Sheet1
Background:
What is the aim of the study/Hypothesis
2-3 lines what is they are trying to do in comparison to previous studies?
Experiment Set up
Sample size
Number of groups
Experimental group condition
Control group condition
What was the difference in the control and experimental group condition
Why was group 3 not considered?
Figure 2 A and 2B
What is X axis Y axis
What is the observation among all groups
What are these stats numbers saying for each group
frequency, t = 3.26, df = 483,
P < 0.002, r = 0.147; duration, t = 9.21, df = 483, P < 0.001, r = 0.387,
N = 29; see Fig. 2)
(frequency: t = 2.52, df = 483, P = 0.012, r = 0.114;
duration: t = 9.72, df = 483, P < 0.001, r = 0.405, N = 29).
Figure 3 A and 3B
What is X axis Y axis
What is the observation among all groups
Description of bar plots
Wilcoxon
signed-rank test, both frequency and duration: P < 0.0001; N = 29
Figure 4A and 4B
What is X axis Y axis
What is the observation among all groups
Description of bar plots
(Kruskal-Wallis
rank sum test: Chi square = 8.43, df = 2, P = 0.015;
Group_1” (Wilcoxon rank sum test:
W = 16, P = XXXXXXXXXXand “Group_2” (W = 11, P = 0.005).
Figure 5A and 5B and 5C
What is X axis Y axis
What is the observation among all groups
Description of bar plots
Chi square 8.28,
df = 2, P = 0.016, N = 29; Fig. 5A; Group_1 versus Group_4:
W = 13.5, P = 0.026; Group_2 versus Group_4: P = NS; Group_1
versus Group_2: W = 24.5, P = 0.011;
Chi square = 10.28, df = 2, P = 0.012, N = 29; Fig. 5B; Group_1 versus
Group_4: W = 13, P = 0.020; Group_2 versus Group_4: P = NS;
Group_1 versus Group_2: W = 21, P = 0.008; for details on the
individual level, see fig. S5).
Intriguingly, both
these group-dependent prosocial patterns mapped onto the chimpanzees’
respective group-level social tolerance, a factor known to
facilitate the emergence of prosocial and cooperative behaviors
(Chi square 2 = 16.83, df = 2, P < 0.001; Fig. 5C)
Figure 6
What is the graph depicting
What are those color bands , nodes and lines
What conclusion was made based on this graph
Some questions for which I need answers.
What is the group level social tolerance experiment and what was the result
Need not describe the procedure, I need to understand the objective and the result
What was Cohen’s k calculation; drinking spoils
Conclusion
What was the conclusion? Why did one group behave significantly? What is author trying to suggest in terms of human behavior?
Science Journals — AAAS
van Leeuwen et al., Sci. Adv. 2021; 7 : eabc XXXXXXXXXXFe
uary 2021
S C I E N C E A D V A N C E S | R E S E A R C H A R T I C L E
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S O C I A L S C I E N C E S
Chimpanzees behave prosocially in
a group-specific manne
Edwin J. C. van Leeuwen1,2,3,4*, Sarah E. DeTroy4,5, Stephan P. Kaufhold6, Clara Dubois5,
Sebastian Schütte6, Josep Call1, Daniel B. M. Haun4,5
Chimpanzees act cooperatively in the wild, but whether they afford benefits to others, and whether their tenden-
cy to act prosocially varies across communities, is unclear. Here, we show that chimpanzees from neighboring
communities provide valuable resources to group members at personal cost, and that the magnitude of their
prosocial behavior is group specific. Provided with a resource-donation experiment allowing free (partner) choice,
we observed an increase in prosocial acts across the study period in most of the chimpanzees. When group mem-
ers could profit (test condition), chimpanzees provided resources more frequently and for longer durations than
when their acts produced inaccessible resources (control condition). Strikingly, chimpanzees’ prosocial behavior
was group specific, with more socially tolerant groups acting more prosocially. We conclude that chimpanzees
may purposely behave prosocially toward group members, and that the notion of group-specific sociality in non-
human animals should crucially inform discussions on the evolution of prosocial behavior.
INTRODUCTION
Humans regularly confer benefits on others, even at a cost to them-
selves (1, 2). The extent to which humans act prosocially has been
suggested to be at the root of humans’ unique social abilities, argu-
ably unparalleled in the animal kingdom (2–5). In an attempt to
explore the evolutionary trajectory of this prosocial behavior, chim-
panzees, as one of humans’ closest living relatives, have been studied
extensively in prosocial paradigms, both in the wild and under con-
trolled settings in captivity. To date, however, the evidence con-
cerning chimpanzee prosociality remains equivocal.
Prosocial behavior has been defined as “any behavior voluntarily
performed by one individual to benefit another” (6–8). On the one
hand, evidence exists that wild chimpanzees spontaneously engage
in prosocial behavior, for instance, in the form of food sharing,
third-party consolation after fights, and infant adoption (9, 10).
These observations have been co
oborated by experimental para-
digms in which chimpanzees readily helped experimenters obtain
an out-of-reach object (11) and transfe
ed useful objects to con-
specifics without receiving anything in return (12, 13), although the
extent to which instrumental helping in apes can be deemed “pro-
social” is cu
ently a hot topic of debate [see (14–16)]. On the other
hand, evidence from so-called prosocial choice tests [see (8)] has
culminated in the conclusion that “chimpanzees are indifferent to
the welfare of others” (17). In these studies, in the experimental
condition, one individual of a preselected dyad is presented with a
choice between delivering a prefe
ed food item only to themselves
and to themselves and their partner, in contrast to a control condition,
in which the surplus food item would be delivered to an empty cage
(instead of their partner). If the chimpanzee chooses the “both-food”
option more than the “alone-food” option in the experimental, but
not the control, condition, the choice is deemed prosocial. In gener-
al, these tests have yielded negative outcomes: Chimpanzees do not
seem to confer benefits on conspecifics at no cost to themselves
[(17–20); cf. (21, 22)].
Typically, the experimental paradigms used to investigate proso-
ciality in chimpanzees have prioritized experimental rigor at the
expense of ecological validity. To capture natural social dynamics
etween chimpanzees, in this case, prosocial behavior, we pro-
pose to move the experimental paradigm from indoor testing with
human-imposed selection of chimpanzee dyads to outdoor testing
with free partner choice [also see (8, 23, 24)]. Moreover, on the basis
of recent findings evidencing substantial variation in social dynam-
ics across multiple groups of chimpanzees (25, 26), we conjecture
that the endeavor to investigate chimpanzee prosociality has been
lind-sighted by single-group testing (27), with incongruent findings
potentially attributable to intergroup differences between chimpanzee
communities.
Here, we introduce a new methodological approach, which re-
veals large-group differences in prosocial behavior among chim-
panzees (Pan troglodytes). Instead of giving chimpanzees isolated
and time-restricted choices, we presented prosocial opportunities
for extended periods of time to three groups of chimpanzees living
under naturalistic conditions at a Zambian sanctuary (N = 94; table
S1 and fig. S1). During this time, the chimpanzees had access to a
utton that, when pushed, released juice from a distant fountain,
enefiting any conspecifics present at the fountain, but not the
pusher themselves. We investigated whether chimpanzees would
increasingly push for each other over time, whether they would
push more often when the result of their acts would benefit group
members compared to nobody (i.e., a control condition), and, given
the recent evidence for substantial intraspecific variation in chim-
panzee sociality (25, 26), whether group identity would moderate
the extent and selectivity of chimpanzees’ prosocial behavior.
To familiarize the chimpanzees with the experimental paradigm,
we implemented the test setup in their enclosures and let them freely
explore all possible contingencies. Each group was presented with
1University of St Andrews, Westburn Lane, KY16 9JP St Andrews, Scotland. 2Behav-
ioral Ecology and Ecophysiology Group, Department of Biology, University of Antwerp,
Universiteitsplein 1, 2610 Wilrijk, Belgium. 3Centre for Research and Conservation,
Royal Zoological Society of Antwerp, K. Astridplein 26, B 2018 Antwerp, Belgium.
4Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103
Leipzig, Germany. 5Leipzig Research Centre for Early Child Development & Depart-
ment for Early Child Development and Culture, Faculty of Education, Leipzig Uni-
versity, Jahnallee XXXXXXXXXX, Germany. 6Department of Cognitive Science, University
of California, San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA.
*Co
esponding author. Email: XXXXXXXXXX
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The Authors, some
ights reserved;
exclusive licensee
American Association
for the Advancement
of Science. No claim to
original U.S. Government
Works. Distributed
under a Creative
Commons Attribution
NonCommercial
License 4.0 (CC BY-NC).
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van Leeuwen et al., Sci. Adv. 2021; 7 : eabc XXXXXXXXXXFe
uary 2021
S C I E N C E A D V A N C E S | R E S E A R C H A R T I C L E
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the test setup for ±10 two-hour familiarization sessions before the
actual experiment started. During these sessions, whenever a chim-
panzee touched the button, the fountain was covertly activated
from outside the enclosure. These interventions progressed from
eleasing juice from the fountain whenever a chimpanzee placed a
foot or hand on the button to releasing juice only upon observing
ehaviors that resembled accurate pushing. The purpose of these
familiarization sessions was to maximize the number of chimpan-
zees becoming knowledgeable of the workings of the setup. To fur-
ther increase the likelihood of tapping into intentional prosocial
ehavior, subsequently, in the analyses of the test sessions (±30 two-
hour sessions per group during which no interventions from the
experimenters took