Please cite this article in press as: Whiten et al., Transmission of Multiple Traditions within and between Chimpanzee
Groups, Current Biology (2007), doi:10.1016/j.cub.2007.05.031
Current Biology 17, 1–6, June 19, 2007 ª2007 Elsevier Ltd All rights reserved

DOI 10.1016/j.cub.2007.05.031

ReportTransmission of Multiple Traditions
within and between Chimpanzee Groups
Andrew Whiten,1,* Antoine Spiteri,1 Victoria Horner,1,2
Kristin E. Bonnie,2 Susan P. Lambeth,3Steven J. Schapiro,3 and Frans B.M. de Waal2
1
Centre for Social Learning and Cognitive Evolution and
Scottish Primate Research Group
School of Psychology
University of St Andrews
St Andrews KY16 9JP
United Kingdom
2
Living Links
Yerkes National Primate Research Center
Emory University
Atlanta, Georgia 30329
3
Department of Veterinary Sciences
The University of Texas M. D. Anderson Cancer Center
Bastrop, Texas 78602

Summary
Field reports provide increasing evidence for local
behavioral traditions among fish, birds, and mammals[1–7]. These findings are significant for evolutionary
biology because social learning affords faster adaptation than genetic change and has generated new(cultural) forms of evolution [8–10]. Orangutan andchimpanzee field studies [3, 4, 11–13] suggest thatlike humans [14, 15], these apes are distinctive among
animals in each exhibiting over 30 local traditions.
However, direct evidence is lacking in apes and, withthe exception of vocal dialects [16, 17], in animals
generally for the intergroup transmission that would
allow innovations to spread widely and become evolutionarily significant phenomena. Here, we provide
robust experimental evidence that alternative foraging
techniques seeded in different groups of chimpanzees
spread differentially not only within groups but seriallyacross two further groups with substantial fidelity.
Combining these results with those from recentsocial-diffusion studies in two larger groups [18–20]
offers the first experimental evidence that a nonhumanspecies can sustain unique local cultures, each constituted by multiple traditions. The convergence of
these results with those from the wild implies a richness in chimpanzees’ capacity for culture, a richness
that parsimony suggests was shared with our common ancestor.
Results and Discussion
Numerous local variations in the behavior patterns ofwild chimpanzees and orangutans have been inferred
to be cultural variants, transmitted through observational learning [3, 4, 11–13]. However, this inference
relies heavily on circumstantial evidence that alternative*Correspondence: a.whiten@st-andrews.ac.uk

genetic or environmental explanations are implausible.
Field experiments could in principle provide a morerobust test that putative traditions are truly sociallylearned, but logistic and ethical considerations have
prevented exploratory interventions from employing
controls to clearly discriminate the effects of socialfrom individual learning [21, 22]. We have instead investigated chimpanzees’ cultural capacities by conducting
large-scale, controlled social-diffusion experimentswith captive groups.
To investigate between-group transmission, we useda unique chimpanzee population that includes six
groups of 8–11 individuals at Bastrop, Texas (Table S1in the Supplemental Data available online), where eachgroup has visual access to its neighbors (Figure 1).
Two complex tool-use problems (‘‘probe task’’ and‘‘turn-ip’’), each designed to make solution throughindividual exploration unlikely but solvable by two quite
different techniques (Figure 2), were presented separately to each group for a 2 hr baseline period. Most
chimpanzees explored these objects in the baseline
period (Table S2), but none successfully extracted thefood items they had seen dropped inside.
For each task in turn, a single chimpanzee from groupB1 was then trained to use one of the two techniques toextract food, out of sight of her group. An individual fromgroup B4 was likewise trained to use the alternativetechnique. Each model was then returned to its compound, with the apparatus available to the whole groupat location 1 (Figure 1). Interactions with the apparatus
were recorded on video for analysis. A total of 1643 successful (food-gaining) operations of the probe task werewatched by a median of six individuals sitting within 1 m(range one to nine individuals). For the turn-ip, a medianof four individuals (range one to nine) watched 5360 successes. Thus, all members of a group sometimes
formed a tightly packed cluster of observers within
1 m around an actively foraging chimpanzee.
By contrast with the absence of task solutions in thebaseline phase, after observing the initial model, a second individual successfully solved the probe task after
28 min in group B1 and after 15 min in group B4. During
8 hr of exposure spread over 3 days, all but three individuals mastered the probe task. To test for preferential
adoption of the model’s technique, we computeda ‘‘%stab’’ index (%stab = 100 3 stab/[stab + slide]).
The %stab index was significantly greater in group B1(median 100%), seeded with the stab technique, thanin B4, seeded with the alternative slide technique (median 0.0%; Mann-Whitney U test, U = 2, p = 0.016:
Figure 3A; Table S3 lists sample sizes). For the twostep turn-ip task, an individual other than the model
was successful after 87 min in group B1 and 36 min ingroup B4. During 24 hr of exposure spread over
8 days, all but two individuals gained food from the turnip, although four completed only the second of the two
required actions after a group mate had performed thefirst (Figure 3). To test for social transmission, wePlease cite this article in press as: Whiten et al., Transmission of Multiple Traditions within and between Chimpanzee
Groups, Current Biology (2007), doi:10.1016/j.cub.2007.05.031
Current Biology
2

Figure 1. Compound Configuration
Each external compound, diameter 21 m, accommodates 8–11
chimpanzees. Successive presentation locations of foraging tasks
next to barred windows are marked 1–5. Chimpanzees in B2 andB5 were able to watch foraging techniques applied by their neighbors at location 2 before attempting the task themselves at location
3; the same was later true for chimpanzees in B3 and B6 with respect
to locations 4 and 5, respectively.

computed ‘‘%ratchet’’ (%ratchet = 100 3 [ratchet thenslide]/[ratchet then slide] + [turn then press]). This index
was significantly greater in group B1, seeded with theratchet-then-slide technique (median 100%) than in
B4, seeded with the turn-then-press technique (median
0%; Mann-Whitney U test, U = 0, p < 0.001; Figure 3B).
Once half of a group’s members were successful,each foraging task was presented to the same groupat a second location where the neighboring group could
observe work on it through their windows at a distanceof approximately 3 m (B1 and B2) or 5 m (B4 and B5; Figure 1), for six 30 min sessions. This procedure was later
repeated for a third group in each case (B3 and B6,
respectively). Operations of the probe task in one groupwere watched by a median of four individuals (range
1–11), and operations of the turn-ip were watched bya median of three individuals (range 1–11) in the neighboring group (see Table S3 for details). Each of theseobserving groups in turn was then given access to theforaging device at its own window (locations 3 and 5 inFigure 1). Each technique was transmitted with highfidelity across these groups (Figure 3). Both measuresof differential use of techniques, %stab and %ratchet,were significantly greater in B2 than in B5 and greaterin B3 than in B6 (p always < 0.02; Table S3).
This is the first evidence in a nonhuman species for the
between-group diffusion of socially learned behavior
patterns necessary for significant spreading of traditions. As in prior within-group diffusion experiments(18–20), individual corruption events occurred in eachgroup, raising the prospect that the contrasts between
traditions would progressively erode; yet instead, eachseeded variant remained clearly dominant in the corresponding final group, suggesting a conformity effect(Figure 3). The social diffusion of experimentally seeded,alternative foraging techniques across over 20 individuals in each case is unprecedented in the literature on
animal social learning (reviewed in [19]). These results
hold substantial import for recent debates concerning
the inherent weaknesses of nonexperimental evidence

Figure 2. Probing and Turn-Ip Foraging Tasks(A) Probing task, stab technique. By pushing to one side a small button, chimpanzees can open a doorway in the top surface and insert
a tool to stab food items.
(B) Probing task, slide technique. Once a hatch door is raised, a flat
tool can be inserted, pushing food items along the floor and out ofa tunnel on the opposite side, with the food then rolling to chimpanzees down a ramp (not shown) beneath.
(C) Turn-ip task. Food items dropped into the pipe are trapped until
the disc is rotated to align hole 1 with the pipe. This can be achieved
either by directly turning the front edge of the disc protruding
through a slit (method ‘‘turn’’) or by repeatedly pulling a ratchet
handle on the top surface (method ‘‘ratchet’’). Once the food drops,
it can be released either by pressing down a handle to lift plate aligning holes 2 and 3 (method ‘‘press’’) or pushing a sliding handle thataligns holes 2 and 4 (method ‘‘slide’’).

for cultural variations among wild apes [23–25]. We
conclude that chimpanzees have a demonstrable
capacity for fidelity in social learning across multiple
groups, consistent with the hypothesis that regional
behavior patterns in Africa have spread through culturaltransmission [4, 12]. In the wild, the context for intergroup transmission would be unlikely to directly mirrorthat of our experiments because of intergroup antagonism, but opportunities for the observational learning
we have documented arise naturally through the transfer
of females between groups [4, 22, 26]. Indeed, our results suggest that investigating intergroup transmission
by translocation of skilled individuals into naive groupsPlease cite this article in press as: Whiten et al., Transmission of Multiple Traditions within and between Chimpanzee
Groups, Current Biology (2007), doi:10.1016/j.cub.2007.05.031
Transmission of Traditions in Chimpanzees
3

Figure 3. Spread of Alternative Traditions across Two Series of Three Groups
Arrows indicate direction of between-groups information transfer.
(A) Probing task, initiated by trained models KE in group B1 (stab method) and JU in group B4 (slide technique). Chimpanzees in group B2 wereable to observe techniques employed by group B1 and in turn were observed by group B3. Groups B4, B5, and B6 had parallel observational
opportunities. Individual chimpanzees are labeled with two-character codes and arranged by order of successful task solution. Each bar shows
the number of stab (dark) and slide (light) actions by each chimpanzee, capped at their first 100 successes.
(B) Turn-ip task, initiated by trained models KE in group B1 (ratchet-then-slide technique) and XE in group B4 (turn-then-press technique).
Between-group observation opportunities were as for the probing task. Each bar shows the number of successful ratchet (light green), slide(midgreen), ratchet-then-slide (dark green), turn (light blue), press (midblue), and turn-then-press (dark blue) actions by each chimpanzee.
Each category is capped at the first 100 successes (for overall statistics, see Table S2 in the Supplemental Data). Slide could exceed ratchet,and press could exceed spin, where one individual exploited the prior performance by another individual of the first of the two actions necessary
to attain food.

would be a valuable further step, even if a much moredifficult one to arrange in practice.
Combining these results with those recently obtainedin three separate diffusion experiments with two larger
groups of chimpanzees now allows us to address thecontroversial hypothesis that chimpanzees are able tosustain multiple, diverse behavioral traditions aptly
described as local cultures, by analogy with the humancase [9, 10, 14, 15]. These data are illustrated in Figure 4,
which collates the results of three experiments conducted at the Field Station of the Yerkes National Primate Research Center (respectively labeled ‘‘Doorian,’’‘‘panpipes,’’ and ‘‘token’’ experiments after the manipulanda involved [18–20] with those from the intergroupexperiments (turn-ip and probe task) conducted at Bastrop and reported in detail above. Each of these studies

has separately demonstrated a new aspect of culturaltransmission in animals. Here, we integrate them todocument local cultures defined by multiple behavioral
variations, to our knowledge the first demonstration ofthis capacity in a nonhuman species. Thus, the Yerkes
FS1 culture is characterized by lifting open the Doorian,poking a tool in the panpipes to gain food, and using
a bucket for depositing tokens, whereas the Yerkes
FS2 culture typically involves sliding open the Doorian,lifting an obstacle to release food from the panpipes,
and posting tokens down a pipe. Similarly, the Bastrop-West culture (groups B1–B3) is defined by stabbing
in the probe task and applying the ratchet-then-slide
technique to the turn-ip, whereas in Bastrop-East (B4–
B6), chimpanzees typically use two different techniques
for these tasks. In addition, the spontaneous emergencePlease cite this article in press as: Whiten et al., Transmission of Multiple Traditions within and between Chimpanzee
Groups, Current Biology (2007), doi:10.1016/j.cub.2007.05.031
Current Biology
4

Figure 4. Four ‘‘Cultures’’ Each Defined by Multiple Different Traditions
Yerkes-FS1 culture (Doorian-lift, token-to-bucket, panpipe-poke, and handclasp traditions) is shown on the upper left; Yerkes-FS2 culture(Doorian-slide, token-to-pipe, panpipe-lift, and no-handclasp traditions) is shown on the upper right; Bastrop-West (B1–B3) culture (probeby-stab, turn-ip ratchet-then-slide traditions) is shown on the lower left; and Bastrop-East (B4–B6) culture (probe-by-slide, turn-ip turn-thenpress traditions) is shown on the lower right. Each rectangle denotes a chimpanzee, identified by a two-character label in the corresponding
column. Initial, trained models are denoted by thick borders. Numbers represent order of successful acquisition of each task. Order was notreliably known for handclasp grooming and was predetermined in the transmission-chain Doorian-task study charted in the upper Yerkes frame.
In the lower Yerkes and Bastrop frames, acquisition order in the first task (panpipe at Yerkes, turn-ip at Bastrop) is numbered serially left toright, with order for other tasks labeled for the same chimpanzees. Color boxes indicate the following: Doorian task [19]: red = lift, yellow =slide; panpipe task [18]: red = poke, pink = lift; token study [20]: orange = bucket, cream = pipe; handclasp [27]: brown = handclasp; probing:
purple = stab, lilac = slide; and turn-ip: blue = ratchet-then-slide, green = turn-then-press. For each chimpanzee, the dominant response isshown, with those performing one of the alternatives at between 25%–75% of the total indicated here as 50%. Individuals performing only
half the turn-ip task are indicated by a half bar. A cross indicates those individuals who never performed a task.

and spread of handclasp grooming, a locally varying
custom known in the wild in which grooming partners
clasp hands overhead [27], has been documented indetail in FS1 yet has not occurred in FS2 [28]. This provides a fourth tradition discriminating the Yerkes cultures (Figure 4).
The transmission of these different traditions in multiple groups offers the unique opportunity to investigate
whether general principles apply to the diffusion process. We begin such investigation here by examining
whether consistencies exist in the order in which techniques diffused through groups. The order in which individuals in each group mastered the probe and turn-ip
tasks was significantly correlated in groups B2 (r =0.74, n = 7, and p = 0.037), B3 (r = 0.84, n = 9, and p =0.001), and B6 (r = 0.95, n = 8, and p < 0.001), and thecorrelation was high and positive for all six groups(Table S4) (binomial test, p = 0.04). By contrast, the correlation between order of acquisition in the panpipes
and token tasks at Yerkes was negative and nonsignificant (FS1, r = 20.50, n = 9, NS; FS2, r = 20.54 n = 6, NS;such correlations cannot be tested for the Doorianstudy, because this required direct experimental control
over order of acquisition, nor for the handclasp study,
which spanned several years involving significant

demographic changes). Together, the Bastrop and
Yerkes results suggest that similar general principles
govern tasks of the same kind (tool-based foraging in
the case of the probe task and turn-ip) but different factors come into play for tasks as different as the panpipes(tool-based foraging) and tokens (arbitrary conventionsof object use). The consistency between similar tasks
and variations between different ones suggest there ismuch scope for future investigation of the social dynamics and other factors determining the spread of experimentally seeded traditions.
Our Bastrop experiments are the first to demonstrate
the spread of alternative traditions from group to groupin a nonhuman species. Whether the underlying sociallearning mechanism is imitation or some other process
is a separate question requiring different kinds of experiment. In a recent study [29], we found that chimpanzees
did not learn from a ‘‘ghost’’ condition in which our panpipes task was operated remotely with no chimpanzee
involved, challenging a current view that chimpanzees
learn by ‘‘emulation,’’ in which they focus only on the results of actions, as opposed to imitating the actions
themselves [23]. Our ghost experiments indicate thatchimpanzees are instead motivated to learn specificallyfrom a conspecific doing the action of interest [29].

Please cite this article in press as: Whiten et al., Transmission of Multiple Traditions within and between Chimpanzee
Groups, Current Biology (2007), doi:10.1016/j.cub.2007.05.031
Transmission of Traditions in Chimpanzees
5

Whatever the social-learning mechanisms involved in
the studies reported here, our findings demonstrate
a capacity for within-group and between-group transmission of the fidelity required to explain the spread of
putative chimpanzee traditions across regions of Africa[4, 12]. In addition, we have shown that these animals
can sustain local cultures constituted by multiple behavior patterns of different kinds, as apes have been hypothesized to do in the wild [3, 4, 7, 11–13]. These results
suggest that humans’ prodigious capacity for culture is
likely to have evolved from a foundation in the common
ancestor we share with chimpanzees that in these respects already represented the most developed culturalabilities among animals. Our seeding of alternative behavioral techniques in different groups has proven to
be a powerful method in investigating such phenomena;
extending it in future comparative studies with otherspecies opens the prospect of a comprehensive pictureof the evolutionary foundations of culture in the animal
kingdom.
Experimental Procedures
Subjects‘‘Bastrop’’ chimpanzees were housed at the University of Texas M.D.
Anderson Cancer Center near Bastrop, Texas, and are described inTable S1. Yerkes subjects are fully described in [18] and [19]. Highranking females were selected as the first two trained models so thatthey would maintain control of the task and initially perform a highlevel of competent demonstrations.
Materials
Foraging devices and alternative foraging techniques are describedin Figure 2 and in detail in the Supplemental Data.
ProceduresOnce each initial model in B1 and B4 was reunited with her group, anobservation phase was maintained in which the apparatus was withdrawn if chimpanzees other than the model took the tool, until all in
the group had witnessed five or more successful uses of the tool. In
the subsequent open diffusion phase, all chimpanzees were allowed
access to tools and foraging tasks. The first such trial was 30 min,and this was followed by five 5 hr trials. For the between-groups
transfer phase that began once half the first group were successful,six 30 min observation periods were each followed by a 30 min trial
with the inexperienced group. Alternation of 30 min periods between
groups then continued until a new model appeared in the inexperienced group, at which point 5 hr sessions continued with this group.
A detailed account of procedures is included in the Supplemental
Data.
Interobserver Reliability
Reliability for each of the critical six behavior patterns (Figure 3) isshown in the Supplemental Data. Given the gross differences intechnique, reliability was high, with a median of 99% agreement
between coders.
Statistics
Choice of statistical procedures is described in the Supplemental
Data.
Ethical Treatment of Animals
Both the Yerkes and Bastrop facilities are fully accredited by the
Association for Assessment and Accreditation of Laboratory Animal
Care—International. Training of chimpanzees as models was
through human demonstration followed by positive-reward shaping
as necessary.
Supplemental Data
Additional Experimental Procedures, Author Contributions, and fivetables are available at http://www.current-biology.com/cgi/content/
full/17/12/---/DC1/.

Acknowledgments
Studies reported here were supported by the Biotechnology andBiological Sciences Research Council and Leverhulme Trust (UK),
National Institutes of Health (NIH) grants to the Yerkes National
Primate Research Center, and the Living Links Center of Emory University. A.W. was supported by a Royal Society Leverhulme Trust
Senior Fellowship. The Bastrop colony is supported by NIH/NCRR
through cooperative agreement with the NIH National Center for Research Resources. We thank L. Hopper for interobserver-agreement
coding, A. Burnley and E. Thiele for expert help in construction of
foraging devices, and M. Dindo, T. Fitch, L. Hopper, R. Kendal,
and W.C. McGrew for comments on the manuscript.
Received: April 6, 2007
Revised: May 9, 2007
Accepted: May 10, 2007
Published online: June 7, 2007
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