Journal of Comparative Psychology 1992, Vol. 106, No. 4, 398-403
Copyright 1992 by the American Psychological Association, Inc. 0735-7036/92/S3.00
Object Manipulation and the Use of Tools by Infant Baboons (Papio cynocephalus anubis]
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Gregory Charles Westergaard University of Washington Infant baboons (Papio cynocephalus anubis) in a captive peer group used objects as containers, drinking utensils, and sponges in the context of play. The baboons later used paper, browse, and other materials as tools to extract sweet liquids from apparatus designed to accommodate sponging and probing behavior. The results of this study demonstrate flexible combinatorial manipulation and spontaneous use of tools by infant baboons. These data are consistent with hypotheses that (a) an evolutionary history of omnivorous extractive foraging is associated with the use of tools and (b) free play in an object-enriched captive environment may facilitate combinatorial manipulation in nonhuman primates.
Object manipulation and the use of tools by nonhuman primates have held scientific interest for many years (for a review, see Chevalier-Skolnikoff, 1989). The propensity for sophisticated manipulative behavior in great apes and capuchin monkeys has led to considerable speculation about the evolutionary origins of underlying sensorimotor strategies. Parker and Gibson (1977) and Chevalier-Skolnikoff (1989) have proposed a hypothesis of phylogenetic discontinuity in the expression of combinatorial manipulation. They have argued that flexible combinatorial manipulation evolved separately in the ancestors of great apes and capuchin monkeys but not in the ancestors of other nonhuman primates, as a result of selection pressures that favored omnivorous extractive foraging. Research with lion-tailed macaques (Macaca silenus) has indicated that combinatorial manipulation may be more prevalent among nonhuman primates than was proposed by Parker and Gibson (1977) or Chevalier-Skolnikoff (1989). In an empirical study lion-tailed macaques in captive social groups spontaneously manufactured and used tools to extract sweet syrup from an apparatus designed to accommodate probing behavior. The macaques prepared tools by detaching sticks from larger branches and sometimes modified their tools further by subtracting projecting stubs, leaves, and bark (Westergaard, 1988). Lion-tailed macaques are now known to use tools in nature (Bhat, 1990), where they consume a broad variety of foods and sometimes extract their prey (Johnson, 1985). These reports have provided further evidence for continuity among primates in the expression of combinatorial manipulation and are consistent with the hypothesis that an evolutionary history of omnivorous extractive foraging is
associated with the use of tools (Westergaard, 1988; Westergaard & Fragaszy, 1987). The finding that lion-tailed macaques manufacture and use tools has led me to speculate that other omnivorous Old World monkeys have the potential to express similar manipulative sophistication. Baboons in nature extract and consume a broad variety of foods (Hamilton, Buskirk, & Buskirk, 1978; Whiten, 1988) and use tools in contexts that include agonistic encounters, hammering, leverage, raking, and self-grooming (summarized in Beck, 1980). However, Beck (1980) cited only two anecdotal descriptions of baboons' use of sticks as feeding implements and no reports of baboons' use of sponging material to absorb and consume water. The observation that wild baboons do not readily use sponging or probing tools is of particular interest in view of their close association with tool-using chimpanzees (Teleki, 1974). Chevalier-Skolnikoff(1989) noted that although baboons use tools in several contexts, the use of tools by individual animals remains stereotyped over time and is not consistent with the flexible combinatorial manipulation that has been noted for great apes and capuchin monkeys. To the best of my knowledge, the youngest monkeys that have used tools were capuchins (Cebus apella) aged 10-14 months (Westergaard & Fragaszy, 1987). Immature capuchins developed the use of tools over a period of several weeks as a result of trial-and-error experimentation (also see Parker & Poti, 1990). A similar acquisition pattern was noted for immature lion-tailed macaques, although these animals did not use tools until the age of 24 months (Westergaard, 1988). A recent study has indicated that baboons may also be able to use tools at a very early age (Westergaard, 1989). Infant baboons aged 7-11 months spontaneously learned to acquire food by maneuvering a plastic rod into a distant food container. Although that report described a specific and somewhat narrow instance of manipulative sophistication, it does suggest that baboons are manipulatively precocious and indicates the need for further research with additional subjects in varied and generalized tasks. The purpose of this research was to examine object manipulation and the use of tools by captive infant baboons (Papio cynocephalus anubis). Previous research has indicated that infant baboons engage in frequent and diverse manipulative
This research was conducted at the University of Washington's Infant Primate Research Laboratory and was supported by National Institutes of Health Grants HDO2274 and RR00166. I thank C. Menuhin-Hauser, M. Amorette, M. Sputnik, D. Fragaszy, and G. Sackett for support and encouragement throughout all phases of this research. Correspondence concerning this article should be addressed to Gregory Charles Westergaard, who is now at the Laboratory of Comparative Ethology, National Institutes of Health Animal Center, Building 112, Elmer School Road, Poolesville, Maryland 20837.
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OBJECT MANIPULATION IN INFANT BABOONS
actions (Joubert & Vauclair, 1986) and use objects as rakes to secure otherwise inaccessible food (Westergaard, 1989). In this investigation three experiments were conducted in the home cage of a socially housed peer group. In Experiment 1, three sets of stimulus objects were provided to facilitate the discovery of novel object relations in the context of play with no extrinsic reward. In Experiments 2 and 3, apparatus designed to accommodate sponging and probing behavior were provided along with material from which the baboons could fashion appropriate tools. The rationale was to examine the use of tools in contexts that were functionally analogous to those that have been described for chimpanzees, capuchin monkeys, and lion-tailed macaques (see Chevalier-Skolnikoff, 1989; Goodall, 1964; McGrew, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1985, 1987). On the basis of the hypothesis that an evolutionary history of omnivorous extractive foraging correlates positively with the expression of toolusing propensities, it was predicted that the baboons would engage in sophisticated manipulative actions similar to those that have been reported for other nonhuman primates that have shown a strong tendency to use tools.
Experiment 1 Method Design. Experiment 1 was designed to examine combinatorial manipulation by infant baboons in the context of play. Three sets of stimulus objects were introduced into the home cage of a socially housed peer group. In Condition 1, objects were selected to facilitate the use of containers and drinking utensils. In Condition 2, objects were selected to facilitate the use of sponges. In Condition 3, the objects used in Conditions 1 and 2 were provided to facilitate simultaneous use of containers and sponges. Subjects and apparatus. Subjects were 3 infant baboons (Papio cynocephalus papio) that ranged in age from 25-33 weeks. They included 2 males (Ivan and Jack; both 25 weeks of age at the onset of this experiment) and 1 female (Heidi; 33 weeks of age). The baboons were medically healthy members of the University of Washington Infant Primate Research Laboratory "Infant Save" program, which provides nursery rearing of infants that would not survive if left in their natal social group. These include prematurely delivered infants, infants rejected by their mothers, and infants who are injured during aggressive interactions. The baboons in this study were reared by human caretakers under standard laboratory conditions, which include daily periods of socialization to prevent isolation rearing effects (see Research Protocols Guide, Infant Primate Research Laboratory, 1986; Sackett, 1972). At the time of this experiment, the baboons were housed together in an indoor cage (1.5 m wide x 1.3 m high x 2.1 m deep). Food and water were available ad libitum. Stimulus objects were rubber balls (5 cm in diameter), plastic cups (13 cm high, 10 cm in diameter at the opening, and 8 cm in diameter at the base), paper towels (24 x 28 cm), and a plastic tub (29 x 38 x 14 cm). Procedure. One-hr observation sessions were conducted daily over a period of 3'/2 weeks. Nine sessions were conducted in Conditions 1 and 3, and six sessions were conducted in Condition 2. At the onset of each session, stimulus objects were distributed on the floor of the animals' home cage. Three balls and three cups were used in Condition 1. In Condition 2, a tub partially filled with water (to a depth of about 10 cm) and 10 paper towels were used. A plastic pipe
(30 cm in length) was skewered through the paper towels and hung in the cage about 1 m from the tub. In Condition 3, the objects used in Conditions 1 and 2 were distributed simultaneously in the manner just described. Throughout the experiment, data were collected by an observer who noted the absolute frequency of combinatorial manipulation in which one object was placed in direct relation to another, such as when an animal placed an object into a container or used a towel as a sponge to absorb and consume water. Qualitative notes and videotape provided supporting details. Analysis. Combinatorial manipulations were organized into four mutually exclusive and exhaustive categories: (a) container, an action of an animal's placing one solid object inside another; (b) drinking utensil, a two-step sequence of an animal's holding a plastic cup under the water spigot and then drinking directly from the partially filled object; (c) sponge, a two-step sequence of an animal's placing a paper towel into the plastic tub and then removing and chewing the water-laden object; and (d) other, such as an animal's placing an object in direct contact with the water spigot (causing water to freely flow) or using a plastic cup as a scoop to displace water from the plastic tub.
Results The baboons used objects as containers in 157 instances (see Table 1). Heidi and Ivan first used containers during Condition 1 (in Sessions 3 and 7, respectively), and Jack first used a container during Condition 3 (Session 3). The baboons placed several types of objects into plastic cups, including rubber balls, paper towels, and food biscuits. The baboons used cups to concurrently contain as many as two objects and repeated the action of inserting and removing an object as many as three times in one uninterrupted behavioral sequence. The baboons used paper towels as sponges to absorb and consume water in 64 instances. Heidi and Ivan first used a sponge in Condition 2 (Session 1). Jack did not use sponges during this experiment but did obtain water by drinking directly from the tub, by picking up discarded sponges from the cage floor, and by stealing sponges from the other animals. The baboons repeated the sponging action as many as four times in one interrupted behavioral sequence. Heidi was the only baboon that used a plastic cup as a drinking utensil. She first exhibited this behavior during Condition 1. Twelve min after the onset of Session 1, Heidi picked up a plastic cup from the cage floor, jumped to a perch, held the cup under the water spigot, brought the open end of the
Table 1 Experiment 1: Absolute Frequency of Combinatorial Manipulations Across Conditions Combinatorial manipulation Subject Container Sponge Heidi 68 29 Ivan 42 35 Jack 47 0 Total
157
64
Drinking utensil Other Total Rate/hr
8 0 0
18 14 0
123 91 47
32
261
5.1 3.8 2.0
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GREGORY CHARLES WESTERGAARD
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cup to her mouth, and drank directly from it. Heidi repeated this action as many as two times in one uninterrupted behavioral sequence. The baboons expressed other combinatorial manipulations in 32 instances. The animals placed objects in direct contact with the water spigot in 18 instances. Seventeen instances of this behavior were observed in Heidi, and one instance of this behavior was observed in Ivan. The animals used cups as scoops to displace water from the tub in 14 instances. One instance of this behavior was observed in Heidi, and 13 instances of this behavior were observed in Ivan.
Experiment 2 Method Design. This two-phase experiment was designed to examine spontaneous use of sponges in the acquisition and consumption of sweet juice. In Phase 1, an open container partially filled with apple juice was provided in the baboons' home cage along with paper towels that could be used as sponges to absorb and consume the liquid. In Phase 2, three containers were used to facilitate greater access to the food source among socially subordinate subjects. These tasks were designed to examine behavior functionally analogous to the use of sponging materials by chimpanzees and capuchin monkeys (see McGrew, 1977; Westergaard & Fragaszy, 1987). Subjects and apparatus. The subjects were 5 infant baboons. They included the 2 males used in Experiment 1 (Ivan and Jack; both 29 weeks of age at the onset of Experiment 2), an additional male (Karl; 24 weeks of age), and two females (Jenny and Kim; 26 and 24 weeks of age, respectively). Karl, Jenny, and Kim were reared and cared for under the conditions described in Experiment 1. The apparatus included plastic containers (12 x 12 x 17 cm with a 10 cm opening on top) and paper towels (24 x 28 cm). Procedure. Phase 1 was conducted during 12 daily 1-hr sessions. At the onset of each session, a container was partially filled with apple juice (to a depth of about 6 cm) and secured to the mesh inside the home cage. A plastic pipe was skewered through 10 paper towels and hung in the cage about 1 m from the tub. Data were collected by an observer who noted each instance in which an animal inserted a towel into the container, removed the towel, and consumed juice. Phase 2 was conducted during 9 daily 1-hr sessions. The procedure was similar to that used in Phase 1 except that three containers partially filled with apple juice were secured side-by-side to the cage mesh. During Phase 2, data were collected only for those animals that did not use sponges in Phase 1.
Results All the baboons quickly learned to obtain juice by reaching into the container with their bare hands. Three baboons used paper towels as sponges to absorb and consume juice during Phase 1. Ivan and Jack first used sponges in Session 1, and Karl first used a sponge in Session 9. The other two baboons (Jenny and Kim) first used sponges during Phase 2 (in Sessions 2 and 5, respectively), when additional containers of juice were available. Table 2 provides a quantitative summary of sponging activities. The baboons used paper towels as sponges in a total of 344 bouts (dips per bout, M = 3.3). Typically, a baboon picked up a paper towel and placed it into the juice container,
Table 2 Experiment 2: Summary of Sponging Activities Subject Ivan Jack Jenny Karl Kim
No. bouts
Mean dips/bout
88 156 61 27 12
2.0 4.8 6.2 4.9 1.7
Total
344
3.3
Note. Date reported for Ivan, Jack, and Karl were collected when one apple juice container was in the home cage. Data reported for Jenny and Kim were collected when three apple juice containers were in the home cage.
allowed the towel to soak (sometimes for 30 s or longer), removed the soaked object, and placed it directly into its mouth. The baboons consumed the juice by repeatedly chewing the soaked paper towels. The baboons acquired the use of sponges through patterns of active experimentation. The acquisition patterns exhibited by Ivan and Karl provide illustrative examples. Before his initial sponging dip, Ivan repeatedly reached into the container with his bare hand, and in one instance (3 min, 4 s into Session 1), he picked up a towel and rubbed it along the outside rim of the container's opening. Ivan quickly discarded the towel and did not obtain juice from this action. A few minutes later (8 min, 46 s), Ivan approached the apparatus and chewed the container's rim. He then turned his back to the container, picked up a paper towel, turned back to the apparatus, and rubbed the towel along the inside rim of the container's opening and downward into the juice. He then removed the wet towel from the apparatus and chewed it. At 15 min, 36 s, Ivan rubbed another paper towel against the rim of the apparatus, but he did not obtain juice from this action. Ivan completed his second sponging dip several minutes later (at 22 min, 9 s). Karl, on the other hand, acquired the use of sponges in a pattern that developed over several test sessions. During the first two sessions, Karl infrequently visited the apparatus. Karl visited the apparatus with increased frequency in Sessions 3-8, and in 11 instances he removed discarded sponges from inside the juice container. Karl chewed these soaked objects, but he did not reinsert them into the apparatus. During Session 8, Karl approached the apparatus and rubbed paper towels along the rim of the container's opening in three separate instances. Karl did not obtain juice as a result of these actions. Karl completed his initial sponging dip at 14 min into Session 9. At 13 min, 50 s, Karl picked up a towel and approached the apparatus. He then wiped the towel downward along the inside of the container and into the juice. He then removed the wet towel and chewed it. Karl picked up another towel and completed his second and third sponging dips about 1 min later. The baboons engaged in several sponging behaviors that have been noted previously for chimpanzees and capuchin monkeys (McGrew, 1977; Westergaard & Fragaszy, 1987). The baboons manufactured sponges by detaching towels from the plastic pipe, by reshaping towels with their hands and teeth, by subtracting excess portions of towel, and by combin-
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OBJECT MANIPULATION IN INFANT BABOONS
ing two or more towels in an apparent attempt to construct a more absorbent sponge. On occasion several animals used individual tools in succession, and the animals frequently stole portions of towel from unwilling conspecifics. The baboons displayed response generalization toward alternate sponging materials during informal follow-up sessions when they readily used banana chips, corn husks, cloth, and paper confetti to absorb and consume juice. The baboons gained two advantages by using paper towels rather than bare hands to absorb and consume juice. First, the use of paper towels enabled the baboons to transport juice away from the frantic activity that surrounded the apparatus. This strategy was especially useful to socially subordinate baboons because it enabled these animals to consume juice somewhat free from the harassment of conspecifics. Second, the use of paper towels enabled the baboons to absorb more juice per dip than was possible through the use of a bare hand. I conducted an informal test of the effectiveness of these two modes of absorption in order to evaluate this hypothesis. First, I inserted my hand into a container of water 10 times and then measured the volume of liquid that had been displaced. I then repeated this procedure holding an appropriately shaped paper towel. On the basis of this test, I determined that a hand with a paper towel was about four times more effective in absorbing juice than was a bare human hand (see Westergaard & Fragaszy, 1987).
Experiment 3 Method Design. Experiment 3 was designed to examine the use of probing tools in the acquisition and consumption of desired food. A container filled with sweet syrup was provided in the animals' home cage along with materials from which probing tools could be fashioned. The container had a narrow opening through which the animals could insert their fingers but not the entire width of their hands. This task was designed to examine behavior functionally analogous to the use and manufacture of probing implements by chimpanzees, capuchin monkeys, and lion-tailed macaques (Goodall, 1964; Westergaard, 1988; Westergaard & Fragaszy, 1987). Subjects and apparatus. The subjects were the 5 infant baboons used in Experiment 2. Experiment 3 began 3 weeks after the onset of Experiment 2. The apparatus was a plastic container ( 1 2 x 1 2 x 1 7 cm) with a single narrow opening (1.5 cm in diameter). Procedure. Experiment 3 was conducted during 14 daily 1-hr sessions. At the onset of each session, the container was secured to the cage mesh and filled with maple-flavored pancake syrup. Ten strips of browse were then distributed on the floor of the home cage. Browse strips were 10-50 cm in length and consisted of sticks and twigs taken from local shrubs. Data were collected by an observer who noted each instance in which an animal used browse to obtain syrup from the container.
Results All the baboons quickly learned to obtain syrup by inserting their fingers into the opening of the apparatus and by licking spilled drops from the side of the container. Over the course of this experiment, 4 baboons used browse tools to extract
and consume syrup. Jack, Karl, Ivan, and Jenny first used tools to extract syrup in Sessions 2, 3, 6, and 11, respectively. Kim did not use browse to extract syrup from the container but did pick up and lick tools that were discarded by other animals. Table 3 provides a quantitative summary of the baboons' use of probing tools. The baboons used tools to obtain syrup in 58 bouts (dips per bout, M = 1.8). The baboons used leaves in 54 bouts (dips per bout, M = 1.9) and twigs in 4 bouts (dips per bout, M = 1.8). Typically, a baboon picked up a leaf or twig, brushed it across the top of the container, poked the leaf or twig into the opening, removed the syrup-covered instrument, and placed the object directly into its mouth. A notable difference between the use of probing and sponging tools was the increased dexterity required for the use of delicate browse tools to extract syrup from the narrow opening of the probing apparatus. The baboons acquired the use of probing tools through patterns of active experimentation similar to those noted for the use of sponging tools in Experiment 2. The acquisition pattern shown by Ivan provides an illustrative example. During Sessions 1-5, Ivan obtained some syrup by inserting his fingers into the opening of the apparatus, by licking discarded tools, and by stealing tools from other animals. He also rubbed objects near the opening of the apparatus in five instances (one instance occurred in Session 2 and four instances occurred in Session 5). During Session 5, Ivan inserted a leaf and a food biscuit into the apparatus, but he did not remove the objects and did not obtain syrup from these actions. Ivan rubbed browse near the opening of the apparatus in two instances in Session 6 (at 10 min and 50 min, 35 s). At 51 min, 15 s, of Session 6, Ivan approached the apparatus and rubbed a leaf against the inner rim of the container's opening and into the syrup. Ivan then brought the object to his mouth and licked the sweet liquid from it. Ivan successfully inserted a second probe into the apparatus at 23 min, 39 s, of Session 9. In the time that elapsed between his first and second probing dips, Ivan rubbed browse near the opening of the apparatus in 25 separate instances. As in the previous experiment, the baboons sometimes modified objects before they used them as tools, used individual tools in succession, and in some cases stole syrup-covered probes from unwilling conspecifics.
Table 3 Experiment 3: Summary of Probing Activities Leaves
Twigs
Total
No. Mean No. Mean No. Mean Subject bouts dips/bout bouts dips/bout bouts dips/bout Ivan 15 2.4 0 2.4 15 Jack 11 11 1.5 0 1.5 — 1 1 Jenny 1.0 1.0 0 — 27 4 Karl 31 1.6 1.6 1.8
Kim
0
Total
54
— 1.9
0
— 1.8
0
58
Note. Probing activities are given by material used.
— 1.8
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GREGORY CHARLES WESTERGAARD
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Discussion Infant baboons aged 6-8 months used objects as containers, drinking utensils, and sponges in the context of play with no extrinsic reward (Experiment 1). In follow-up studies the baboons used tools to extract sweet liquids from an apparatus designed to accommodate sponging and probing behavior (Experiments 2 and 3). This report is the first to describe flexible combinatorial manipulation and spontaneous use of tools in infant baboons. The range of combinatorial responses observed in the baboons exceeds that which has been described for other 6- to 8-month-old nonhuman primates. These data are particularly noteworthy in view of studies that have indicated that immature cercopithecine monkeys do not adequately understand object relations that facilitate the use of tools (Antinucci, Spinozzi, Visalberghi, & Volterra, 1982; Parker, 1977). Baboons in nature consume a broad variety of foods and sometimes extract their prey while foraging. The observation that infant baboons flexibly combine objects is consistent with the hypothesis that an evolutionary history of omnivorous extractive foraging is associated with the use of tools (Parker & Gibson, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1987). The results of this study and of previous studies that have demonstrated spontaneous use of tools by lion-tailed macaques provide further evidence for continuity among primates in the expression of combinatorial manipulation. Note than in a previous study the use of tools was not observed in a group of three juvenile mandrills (Mandrillus sphinx) during a 2-month period in which the animals were exposed to a probing apparatus (Westergaard, 1988). This finding suggests that a species closely related to baboons may not be capable of the manipulative sophistication reported in this investigation. Numerous field studies have been conducted with baboons, and few have provided descriptions of sophisticated manipulative actions like those that have been described for sympatric chimpanzees. The results of this study indicate that baboons can develop extensive sensorimotor propensities in a captive environment where objects of various sizes and shapes are freely available. These data are consistent with the idea that captive living provides monkeys with extended opportunities for free play and that the developmental influence of free play may enable some nonhuman primates to express their behavioral potential for combinatorial manipulation more fully (Beck, 1980; Bruner, 1972). Future studies that examine the proximate influences of captive living on the development of manipulative behavior in monkeys and apes will prove useful for evaluating this hypothesis. In summary, the data reported in this article demonstrate flexible combinatorial manipulation and spontaneous use of tools by infant baboons. The baboons' behavior was similar in form, function, and ontogeny to sophisticated manipulative behavior that has been described previously for chimpanzees, capuchin monkeys, and lion-tailed macaques (see Goodall, 1964; McGrew, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1987). The baboons combined objects and used tools in a variety of contexts, used different materials as tools, used individual tools repeatedly, and modified objects so that
they served more effectively as tools. The results of this study are consistent with hypotheses that (a) an evolutionary history of omnivorous extractive foraging is associated with spontaneous use of tools and (b) free play in an object-enriched captive environment may facilitate combinatorial manipulation in nonhuman primates. Research into the development of spontaneous tool use in infant baboons will facilitate further understanding of the psychological mechanisms associated with combinatorial manipulation in nonhuman primates. References Antinucci, F., Spinozzi, G., Visalberghi, E., & Volterra, V. (1982). Cognitive development in a Japanese macaque (Macaco fuscatd). Annali dell Istituto Superiore di Sanitd, 18, 177-183. Beck, B. B. (1980). Animal tool behavior: The use and manufacture of tools by animals. New York: Garland. Bhat, H. R. (1990). Additional information on tool use by lion-tailed macaques. Lion-Tails: Lion-Tailed Macaque Newsletter, 7, 6. Bruner, J. S. (1972). Nature and uses of immaturity. American Psychologist, 27, 687-708. Chevalier-Skolnikoff, S. (1989). Spontaneous tool use and sensorimotor intelligence in Cebus compared with other monkeys and apes. Behavioral and Brain Sciences, 12, 561-627. Goodall, J. (1964). Tool-using and aimed throwing in a community of free-living chimpanzees. Nature, 201, 1264-1266. Hamilton, W. J., Ill, Buskirk, R. E., & Buskirk, W. H. (1978). Environmental determinants of object manipulation by chacma baboons (Papio ursinus) in two Southern African environments. Journal of Human Evolution, 7, 205-216. Infant Primate Research Laboratory. (1986). Research protocols guide. Seattle, WA: Child Development and Mental Retardation Center. Johnson, T. J. M. (1985). Lion-tailed macaque behavior in the wild. In P. G. Heltne (Ed.), The lion-tailed macaque: Status and conservation (pp. 41-63). New York: Alan R. Liss. Joubert, A., & Vauclair, J. (1986). Reaction to novel objects in a troop of Guinea baboons: Approach and manipulation. Behaviour, 96, 92-104. McGrew, W. C. (1977). Socialization and object-manipulation of wild chimpanzees. In S. Chevalier-Skolnikoflf& F. E. Poirier (Eds.), Primate bio-social development: Biological, social, and ecological determinants (pp. 261-288). New York: Garland. Parker, S. (1977). Piaget's sensorimotor series in an infant macaque: A model for comparing unstereotyped behavior and intelligence in human and nonhuman primates. In S. Chevalier-Skolnikoff & F. E. Poirier (Eds.), Primate bio-social development: Biological, social, and ecological determinants (pp. 43-112). New York: Garland. Parker, S. T., & Gibson, K. R. (1977). Object manipulation, tool use, and sensorimotor intelligence as feeding adaptations in Cebus monkeys and great apes. Journal of Human Evolution, 6, 623-641. Parker, S. T., & Poti, P. (1990). The role of innate motor patterns in ontogenetic and experiential development of intelligent use of sticks in Cebus monkeys. In S. T. Parker & K. R. Gibson (Eds.), "Language" and intelligence in monkeys and apes: Comparative developmental perspectives (pp. 219-243). New York: Cambridge University Press. Sackett, G. P. (1972). Exploratory behavior of rhesus monkeys as a function of rearing experience and sex. Developmental Psychology, 6, 260-270. Teleki, G. (1974). Chimpanzee subsistence technology: Materials and skills. Journal of Human Evolution, 3, 574-594.
OBJECT MANIPULATION IN INFANT BABOONS
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Westergaard, G. C. (1988). Lion-tailed macaques (Macaco silenus) manufacture and use tools. Journal of Comparative Psychology, 102, 152-159. Westergaard, G. C. (1989). Infant baboons spontaneously use an object to obtain distant food. Perceptual and Motor Skills, 68, 558. Westergaard, G. C., & Fragaszy, D. M. (1985). Effects of manipulatable objects on the activity of captive capuchin monkeys (Cebus apella). Zoo Biology, 4, 317-327. Westergaard, G. C., & Fragaszy, D. M. (1987). The manufacture and
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use of tools by capuchin monkeys (Cebus apella). Journal of Comparative Psychology, 101, 159-168. Whiten, A. (1988, July). Acquisition of foraging strategies in infant olive baboons. Paper presented at the XII Congress of the International Primatological Society, Brasilia. Received July 5, 1991 Revision received November 22, 1991 Accepted November 25, 1991 •
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Object Manipulation and the Use of Tools by Infant Baboons (Papio cynocephalus anubis]
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Gregory Charles Westergaard University of Washington Infant baboons (Papio cynocephalus anubis) in a captive peer group used objects as containers, drinking utensils, and sponges in the context of play. The baboons later used paper, browse, and other materials as tools to extract sweet liquids from apparatus designed to accommodate sponging and probing behavior. The results of this study demonstrate flexible combinatorial manipulation and spontaneous use of tools by infant baboons. These data are consistent with hypotheses that (a) an evolutionary history of omnivorous extractive foraging is associated with the use of tools and (b) free play in an object-enriched captive environment may facilitate combinatorial manipulation in nonhuman primates.
Object manipulation and the use of tools by nonhuman primates have held scientific interest for many years (for a review, see Chevalier-Skolnikoff, 1989). The propensity for sophisticated manipulative behavior in great apes and capuchin monkeys has led to considerable speculation about the evolutionary origins of underlying sensorimotor strategies. Parker and Gibson (1977) and Chevalier-Skolnikoff (1989) have proposed a hypothesis of phylogenetic discontinuity in the expression of combinatorial manipulation. They have argued that flexible combinatorial manipulation evolved separately in the ancestors of great apes and capuchin monkeys but not in the ancestors of other nonhuman primates, as a result of selection pressures that favored omnivorous extractive foraging. Research with lion-tailed macaques (Macaca silenus) has indicated that combinatorial manipulation may be more prevalent among nonhuman primates than was proposed by Parker and Gibson (1977) or Chevalier-Skolnikoff (1989). In an empirical study lion-tailed macaques in captive social groups spontaneously manufactured and used tools to extract sweet syrup from an apparatus designed to accommodate probing behavior. The macaques prepared tools by detaching sticks from larger branches and sometimes modified their tools further by subtracting projecting stubs, leaves, and bark (Westergaard, 1988). Lion-tailed macaques are now known to use tools in nature (Bhat, 1990), where they consume a broad variety of foods and sometimes extract their prey (Johnson, 1985). These reports have provided further evidence for continuity among primates in the expression of combinatorial manipulation and are consistent with the hypothesis that an evolutionary history of omnivorous extractive foraging is
associated with the use of tools (Westergaard, 1988; Westergaard & Fragaszy, 1987). The finding that lion-tailed macaques manufacture and use tools has led me to speculate that other omnivorous Old World monkeys have the potential to express similar manipulative sophistication. Baboons in nature extract and consume a broad variety of foods (Hamilton, Buskirk, & Buskirk, 1978; Whiten, 1988) and use tools in contexts that include agonistic encounters, hammering, leverage, raking, and self-grooming (summarized in Beck, 1980). However, Beck (1980) cited only two anecdotal descriptions of baboons' use of sticks as feeding implements and no reports of baboons' use of sponging material to absorb and consume water. The observation that wild baboons do not readily use sponging or probing tools is of particular interest in view of their close association with tool-using chimpanzees (Teleki, 1974). Chevalier-Skolnikoff(1989) noted that although baboons use tools in several contexts, the use of tools by individual animals remains stereotyped over time and is not consistent with the flexible combinatorial manipulation that has been noted for great apes and capuchin monkeys. To the best of my knowledge, the youngest monkeys that have used tools were capuchins (Cebus apella) aged 10-14 months (Westergaard & Fragaszy, 1987). Immature capuchins developed the use of tools over a period of several weeks as a result of trial-and-error experimentation (also see Parker & Poti, 1990). A similar acquisition pattern was noted for immature lion-tailed macaques, although these animals did not use tools until the age of 24 months (Westergaard, 1988). A recent study has indicated that baboons may also be able to use tools at a very early age (Westergaard, 1989). Infant baboons aged 7-11 months spontaneously learned to acquire food by maneuvering a plastic rod into a distant food container. Although that report described a specific and somewhat narrow instance of manipulative sophistication, it does suggest that baboons are manipulatively precocious and indicates the need for further research with additional subjects in varied and generalized tasks. The purpose of this research was to examine object manipulation and the use of tools by captive infant baboons (Papio cynocephalus anubis). Previous research has indicated that infant baboons engage in frequent and diverse manipulative
This research was conducted at the University of Washington's Infant Primate Research Laboratory and was supported by National Institutes of Health Grants HDO2274 and RR00166. I thank C. Menuhin-Hauser, M. Amorette, M. Sputnik, D. Fragaszy, and G. Sackett for support and encouragement throughout all phases of this research. Correspondence concerning this article should be addressed to Gregory Charles Westergaard, who is now at the Laboratory of Comparative Ethology, National Institutes of Health Animal Center, Building 112, Elmer School Road, Poolesville, Maryland 20837.
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OBJECT MANIPULATION IN INFANT BABOONS
actions (Joubert & Vauclair, 1986) and use objects as rakes to secure otherwise inaccessible food (Westergaard, 1989). In this investigation three experiments were conducted in the home cage of a socially housed peer group. In Experiment 1, three sets of stimulus objects were provided to facilitate the discovery of novel object relations in the context of play with no extrinsic reward. In Experiments 2 and 3, apparatus designed to accommodate sponging and probing behavior were provided along with material from which the baboons could fashion appropriate tools. The rationale was to examine the use of tools in contexts that were functionally analogous to those that have been described for chimpanzees, capuchin monkeys, and lion-tailed macaques (see Chevalier-Skolnikoff, 1989; Goodall, 1964; McGrew, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1985, 1987). On the basis of the hypothesis that an evolutionary history of omnivorous extractive foraging correlates positively with the expression of toolusing propensities, it was predicted that the baboons would engage in sophisticated manipulative actions similar to those that have been reported for other nonhuman primates that have shown a strong tendency to use tools.
Experiment 1 Method Design. Experiment 1 was designed to examine combinatorial manipulation by infant baboons in the context of play. Three sets of stimulus objects were introduced into the home cage of a socially housed peer group. In Condition 1, objects were selected to facilitate the use of containers and drinking utensils. In Condition 2, objects were selected to facilitate the use of sponges. In Condition 3, the objects used in Conditions 1 and 2 were provided to facilitate simultaneous use of containers and sponges. Subjects and apparatus. Subjects were 3 infant baboons (Papio cynocephalus papio) that ranged in age from 25-33 weeks. They included 2 males (Ivan and Jack; both 25 weeks of age at the onset of this experiment) and 1 female (Heidi; 33 weeks of age). The baboons were medically healthy members of the University of Washington Infant Primate Research Laboratory "Infant Save" program, which provides nursery rearing of infants that would not survive if left in their natal social group. These include prematurely delivered infants, infants rejected by their mothers, and infants who are injured during aggressive interactions. The baboons in this study were reared by human caretakers under standard laboratory conditions, which include daily periods of socialization to prevent isolation rearing effects (see Research Protocols Guide, Infant Primate Research Laboratory, 1986; Sackett, 1972). At the time of this experiment, the baboons were housed together in an indoor cage (1.5 m wide x 1.3 m high x 2.1 m deep). Food and water were available ad libitum. Stimulus objects were rubber balls (5 cm in diameter), plastic cups (13 cm high, 10 cm in diameter at the opening, and 8 cm in diameter at the base), paper towels (24 x 28 cm), and a plastic tub (29 x 38 x 14 cm). Procedure. One-hr observation sessions were conducted daily over a period of 3'/2 weeks. Nine sessions were conducted in Conditions 1 and 3, and six sessions were conducted in Condition 2. At the onset of each session, stimulus objects were distributed on the floor of the animals' home cage. Three balls and three cups were used in Condition 1. In Condition 2, a tub partially filled with water (to a depth of about 10 cm) and 10 paper towels were used. A plastic pipe
(30 cm in length) was skewered through the paper towels and hung in the cage about 1 m from the tub. In Condition 3, the objects used in Conditions 1 and 2 were distributed simultaneously in the manner just described. Throughout the experiment, data were collected by an observer who noted the absolute frequency of combinatorial manipulation in which one object was placed in direct relation to another, such as when an animal placed an object into a container or used a towel as a sponge to absorb and consume water. Qualitative notes and videotape provided supporting details. Analysis. Combinatorial manipulations were organized into four mutually exclusive and exhaustive categories: (a) container, an action of an animal's placing one solid object inside another; (b) drinking utensil, a two-step sequence of an animal's holding a plastic cup under the water spigot and then drinking directly from the partially filled object; (c) sponge, a two-step sequence of an animal's placing a paper towel into the plastic tub and then removing and chewing the water-laden object; and (d) other, such as an animal's placing an object in direct contact with the water spigot (causing water to freely flow) or using a plastic cup as a scoop to displace water from the plastic tub.
Results The baboons used objects as containers in 157 instances (see Table 1). Heidi and Ivan first used containers during Condition 1 (in Sessions 3 and 7, respectively), and Jack first used a container during Condition 3 (Session 3). The baboons placed several types of objects into plastic cups, including rubber balls, paper towels, and food biscuits. The baboons used cups to concurrently contain as many as two objects and repeated the action of inserting and removing an object as many as three times in one uninterrupted behavioral sequence. The baboons used paper towels as sponges to absorb and consume water in 64 instances. Heidi and Ivan first used a sponge in Condition 2 (Session 1). Jack did not use sponges during this experiment but did obtain water by drinking directly from the tub, by picking up discarded sponges from the cage floor, and by stealing sponges from the other animals. The baboons repeated the sponging action as many as four times in one interrupted behavioral sequence. Heidi was the only baboon that used a plastic cup as a drinking utensil. She first exhibited this behavior during Condition 1. Twelve min after the onset of Session 1, Heidi picked up a plastic cup from the cage floor, jumped to a perch, held the cup under the water spigot, brought the open end of the
Table 1 Experiment 1: Absolute Frequency of Combinatorial Manipulations Across Conditions Combinatorial manipulation Subject Container Sponge Heidi 68 29 Ivan 42 35 Jack 47 0 Total
157
64
Drinking utensil Other Total Rate/hr
8 0 0
18 14 0
123 91 47
32
261
5.1 3.8 2.0
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GREGORY CHARLES WESTERGAARD
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cup to her mouth, and drank directly from it. Heidi repeated this action as many as two times in one uninterrupted behavioral sequence. The baboons expressed other combinatorial manipulations in 32 instances. The animals placed objects in direct contact with the water spigot in 18 instances. Seventeen instances of this behavior were observed in Heidi, and one instance of this behavior was observed in Ivan. The animals used cups as scoops to displace water from the tub in 14 instances. One instance of this behavior was observed in Heidi, and 13 instances of this behavior were observed in Ivan.
Experiment 2 Method Design. This two-phase experiment was designed to examine spontaneous use of sponges in the acquisition and consumption of sweet juice. In Phase 1, an open container partially filled with apple juice was provided in the baboons' home cage along with paper towels that could be used as sponges to absorb and consume the liquid. In Phase 2, three containers were used to facilitate greater access to the food source among socially subordinate subjects. These tasks were designed to examine behavior functionally analogous to the use of sponging materials by chimpanzees and capuchin monkeys (see McGrew, 1977; Westergaard & Fragaszy, 1987). Subjects and apparatus. The subjects were 5 infant baboons. They included the 2 males used in Experiment 1 (Ivan and Jack; both 29 weeks of age at the onset of Experiment 2), an additional male (Karl; 24 weeks of age), and two females (Jenny and Kim; 26 and 24 weeks of age, respectively). Karl, Jenny, and Kim were reared and cared for under the conditions described in Experiment 1. The apparatus included plastic containers (12 x 12 x 17 cm with a 10 cm opening on top) and paper towels (24 x 28 cm). Procedure. Phase 1 was conducted during 12 daily 1-hr sessions. At the onset of each session, a container was partially filled with apple juice (to a depth of about 6 cm) and secured to the mesh inside the home cage. A plastic pipe was skewered through 10 paper towels and hung in the cage about 1 m from the tub. Data were collected by an observer who noted each instance in which an animal inserted a towel into the container, removed the towel, and consumed juice. Phase 2 was conducted during 9 daily 1-hr sessions. The procedure was similar to that used in Phase 1 except that three containers partially filled with apple juice were secured side-by-side to the cage mesh. During Phase 2, data were collected only for those animals that did not use sponges in Phase 1.
Results All the baboons quickly learned to obtain juice by reaching into the container with their bare hands. Three baboons used paper towels as sponges to absorb and consume juice during Phase 1. Ivan and Jack first used sponges in Session 1, and Karl first used a sponge in Session 9. The other two baboons (Jenny and Kim) first used sponges during Phase 2 (in Sessions 2 and 5, respectively), when additional containers of juice were available. Table 2 provides a quantitative summary of sponging activities. The baboons used paper towels as sponges in a total of 344 bouts (dips per bout, M = 3.3). Typically, a baboon picked up a paper towel and placed it into the juice container,
Table 2 Experiment 2: Summary of Sponging Activities Subject Ivan Jack Jenny Karl Kim
No. bouts
Mean dips/bout
88 156 61 27 12
2.0 4.8 6.2 4.9 1.7
Total
344
3.3
Note. Date reported for Ivan, Jack, and Karl were collected when one apple juice container was in the home cage. Data reported for Jenny and Kim were collected when three apple juice containers were in the home cage.
allowed the towel to soak (sometimes for 30 s or longer), removed the soaked object, and placed it directly into its mouth. The baboons consumed the juice by repeatedly chewing the soaked paper towels. The baboons acquired the use of sponges through patterns of active experimentation. The acquisition patterns exhibited by Ivan and Karl provide illustrative examples. Before his initial sponging dip, Ivan repeatedly reached into the container with his bare hand, and in one instance (3 min, 4 s into Session 1), he picked up a towel and rubbed it along the outside rim of the container's opening. Ivan quickly discarded the towel and did not obtain juice from this action. A few minutes later (8 min, 46 s), Ivan approached the apparatus and chewed the container's rim. He then turned his back to the container, picked up a paper towel, turned back to the apparatus, and rubbed the towel along the inside rim of the container's opening and downward into the juice. He then removed the wet towel from the apparatus and chewed it. At 15 min, 36 s, Ivan rubbed another paper towel against the rim of the apparatus, but he did not obtain juice from this action. Ivan completed his second sponging dip several minutes later (at 22 min, 9 s). Karl, on the other hand, acquired the use of sponges in a pattern that developed over several test sessions. During the first two sessions, Karl infrequently visited the apparatus. Karl visited the apparatus with increased frequency in Sessions 3-8, and in 11 instances he removed discarded sponges from inside the juice container. Karl chewed these soaked objects, but he did not reinsert them into the apparatus. During Session 8, Karl approached the apparatus and rubbed paper towels along the rim of the container's opening in three separate instances. Karl did not obtain juice as a result of these actions. Karl completed his initial sponging dip at 14 min into Session 9. At 13 min, 50 s, Karl picked up a towel and approached the apparatus. He then wiped the towel downward along the inside of the container and into the juice. He then removed the wet towel and chewed it. Karl picked up another towel and completed his second and third sponging dips about 1 min later. The baboons engaged in several sponging behaviors that have been noted previously for chimpanzees and capuchin monkeys (McGrew, 1977; Westergaard & Fragaszy, 1987). The baboons manufactured sponges by detaching towels from the plastic pipe, by reshaping towels with their hands and teeth, by subtracting excess portions of towel, and by combin-
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OBJECT MANIPULATION IN INFANT BABOONS
ing two or more towels in an apparent attempt to construct a more absorbent sponge. On occasion several animals used individual tools in succession, and the animals frequently stole portions of towel from unwilling conspecifics. The baboons displayed response generalization toward alternate sponging materials during informal follow-up sessions when they readily used banana chips, corn husks, cloth, and paper confetti to absorb and consume juice. The baboons gained two advantages by using paper towels rather than bare hands to absorb and consume juice. First, the use of paper towels enabled the baboons to transport juice away from the frantic activity that surrounded the apparatus. This strategy was especially useful to socially subordinate baboons because it enabled these animals to consume juice somewhat free from the harassment of conspecifics. Second, the use of paper towels enabled the baboons to absorb more juice per dip than was possible through the use of a bare hand. I conducted an informal test of the effectiveness of these two modes of absorption in order to evaluate this hypothesis. First, I inserted my hand into a container of water 10 times and then measured the volume of liquid that had been displaced. I then repeated this procedure holding an appropriately shaped paper towel. On the basis of this test, I determined that a hand with a paper towel was about four times more effective in absorbing juice than was a bare human hand (see Westergaard & Fragaszy, 1987).
Experiment 3 Method Design. Experiment 3 was designed to examine the use of probing tools in the acquisition and consumption of desired food. A container filled with sweet syrup was provided in the animals' home cage along with materials from which probing tools could be fashioned. The container had a narrow opening through which the animals could insert their fingers but not the entire width of their hands. This task was designed to examine behavior functionally analogous to the use and manufacture of probing implements by chimpanzees, capuchin monkeys, and lion-tailed macaques (Goodall, 1964; Westergaard, 1988; Westergaard & Fragaszy, 1987). Subjects and apparatus. The subjects were the 5 infant baboons used in Experiment 2. Experiment 3 began 3 weeks after the onset of Experiment 2. The apparatus was a plastic container ( 1 2 x 1 2 x 1 7 cm) with a single narrow opening (1.5 cm in diameter). Procedure. Experiment 3 was conducted during 14 daily 1-hr sessions. At the onset of each session, the container was secured to the cage mesh and filled with maple-flavored pancake syrup. Ten strips of browse were then distributed on the floor of the home cage. Browse strips were 10-50 cm in length and consisted of sticks and twigs taken from local shrubs. Data were collected by an observer who noted each instance in which an animal used browse to obtain syrup from the container.
Results All the baboons quickly learned to obtain syrup by inserting their fingers into the opening of the apparatus and by licking spilled drops from the side of the container. Over the course of this experiment, 4 baboons used browse tools to extract
and consume syrup. Jack, Karl, Ivan, and Jenny first used tools to extract syrup in Sessions 2, 3, 6, and 11, respectively. Kim did not use browse to extract syrup from the container but did pick up and lick tools that were discarded by other animals. Table 3 provides a quantitative summary of the baboons' use of probing tools. The baboons used tools to obtain syrup in 58 bouts (dips per bout, M = 1.8). The baboons used leaves in 54 bouts (dips per bout, M = 1.9) and twigs in 4 bouts (dips per bout, M = 1.8). Typically, a baboon picked up a leaf or twig, brushed it across the top of the container, poked the leaf or twig into the opening, removed the syrup-covered instrument, and placed the object directly into its mouth. A notable difference between the use of probing and sponging tools was the increased dexterity required for the use of delicate browse tools to extract syrup from the narrow opening of the probing apparatus. The baboons acquired the use of probing tools through patterns of active experimentation similar to those noted for the use of sponging tools in Experiment 2. The acquisition pattern shown by Ivan provides an illustrative example. During Sessions 1-5, Ivan obtained some syrup by inserting his fingers into the opening of the apparatus, by licking discarded tools, and by stealing tools from other animals. He also rubbed objects near the opening of the apparatus in five instances (one instance occurred in Session 2 and four instances occurred in Session 5). During Session 5, Ivan inserted a leaf and a food biscuit into the apparatus, but he did not remove the objects and did not obtain syrup from these actions. Ivan rubbed browse near the opening of the apparatus in two instances in Session 6 (at 10 min and 50 min, 35 s). At 51 min, 15 s, of Session 6, Ivan approached the apparatus and rubbed a leaf against the inner rim of the container's opening and into the syrup. Ivan then brought the object to his mouth and licked the sweet liquid from it. Ivan successfully inserted a second probe into the apparatus at 23 min, 39 s, of Session 9. In the time that elapsed between his first and second probing dips, Ivan rubbed browse near the opening of the apparatus in 25 separate instances. As in the previous experiment, the baboons sometimes modified objects before they used them as tools, used individual tools in succession, and in some cases stole syrup-covered probes from unwilling conspecifics.
Table 3 Experiment 3: Summary of Probing Activities Leaves
Twigs
Total
No. Mean No. Mean No. Mean Subject bouts dips/bout bouts dips/bout bouts dips/bout Ivan 15 2.4 0 2.4 15 Jack 11 11 1.5 0 1.5 — 1 1 Jenny 1.0 1.0 0 — 27 4 Karl 31 1.6 1.6 1.8
Kim
0
Total
54
— 1.9
0
— 1.8
0
58
Note. Probing activities are given by material used.
— 1.8
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GREGORY CHARLES WESTERGAARD
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Discussion Infant baboons aged 6-8 months used objects as containers, drinking utensils, and sponges in the context of play with no extrinsic reward (Experiment 1). In follow-up studies the baboons used tools to extract sweet liquids from an apparatus designed to accommodate sponging and probing behavior (Experiments 2 and 3). This report is the first to describe flexible combinatorial manipulation and spontaneous use of tools in infant baboons. The range of combinatorial responses observed in the baboons exceeds that which has been described for other 6- to 8-month-old nonhuman primates. These data are particularly noteworthy in view of studies that have indicated that immature cercopithecine monkeys do not adequately understand object relations that facilitate the use of tools (Antinucci, Spinozzi, Visalberghi, & Volterra, 1982; Parker, 1977). Baboons in nature consume a broad variety of foods and sometimes extract their prey while foraging. The observation that infant baboons flexibly combine objects is consistent with the hypothesis that an evolutionary history of omnivorous extractive foraging is associated with the use of tools (Parker & Gibson, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1987). The results of this study and of previous studies that have demonstrated spontaneous use of tools by lion-tailed macaques provide further evidence for continuity among primates in the expression of combinatorial manipulation. Note than in a previous study the use of tools was not observed in a group of three juvenile mandrills (Mandrillus sphinx) during a 2-month period in which the animals were exposed to a probing apparatus (Westergaard, 1988). This finding suggests that a species closely related to baboons may not be capable of the manipulative sophistication reported in this investigation. Numerous field studies have been conducted with baboons, and few have provided descriptions of sophisticated manipulative actions like those that have been described for sympatric chimpanzees. The results of this study indicate that baboons can develop extensive sensorimotor propensities in a captive environment where objects of various sizes and shapes are freely available. These data are consistent with the idea that captive living provides monkeys with extended opportunities for free play and that the developmental influence of free play may enable some nonhuman primates to express their behavioral potential for combinatorial manipulation more fully (Beck, 1980; Bruner, 1972). Future studies that examine the proximate influences of captive living on the development of manipulative behavior in monkeys and apes will prove useful for evaluating this hypothesis. In summary, the data reported in this article demonstrate flexible combinatorial manipulation and spontaneous use of tools by infant baboons. The baboons' behavior was similar in form, function, and ontogeny to sophisticated manipulative behavior that has been described previously for chimpanzees, capuchin monkeys, and lion-tailed macaques (see Goodall, 1964; McGrew, 1977; Westergaard, 1988; Westergaard & Fragaszy, 1987). The baboons combined objects and used tools in a variety of contexts, used different materials as tools, used individual tools repeatedly, and modified objects so that
they served more effectively as tools. The results of this study are consistent with hypotheses that (a) an evolutionary history of omnivorous extractive foraging is associated with spontaneous use of tools and (b) free play in an object-enriched captive environment may facilitate combinatorial manipulation in nonhuman primates. Research into the development of spontaneous tool use in infant baboons will facilitate further understanding of the psychological mechanisms associated with combinatorial manipulation in nonhuman primates. References Antinucci, F., Spinozzi, G., Visalberghi, E., & Volterra, V. (1982). Cognitive development in a Japanese macaque (Macaco fuscatd). Annali dell Istituto Superiore di Sanitd, 18, 177-183. Beck, B. B. (1980). Animal tool behavior: The use and manufacture of tools by animals. New York: Garland. Bhat, H. R. (1990). Additional information on tool use by lion-tailed macaques. Lion-Tails: Lion-Tailed Macaque Newsletter, 7, 6. Bruner, J. S. (1972). Nature and uses of immaturity. American Psychologist, 27, 687-708. Chevalier-Skolnikoff, S. (1989). Spontaneous tool use and sensorimotor intelligence in Cebus compared with other monkeys and apes. Behavioral and Brain Sciences, 12, 561-627. Goodall, J. (1964). Tool-using and aimed throwing in a community of free-living chimpanzees. Nature, 201, 1264-1266. Hamilton, W. J., Ill, Buskirk, R. E., & Buskirk, W. H. (1978). Environmental determinants of object manipulation by chacma baboons (Papio ursinus) in two Southern African environments. Journal of Human Evolution, 7, 205-216. Infant Primate Research Laboratory. (1986). Research protocols guide. Seattle, WA: Child Development and Mental Retardation Center. Johnson, T. J. M. (1985). Lion-tailed macaque behavior in the wild. In P. G. Heltne (Ed.), The lion-tailed macaque: Status and conservation (pp. 41-63). New York: Alan R. Liss. Joubert, A., & Vauclair, J. (1986). Reaction to novel objects in a troop of Guinea baboons: Approach and manipulation. Behaviour, 96, 92-104. McGrew, W. C. (1977). Socialization and object-manipulation of wild chimpanzees. In S. Chevalier-Skolnikoflf& F. E. Poirier (Eds.), Primate bio-social development: Biological, social, and ecological determinants (pp. 261-288). New York: Garland. Parker, S. (1977). Piaget's sensorimotor series in an infant macaque: A model for comparing unstereotyped behavior and intelligence in human and nonhuman primates. In S. Chevalier-Skolnikoff & F. E. Poirier (Eds.), Primate bio-social development: Biological, social, and ecological determinants (pp. 43-112). New York: Garland. Parker, S. T., & Gibson, K. R. (1977). Object manipulation, tool use, and sensorimotor intelligence as feeding adaptations in Cebus monkeys and great apes. Journal of Human Evolution, 6, 623-641. Parker, S. T., & Poti, P. (1990). The role of innate motor patterns in ontogenetic and experiential development of intelligent use of sticks in Cebus monkeys. In S. T. Parker & K. R. Gibson (Eds.), "Language" and intelligence in monkeys and apes: Comparative developmental perspectives (pp. 219-243). New York: Cambridge University Press. Sackett, G. P. (1972). Exploratory behavior of rhesus monkeys as a function of rearing experience and sex. Developmental Psychology, 6, 260-270. Teleki, G. (1974). Chimpanzee subsistence technology: Materials and skills. Journal of Human Evolution, 3, 574-594.
OBJECT MANIPULATION IN INFANT BABOONS
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Westergaard, G. C. (1988). Lion-tailed macaques (Macaco silenus) manufacture and use tools. Journal of Comparative Psychology, 102, 152-159. Westergaard, G. C. (1989). Infant baboons spontaneously use an object to obtain distant food. Perceptual and Motor Skills, 68, 558. Westergaard, G. C., & Fragaszy, D. M. (1985). Effects of manipulatable objects on the activity of captive capuchin monkeys (Cebus apella). Zoo Biology, 4, 317-327. Westergaard, G. C., & Fragaszy, D. M. (1987). The manufacture and
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use of tools by capuchin monkeys (Cebus apella). Journal of Comparative Psychology, 101, 159-168. Whiten, A. (1988, July). Acquisition of foraging strategies in infant olive baboons. Paper presented at the XII Congress of the International Primatological Society, Brasilia. Received July 5, 1991 Revision received November 22, 1991 Accepted November 25, 1991 •
Neuropsychology to Be an APA Journal In January 1993, Neuropsychology, which has been published by the Educational Publishing Foundation (a subsidiary publishing program of the American Psychological Association), will be published by the American Psychological Association. The Publications and Communications Board of the APA has appointed Nelson Butters as editor of Neuropsychology. As of January 1,1992, manuscripts should be submitted to Nelson Butters Chief, Psychology Service (116B) Department of Veterans Affairs Medical Center 3350 La Jolla Village Drive La Jolla,CA 92161 Manuscripts considered by the incoming editor will be published beginning in the January 1993 issue. Submitted manuscripts should fall within the following new editorial policy statement: The mission of Neuropsychology is to foster (a) basic research, (b) the integration of basic and applied research, and (c) improved practice in the field of neuropsychology, broadly conceived. The primary function of Neuropsychology is to publish original, empirical papers in the field. Occasionally, scholarly reviews and theoretical papers will also be published—all with the goal of promoting empirical research on the relation between brain and human cognitive, emotional, and behavioral function. Sought are submissions of human experimental, cognitive, and behavioral research with implications for neuropsychological theory and practice. Papers that increase our understanding of neuropsychological functions in both normal and disordered states and across the lifespan are encouraged. Applied, clinical research that will stimulate systematic experimental, cognitive, and behavioral investigations as well as improve the effectiveness, range, and depth of application is germane. Neuropsychology seeks to be the vehicle for the best research and ideas in the field.
