Spontaneous Symbol Acquisition and Communicative Use by Pigmy Chimpanzees (Pan paniscus) Savage-Rumbaugh, McDonald, Sevcik, Hopkins and Rubert (1986).

Abstract Pygmy chimps are used (Pan paniscus) 2 chimps that have learnt language from other chimps. Can produce agent-verb-recipient combinations. Common chimpanzees (Pan troglodytes) are unable to do this. Use simple verbs only referring to the addressee.

What’s in a name? Associational learning – symbol enables the acquisition of a particular object. Representational learning – comes after associational learning and means that the ape can label objects and refer to objects that are not present.

Understanding Spoken English Words Disappointing results from previous research.

Language Learning without Training Research based on Pygmy chimps Kanzi mainly and younger half-sister Mulika. They are highly social animals and thus are more likely to have a predisposition for acquiring language.

Subjects Pan Paniscus – reared with access to mother. Kanzi 4 years old male, born in captivity whereas mother (Mutata) was caught in the wild. Started learning at 6 months. Also Mulika the younger half-sister who was attached to humans.

Subjects Pan Troglodytes – reared with language between 1975 to Austin and Sherman. They started language training at 1½ and 2½ years respectively.

Communication System Lexigram board – computer with voice synthesiser, but pointing board was used in the field owing to the computer board not being robust enough. 100 ASL (American Sign Language) signs were also used. The pointing boards were not so good for use by the Pan troglodytes as they use broad hand movements.

Early Rearing and Exposure to Lexigrams Matata (mother) was trained whilst she was looking after Kanzi. Kanzi was not trained at this time but could observe his mother training. Kanzi often interrupted. At 1½ years Kanzi showed an interest in the keyboard, randomly pressing keys to obtain food. Mulika (younger sister of Kanzi) did not observe her mother training but did observe Kanzi.

Rearing and exposure to Lexigrams following separation from Matata (Mother). The Pygmy chimps Kanzi and Mulika were trained in a similar way to the Common Chimpanzees Sherman and Austin, except that the common chimps could not use a portable keyboard and they did not understand human speech, so tones were used every time a symbol was pressed. Kanzi and Mulika had synthesised speech on their keyboards.

Rearing and exposure to Lexigrams following separation from Matata (Mother). Kanzi and Mulika did not have formal training because: –A) they began using symbols without training. –B) They identified symbols regardless of the position on the board. –C) They did not confuse symbols for similar items. –D) They understood spoken English.

Naturalistic Outdoor Environment Kanzi and Mulika were trained to collect food from locations around a wood. Started training with pictures of food. Kanzi could select the picture that represented the food that he wanted to travel to. Upon retrieval the chimps were given the opportunity to carry their food in a backpack if they responded positively to the question.

Naturalistic Outdoor Environment If Kanzi chose a food that was already in his backpack he was then asked whether or not he wanted to eat the food in the backpack or travel to the location where the food was stored. After 4 months of training Kanzi (aged 3 years) was able to lead a ‘blind’ experimenter to the correct locations of chosen foods.

Indoor environment Kanzi and Mulika, like Austin and Sherman join in household chores and enjoy entertainments including specially prepared videos with lexigram subtitles.

Data Recording Records for Kanzi from 2½ years old until 17 months after that. Symbol use was automatically recorded indoors, but researchers took notes when outdoors with the portable lexigram board. Mulika was studied from 11 until 21 months. Utterances were recorded as spontaneous, imitated or structured (which means replies to questions from the researchers).

Vocabulary acquisition criteria A lexigram was said to have been learnt if it occurs nine times out of 10 spontaneously and was verified (concordance between sign and behaviour). A sign could be dropped from the chimp’s vocabulary if it was not used correctly 90% of the time.

Vocabulary acquisition criteria Four and a half hours of videotape was checked by an independent observer. The original observer (real-time observer) was not aware of the checking procedure. There was 100% agreement. Nine utterances were noted by the independent video observer that were not noticed by the real-time observer. This suggests that many signs are missed in real-time.

Tests of productive and receptive capacities. Tested informally in everyday situations. At the end of 17 months Kanzi was tested under control blind lab conditions. The testing took place in the afternoon with between 20 and 14 trials in one session. Three or four alternatives were used. Alternatives were not used on consecutive trials. All of the alternatives were selected from targets.

Tests. Photograph to lexigram- shown a photograph and have to choose one of three lexigrams. The alternatives were selected by a second blind experiment and the choice was not observed by the original observer (behind a folding blind). Spoken English to photograph- “Kanzi, can you show me X?”

Tests. Spoken English to lexigram Synthesised speech to lexigram- as a control for intonation. The word was sounded twice and 4 lexigrams were presented. Sherman and Austin were tested on their vocabularies without the spoken English tests. They were rewarded with food unlike Kanzi and Mulika.

Untutored gestural usage: some observations. Between 6 and 16 months Kanzi and Mulika used iconic gestures for travel and actions. For example pointing, twisting for undoing lids, cracking nut gestures, blowing up a balloon. These were often accompanied by affective vocalisations.

Untutored gestural usage: some observations. Sherman and Austin only used gestures when being given full human attention, and would not persist. They did not elaborate or give specific gestures but just generally pointed.

First appearance of lexigram usage for communicative purposes. After a separation from the mother Kanzi’s use of the keyboard was less random and more purposeful. Could indicate particular foods, or ball to play with.

First appearance of lexigram usage for communicative purposes. Mulika began to show signs at 12 months. Tended to use “milk” for a variety of activities. After two months symbols began to be selected more appropriately. After “milk” the second symbol was “surprise” which indicated a randomly selected reward. Kanzi learnt the symbol “strawberries” whilst eating mushrooms and at first only used this symbol in this context.

Progress during the 17 months after the initial separation from Matata. Kanzi 7 words at 30 months. 44 words at 46 months (productive) (over 50 receptive) but 5 words dropped out of use. Combinations at 46 months were approximately 800. Kanzi’s receptive mode higher than productive mode. 80% were spontaneous.

Progress during the 17 months after the initial separation from Matata. Mulika “milk” at 17 months. Six words at 22 months. Kanzi’s keyboard grew as the vocabulary grew, whereas Mulika had to contend with a large keyboard from the start.

Combinations 6% of utterances. Produced combinations without repetition, such as “ice water go” meaning get some ice water, rather than “play me Nim play” (Terrace et al 1979). Kanzi produced 2,540 utterances compared to 19,000 for Nim. Kanzi used combinations for games or to benefit others, whereas Nim’s combinations were for food for himself only.

Combinations Kanzi invented combinations that asked researchers to chase each other, which was not demonstrated in advance.

The issue of imitation. Kanzi and Mulika’s utterances were truly spontaneous whereas Sherman and Austin’s were often prompted by some activity of the researcher (e.g. placing food).

Formal tests. Kanzi and Mulika understood the abstract nature of these tests. No rewards or activity would follow the choice. Sherman and Austin expected to be rewarded according to their choice.

Formal tests. Sherman and Austin were unable to do the Spoken English tests and would show signs of frustration (scratching all over their bodies). They would instead attempt to mimic spoken English unsuccessfully.

Formal tests. As a control for the possibility that Kanzi might be responding to voice intonation he was tested on a Votrax speech synthesizer. Each symbol was presented three times and was paired with two alternatives. Kanzi did well on this task.

Announcement and Verification of Travel Plans. Kanzi learned the location of 17 food sites within 4 months. During a blind test of Kanzi’s knowledge of the foraging sites, he selected a photograph, a lexicon or both. Each time he then led the experimenter to the correct location. On nearly all of the trials, Kanzi took the most direct route possible.

General observations regarding Kanzi and Mulika’s symbol usage. Kanzi mainly and to an extent Mulika generalise their symbols to other related objects. For example ‘coke’ is generalised to all dark fizzy drinks or ‘rain’ is used to refer to water from a garden sprinkler. Kanzi sometimes uses the food names to indicate where he wants to go in the woods.

Discussion It is recognised that the sample size of 2 pygmy chimps and 2 common chimps is small. Also the environments were different for the two pairs of chimps. Nonetheless it was felt that the empirical evidence was so strong as to discount these possible confounding variables. 4 discussion points follow.

Discussion 1. Kanzi and Mulika learnt rapidly whereas Austin and Sherman needed a lot of coaching. Kanzi and Mulika spontaneously recognised that lexigrams can stand for objects and events. They did not need to differentiate between naming and requesting and their receptive skills preceded their productive skills (they understood words before they used them).

Discussion 2. Kanzi and Mulika understand spoken English whereas Austin and Sherman do not, they relied more on pointing to indicate which object was to be retrieved, for example. Also Kanzi and Mulika did not require strong contextual clues.

Discussion 3. Kanzi and Mulika could be more precise with their symbols. Austin and Sherman would confuse ‘juice’ and ‘coke’ and could only handle broad definitions, whereas Kanzi and Mulika readily differentiated between lexigrams for similar items.

Discussion 4. Kanzi could ask for A to act on B, where neither A nor B was Kanzi, whereas Austin and Sherman could only form requests that involved themselves.

Conclusion Assuming that Kanzi and Mulika are representative of typical pygmy chimps it is concluded that pygmy chimps have a far greater propensity for the acquisition of symbols than other apes.

The End