly and did not confuse them (e.g. apple, orange, banana) he also understood spoken words.

Kanzi and Mulika had been chosen because the pygmy species have better social skills than other chimps. Also, Kanzi had seen his mum use the lexigram with trainers and started to show an interest in using it too. The 2 common chimps (Austin and Sherman) used for comparison.


Because chimpanzees do not have the appropriate vocal chords to reproduce using human speech, they used different methods to communicate.

Indoors: Kanzi used a battery powered keyboard with geometri symbols (lexigrams) which when pressed lit up. A speech synthesiser then said the word.

Outdoors: Kanzi used a laminated copy of the keyboard as a ‘pointing board’

Spoken English accompanied the experimenters’ lexigram communications, and gestures were also used with all four chimps. Most gestures were informal, spontaneous and natural accompaniments to speech. The experimenters also used approximately 100 American Sign Language gestures.

Rearing Environment: Kanzi was separated from his mother so she could take part in a breeding program. When she returned 4 months later, Kanzi had developed a preference for human company. At 4 months of age, Mulika developed an eye infection and was taken away for treatment where she too developed a preference for human company. Mulika did not therefore see her mother using lexigrams, but did observe Kanzi using them.

Kanzi and Mulika’s rearing environment after separation from Matata was similar to that of Austin and Sherman, but there were also differences:-


  • Attachment to caretakers
  • Opportunity to interact with and observe people
  • Exposure to human speech
  • Exposure to gestures, photographs, novel objects, types of formal tests, and discipline
  • Opportunity to watch television.


  • Sherman and Austin were in a training setting, whereas Kanzi and Mulika were in an observational setting.
  • Sherman and Austin’s keyboard did not have a speech synthesizer because tests revealed that they did not understand spoken English.
  • Sherman and Austin did not use a keyboard outside the laboratory.

Kanzi’s outdoor environment was 55 acres of forest in which specific food types are stored at 17 different locations. He must therefore travel to get the food type he wants. Kanzi learned where all the food was located and could select a food from photos on the ground and could guide another person to his chosen location. He learned to use the symbols on the keyboard to indicate where he wanted to go

Data collection

  • From Kanzi’s first use of the lexigram at the age of 2 ½ a complete record was kept of all his utterances for 17 months.
  • The same was kept for Mulika from 11-21 months.
  • Indoor data: computerised records from keyboard
  • Outdoor data: notes from observers when outside

Each utterance was classified:


Also concordance was looked at: the use of the word backed up by behavioural conformation e.g. if request to ‘go to treehouse’ led a person to the treehouse


2530 correct combinations of symbols, many being ‘two foods’ e.g. hotdog and coke, were recorded. 265 instances of imitating symbols were recorded.

Between 6 and 16 months of age both Kanzi and Mulika spontaneously began to use gestures to communicate preferred directions of travel and actions they wished to have performed.

Similar gestures were observed in Austin and Sherman when they were older (between 2 and 4 years).


There were 4 main differences between the Pygmy chimpanzees and the Common chimpanzees:

  • Kanzi and Mulika comprehended the lexigrams with far more ease, and used them far more spontaneously without the need for training
  • Kanzi and Mulika were far more able to comprehend spoken English words.
  • Kanzi and Mulika used lexigrams far more specifically e.g. to differentiate between coke and juice, than Austin and Sherman who used broader categories e.g. food.
  • Kanzi was able to refer to requests involving others. Austin and Sherman never formed requests in which someone other than themselves was the beneficiary.


The results suggest that pygmy chimpanzee’s exhibit symbolic and auditory perceptual skills that are distinctly different form those of common chimpanzees.

The researchers were surprised that two closely related species differed so greatly in their capacity to acquire a functional symbolic communication system, specifically in their ability to comprehend spoken speech.

They suggest that this finding minimises the significance of the behavioral differences between humans and apes and point out the findings highlight the power of cultural learning.

Controls in the study: 

  • One block of 4 ½ hours of observations made in real time was compared with another set of observations made from a videotape of the same 4 ½ hours by 2 observers
  • Observer did not know the record would be used for reliability check
  • There was 100% agreement with regard to the lexigrams used and their correctness but one disagreement about whether it was spontaneous or not.



+ The case study method and longitudinal design provides rich insightful data into language acquisition. It also enables the researcher to develop a close relationship with participants which allows more natural behaviour to be observed.

+ High ecological validity as Kanzi was able to roam around 55 acres of woodland. This generalises to his natural environment, therefore findings are representative of day-to-day situations.

+ Both quantitative and qualitative data was gathered under rigorous control and are therefore less likely to be open to bias and subjectivity. This increases the validity and reliability of the research.


– The case study method leads researchers to become emotionally involved with their participants – therefore the way behaviour was interpreted in this study may have lacked objectivity due to observer bias, thus making the findings less valid.

– The sample was very small and specific and therefore not representative of normal pygmy chimpanzees. Kanzi and Mulika were reared from birth in a ‘language environment’, and therefore the findings cannot generalise to chimps not raised in this setting.

– Animal research raises many ethical issues, for example, because these chimpanzees were reared away from their natural environment for the purpose of human research, they may have became ‘humanised’ and were therefore unable to return to their natural habitat thus developing human dependency.

Click here for model answers and exam practice

Useful resources:

Section A Questions

Section B Questions

Multiple Choice Quiz

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