This PDF includes a chapter from the following book: The Cognitive Animal Empirical and Theoretical Perspectives on Animal Cognition © 2002 Massachusetts Institute of Technology License Terms: Made available under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License https://creativecommons.org/licenses/by-nc-nd/4.0/ OA Funding Provided By: The open access edition of this book was made possible by generous funding from Arcadia—a charitable fund of Lisbet Rausing and Peter Baldwin. The title-level DOI for this work is: doi:10.7551/mitpress/1885.001.0001 Downloaded from http://direct.mit.edu/books/edited-volume/chapter-pdf/677498/9780262268028_c002400.pdf by guest on 25 September 2021 Chimpanzee Ai and Her Son Ayumu: An Episode of Education by Master- 25 Apprenticeship Tetsuro Matsuzawa I have been studying chimpanzee (Pan troglo- use has never before been found in nonhuman dytes) intelligence both in the laboratory and animals. Humans show strong hand preference in the wild (Matsuzawa 2001). Chimpanzees in on the individual level, and there is also a strong the wild use and manufacture a wide variety of right bias at the population level. The chimpan- tools, such as twigs to fish for termites or a pair zees of Bossou show a slight bias toward the of stones to crack open hard-shelled nuts. Re- right for hammering at the population level, with cent studies comparing di¤erent communities of about 67 percent of group members being right- chimpanzees have shown that each community handers. However, there is perfect correspon- develops its own unique set of cultural traditions. dence in siblings’ hand preference. Members of Chimpanzees in the laboratory can also mas- every sibling pair we have come across prefer to ter various kinds of skills, including, to some use the same hand for hammering. Hand prefer- extent, linguistic and numerical abilities. One ence is thought to be related to functional lateral question arising from these studies concerns the asymmetry of brain function, but, with many social transmission of knowledge and skills unanswered questions, this remains a controver- across generations. How and when does such sial issue in nonhuman animals. learning occur and who passes it to whom? To Young chimpanzees require at least 3.5 years address these questions, this essay briefly sum- to master nut cracking. Furthermore, there is a marizes our attempts at synthesizing two distinct critical period for learning between the ages of approaches to understanding the nature of chim- 3.5 and 5 years. Chimpanzees who fail to learn panzee intelligence: ethological observation in to crack nuts by the end of this period will not the wild and psychological experiments in the acquire the skill in later life. Learning is aided by laboratory. In addition, it also provides an ac- a form of education by master-apprenticeship. count of one of the most impressive episodes of Young chimpanzees learn the skill by carefully learning by an infant chimpanzee from a skillful observing the behavior of adults for a long time mother. after birth. This observation tends to be a one- way process. Adult chimpanzees seldom observe the behavior of the younger members of the Wild Chimpanzees at Bossou community. In addition to nut cracking, Bossou chim- The forests of Bossou, Guinea-Conakry in West panzees possess a unique repertoire of tool- Africa, are home to a group of about 20 chim- manufacturing and tool-using skills. These panzees. They are known to use a pair of stones include the use of leaves for drinking water, as hammer and anvil to crack open oil palm nuts pestle-pounding of oil palms, fishing for safari in order to gain access to the kernel inside the ants with a wand, scooping algae floating on a hard shell (figure 25.1). Through long-term ob- pond with a stick, and so forth. servation of the nut cracking, my colleagues and Chimpanzees in the wild have to learn many I have identified various interesting aspects of things besides tool use. For example, there are this tool-using behavior (Matsuzawa 1994). about 600 di¤erent species of plants in the forests For example, each chimpanzee shows perfect of Bossou; of these, the chimpanzee food reper- laterality in using hammer stones. The ‘‘right- toire includes about 200 species. Various parts of handers’’ always use the right hand for ham- the plants are eaten: the fruit, leaves, young mering, while the ‘‘left-handers’’ use their left stem, and the bark. Fruits such as figs are highly hand exclusively. Such perfect laterality in tool prized, but e‰cient foraging has several pre- Downloaded from http://direct.mit.edu/books/edited-volume/chapter-pdf/677498/9780262268028_c002400.pdf by guest on 25 September 2021 Tetsuro Matsuzawa 190 Figure 25.1 Chimpanzees at Bossou cracking oil palm nuts using a hammer stone and an anvil stone. Infant chimpanzees, which usually accompany their mothers everywhere, observe the mothers’ behavior. There is no active teaching; however, mothers are very tolerant of the infants’ observation. requisites. Chimpanzees must remember where Observational studies in the natural habitat the fig trees are located in the forest. In addi- are a fountain of information about chimpanzee tion, they have to know what time of year the intelligence, as well as their society and ecology. fruits are ripe. They must recognize that, for in- However, the constraints associated with obser- stance, the red, mature fruit is tasty, while the vation in the wild preclude us from seeing many green, unripe one is not. They have to learn how of the details of chimpanzee behavior. to reach the fruit in a large tree. Fig trees can grow to be enormous, too large for the chim- panzees to directly climb the trunks. Instead, Ai Project they have to remember routes along the branches of nearby trees to reach their destination. Chimpanzees in captivity apply the intelligence evident in the wild to surviving in the human Downloaded from http://direct.mit.edu/books/edited-volume/chapter-pdf/677498/9780262268028_c002400.pdf by guest on 25 September 2021 Chimpanzee Ai and Her Son Ayumu 191 environment. They must learn various skills to cades, she has from the age of 1 year learned to communicate with their human cohabitants. In communicate through letters and numerals using many cases in captivity, chimpanzees have a very a computer-controlled device. For example, she limited range or freedom to move from one place learned to touch letters and numerals on a com- to another, to get food, to meet conspecific puter terminal to represent the color, identity, friends and then to leave them (referred to as the and number of items shown to her (figure 25.2) fission-fusion of parties), and so forth. They are (Biro and Matsuzawa 1999; Kawai and Matsu- in a sense forced to utilize their intelligence to zawa 2000; Matsuzawa 1985). adapt themselves to the human way of commu- nication and lifestyle. Such is the general and common background to the studies of ape intel- A New Project: Infants Reared by Their Mothers ligence and ‘‘ape language’’ projects so far. Wolfgang Koehler pioneered the study of A common disadvantage of captive research chimpanzees. During the early 1910s, he main- is the lack of ‘‘community.’’ Most of the ‘‘ape- tained a group of young chimpanzees in a facility language’’ studies have concentrated on a single located on an island o¤ the west coast of the subject or a simple aggregation of multiple sub- African continent. His research methods in- jects. Chimpanzees in the wild live together in a volved providing test situations for the chim- community, which is itself often divided into panzees in which they were required to solve a small parties. Infants less than 3 years old always problem. For example, he suspended a piece of accompany their mothers. They cling to the banana high up in the air and laid out a selection mother and the mother in turn embraces the in- of sticks and boxes. Chimpanzees were found to fant. This is the natural way of life and the nat- move boxes to the spot right underneath the ba- ural context for learning in the wild. nana, to stack the boxes, to use a stick to prod Ai gave birth on April 24, 2000. In addition to the banana while standing on the boxes, and Ai, two other female chimpanzees, Chloe´ and even to join two sticks together to extend their Pan, also gave birth soon thereafter. Together instrument if the fruit was still out of reach. In with these babies, we now have a group of 14 sum, Koehler demonstrated that chimpanzees chimpanzees at the Primate Research Institute in have the intelligence to make and to use tools for Inuyama. The members’ ages range from the solving given tasks. Today, we can see many newborns to a 36-year-old, encompassing three parallels between the observations in Koehler’s generations of both sexes. This is the Inuyama classic work in captivity and the tool manu- community of chimpanzees, which simulates the facturing and use seen in the wild. natural way of life of chimpanzees in the African Besides tool use, apes raised in a human envi- forest (figure 25.3). ronment can, to some extent, learn how to use In our outdoor compound, we have planted human signs. Through such long-term rearing more than 500 trees from 60 di¤erent species and and training projects, the Gardners and Pre- built climbing frames more than 50 feet high. macks, as well as other researchers, have con- The chimpanzees are free to stay outside all tributed a great deal to our understanding of the day for as long as they wish.