Pretend Play in Pan: How does symbolic knowledge affect representational play?

Patricia Greenfield1, Heidi Lyn2, and E. Sue Savage-Rumbaugh3
1UCLA, 2Wildlife Conservation Society, 3Language Research Center

greenfield@psych.ucla.edu

Human language is part of a suite of representational capacities
(Piaget, 1951).  The evolutionary history of these capacities is
therefore of great interest to an understanding of the phylogeny of
human language and the human symbolic capacity more generally.  One
approach is to investigate representational capacities in our closest
living relatives, the genus Pan.  Commonalities between Homo sapiens and
Pan in representational capacities indicate a possible evolutionary
foundation present 5-7 million years ago (Byrne, 1995; Cantalupo &
Hopkins, 2001; Gannon, Holloway, Broadfield, & Braun, 1998).  One
capacity of particular interest is pretend play (play behavior that has
an imaginary component) because pretend play develops so early in human
children, around the same time as early language, and proceeds through a
sequence of regular stages or steps in its development (Mitchell, 2002;
Piaget, 1951).  These stages allow us to ask not only whether apes can
imagine, but what stages are evident in their play and whether the
ordering of stages - the ontogenetic sequence - follow that of humans. 

Because most examples of pretend play in apes come from home-reared apes
or apes socialized with humans (Byrne, 1995; Mitchell, 2002; Suddendorf
& Whiten, 2001; Tomasello & Call, 1997), the influence of human
enculturation on the development of pretend play is of particular
interest.  One possibility is that the enculturation by humans
stimulates the biological capability for pretend play extant in apes. 
In that case, the human enculturation could be perceived of as
scaffolding in the Vygotskian sense - stimulating the apes' abilities
within their zone of proximal development (Vygotsky, 1978).  Pretend
play in humans has been shown to be the outcome of a scaffolding process
(Bondioli, 2001; Farver, 1993; Zukow, 1986)

Here we present the results of a systematic, qualitative study on
pretend play in the symbol-competent apes of the Language Research
Center.  These apes have been previously shown to understand English at
the level of a 2 1/2 year-old child and utilize symbols printed on a
plastic keyboard to communicate with researchers (Brakke &
Savage-Rumbaugh, 1995, 1996; Savage-Rumbaugh, McDonald, Sevcik, Hopkins,
& Rupert, 1986; Savage-Rumbaugh et al., 1993) Our data come from over
100 hours of videotape taken over the course of 10 years of study on
three bonobos (Pan paniscus) and two chimpanzees (Pan troglodytes). 

We utilize the levels of pretend play described by McCune and Agayoff
(2002) and based on descriptions by Piaget (1951).  Our results show
that the language-competent apes demonstrate pretend play up to level 4
spontaneously, but all examples of level 5 (the highest level) pretend
play are initiated or scaffolded by human researchers.  In contrast, the
non-language-competent apes show pretend play at much lower stages than
the language-competent apes and are unaffected by the researchers
scaffolding attempts.  These results suggest that sharing in human
symbolic culture plays an important role in apes reaching higher stages
of pretend play.  The symbol-competent apes, therefore, provide us with
an important model to further study the relationship between language
and pretend play. 


Bondioli, A.  (2001).  The adult as a tutor in fostering children's
symbolic play.  In A.  Geoncue & E.  L.  Klein (Eds.), Children in play,
story, and school (pp.  107-131).  New York, NY: Guilford Press. 

Brakke, K.  E., & Savage-Rumbaugh, E.  S.  (1995).  The development of
language skills in bonobo and chimpanzee - 1.  Comprehension.  Language
and Communication, 15(2), 121-148. 

Brakke, K.  E., & Savage-Rumbaugh, E.  S.  (1996).  The development of
language skills in Pan - II.  Production.  Language & Communication,
16(4), 361-380. 

Byrne, R.  W.  (1995).  The thinking ape : evolutionary origins of
intelligence.  Oxford ; New York: Oxford University Press. 

Cantalupo, C., & Hopkins, W.  D.  (2001).  Asymmetric Broca's area in
great apes: A region of the ape brain is uncannily similar to one linked
with speech in humans.  Nature, 414(6863), 505. 

Farver, J.  A.  M.  (1993).  Cultural differences in scaffolding pretend
play: a comparison of American and Mexican mother-child and
sibling-child pairs.  In K.  MacDonald (Ed.), Parent-child play:
descriptions and inplications (pp.  349-366).  Albany, NY: State
University of New York Press. 

Gannon, P.  J., Holloway, R.  L., Broadfield, D.  C., & Braun, A.  R. 
(1998).  Asymmetry of chimpanzee planum temporale: Humanlike pattern of
Wernicke's brain language area homolog.  Science, 279, 220-222. 

McCune, L., & Agayoff, J.  (2002).  Pretending as representation: a
developmental and comparative review.  In R.  W.  Mitchell (Ed.),
Pretending and imagination in animals and children (pp.  43-55). 
Cambridge: Cambridge University Press. 

Mitchell, R.  W.  (2002).  Pretending and imagination in animals and
children.  Cambridge: Cambridge University Press. 

Piaget, J.  (1951).  Play, dreams and imitation in childhood.  New York,
NY: Norton. 

Savage-Rumbaugh, E.  S., McDonald, K., Sevcik, R.  A., Hopkins, W.  D.,
& Rupert, E.  (1986).  Spontaneous symbol acquisition and communicative
use by pygmy chimpanzees (Pan paniscus).  Journal of Experimental
Psychology: General, 115(3), 211-235. 

Savage-Rumbaugh, E.  S., Murphy, J., Sevcik, R.  A., Brakke, K.  E.,
Williams, S.  L., & Rumbaugh, D.  M.  (1993).  Language comprehension in
ape and child.  Monographs of the Society for Research in Child
Development, 58(3-4), v-221. 

Suddendorf, T., & Whiten, A.  (2001).  Mental evolution and development:
evidence for secondary representation in children, great apes, and other
animals.  Psychological Bulletin, 127(5), 629-650. 

Tomasello, M., & Call, J.  (1997).  Primate Cognition.  New York: Oxford
University Press. 

Vygotsky, L.  S.  (1978).  Play and its role in the mental development
of the child.  In M.  Cole, V.  John-Steiner, S.  Scribner & E. 
Souberman (Eds.), Mind in Society.  Cambridge, MA: Harvard University
Press. 

Zukow, P.  G.  (1986).  The relationship between interaction with the
caregiver and the emergence of play activities during the one-word
period.  British Journal of Developmental Psychology, 4, 223-234.