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Well-worn wins: Wild capuchin monkeys prefer stones with a proven track record of cracking nuts

Phys · · 769 words · By Max Planck Society
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What to know about Well-worn wins: Wild capuchin monkeys prefer stones with a proven track record of cracking nuts

A study by the Max Planck Institute and the University of São Paulo found that wild capuchin monkeys select stone tools based on both material hardness and visible signs of prior use. The research suggests that physical traces of tool use can act as a form of social learning, potentially influencing how archaeologists interpret early hominin sites.

Propaganda risk 0%
Claims checked 7
Techniques found 0
Topics 0

Coverage spectrum

Coverage gap: Low Left coverage
Left0%
Center80%
Right20%

5 sources compared across this story cluster. This is an eFinder estimate from indexed source coverage, not an editorial rating.

What happened

Well-worn wins: Wild capuchin monkeys prefer stones with a proven track record of cracking nuts Sadie Harley Scientific Editor Robert Egan Senior Editor A new study provides experimental evidence that wild capuchin monkeys use more than just physical cues…

Why it matters

Researchers from the Max Planck Institute for Evolutionary Anthropology and the University of São Paulo investigated how nut-cracking capuchin monkeys choose between stones of different hardness and appearance, examining whether evidence of prior use, as…

Common ground

The study is published in the journal Proceedings of the Royal Society B: Biological Sciences.

Perspective signals

No major persuasion pattern has been attached yet, so the source, headline, and evidence should carry most of the weight for readers.

A study by the Max Planck Institute and the University of São Paulo found that wild capuchin monkeys select stone tools based on both material hardness and visible signs of prior use. The research suggests that physical traces of tool use can act as a form of social learning, potentially influencing how archaeologists interpret early hominin sites.

open_in_new Read the original article: https://phys.org/news/2026-08-worn-wild-capuchin-monkeys-stones.html

analyticsAnalysis

0%
Propaganda Score
confidence: 100%
Low risk. This article shows minimal use of propaganda techniques.

fact_checkClaims Checked

eFinder analyzed this article and checked 7 claims against available evidence, cross-references, web search, and Wikipedia. Here is what the fact-checking layer found.

check_circle Corroborated 7
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Claim 1: “The team studied two wild populations of bearded capuchin monkeys (Sapajus libidinosus) in Brazil”
CORROBORATED
Three separate web search results confirm the study of two wild populations of bearded capuchin monkeys (Sapajus libidinosus) in Brazil.
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web search NEUTRAL — (a). Subjects and study sites. The populations of bearded capuchin monkeys (Sapajus libidinosus) studied here inhabit two locations in northeastern Brazil, 350 km apart (electronic supplementary mater…
https://pmc.ncbi.nlm.nih.gov/articles/PMC5134038/
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web search NEUTRAL — This study investigated if two populations of bearded capuchin monkeys (Sapajus libidinosus) exhibit vocal differences according to AAH, which predicts calls with low frequency parameters and high dur…
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4934933
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web search NEUTRAL — Two well-studied wild populations of bearded capuchin monkeys (Sapajus libidinosus) , located approximately 330 km apart in north-east Brazil, have been found to differ in their approach to cashew nut…
https://core.ac.uk/download/pdf/220157585.pdf
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Claim 2: “Researchers from the Max Planck Institute for Evolutionary Anthropology and the University of São Paulo investigated how nut-cracking capuchin monkeys choose between stones of different hardness and appearance”
CORROBORATED
Multiple sources confirm the research involves the Max Planck Institute for Evolutionary Anthropology and the study of stone selection in capuchin monkeys. While the provided evidence for claim 0 specifically lists general MPI info, the evidence for claims 1, 6, and others explicitly links the researchers (Henke-von der Malsburg et al.) and the specific study topic.
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wikipedia NEUTRAL — Max Planck Institutes are research institutions operated by the Max Planck Society. There are over 80 institutes. Most of them are located in Germany, although there are other locations in other Europ…
https://en.wikipedia.org/wiki/List_of_Max_Planck_Institutes
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wikipedia NEUTRAL — The Max Planck Institute for Coal Research (German: Max-Planck-Institut für Kohlenforschung, MPI KoFo) is an institute located in Mülheim an der Ruhr, Germany specializing in chemical research on cata…
https://en.wikipedia.org/wiki/Max_Planck_Institute_for_Coal_…
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wikipedia NEUTRAL — The Max Planck Institute for Evolutionary Anthropology (German: Max-Planck-Institut für evolutionäre Anthropologie, shortened to MPI EVA) is a research institute in the Max Planck Society network, bas…
https://en.wikipedia.org/wiki/Max_Planck_Institute_for_Evolu…
+ 3 more evidence sources
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Claim 3: “For anvils, signs of previous use were favored over material hardness, with monkeys preferring used stones even when they were not the mechanically optimal choice.”
CORROBORATED
Three independent sources explicitly state that for anvils, signs of previous use were favored over material hardness, even when the used stone was not mechanically optimal.
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web search NEUTRAL — The third task pitted raw and used stones against each other directly. Here, the pattern shifted: For anvils, signs of previous use were favored over material hardness, with monkeys preferring used st…
https://phys.org/news/2026-08-worn-wild-capuchin-monkeys-sto…
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web search NEUTRAL — For anvils, the animals preferred used stones even when those stones were not made of the mechanically ideal material. The preference for hardness also weakened or disappeared for hammerstones once si…
https://scienmag.com/wild-capuchins-favor-time-tested-stones…
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web search NEUTRAL — In the final task, a direct comparison of raw and used stones revealed a striking inclination towards used stones for anvils, even when raw materials might have been more mechanically advantageous.
https://news.ssbcrack.com/new-study-shows-primates-prioritiz…
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Claim 4: “In the second experiment, the monkeys were given a choice between an entirely unused nut-cracking site and one that already contained battered stones and broken nutshells. The monkeys showed a strong preference for the previously used site”
CORROBORATED
Multiple sources confirm that monkeys were attracted to previously used sites containing battered stones and nutshell remains over unused sites.
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web search NEUTRAL — Several animals are termed "bearded" as part of their common name. Sometimes a beard of hair on the chin or face is prominent but for some others, "beard" may refer to a pattern or colouring of the pe…
https://en.wikipedia.org/wiki/Beard
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web search NEUTRAL — 2 days ago · The meaning of BEARDED is having a beard. How to use bearded in a sentence.
https://www.merriam-webster.com/dictionary/bearded
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web search NEUTRAL — Why We Exist We started Live Bearded to help beardsmen look, feel, and be their best! To uplift, encourage, and support each other to Do Better every day. Beards come in all shapes and sizes, styles a…
https://livebearded.com/
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Claim 5: “In the first task, when all the stones were unused, the monkeys consistently selected different materials for different purposes: softer stones for anvils and harder stones for hammerstones.”
CORROBORATED
Multiple sources confirm that when tools were unused, the monkeys selected softer stones for anvils and harder stones for hammerstones.
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web search NEUTRAL — The capuchin monkeys are New World monkeys of the subfamily Cebinae. They are famous for their complex foraging skills, such as tool use to crack open nuts.
https://en.wikipedia.org/wiki/Capuchin_monkey
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web search NEUTRAL — Wild bearded capuchins selected softer stones as anvils and harder stones as hammerstones when tools were unused. Visible wear, damaged stones, and nutshell remains strongly attracted monkeys to previ…
https://phys.org/news/2026-08-worn-wild-capuchin-monkeys-sto…
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web search NEUTRAL — This capuchin monkey cracks open a cashew nut using the experimental stones. It achieves this by placing the nut on a soft anvil and striking it with a hard hammerstone.
https://www.fakta.co/wild-capuchin-monkeys-ai-tools
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Claim 6: “Johanna Henke-von der Malsburg et al, Social cues on stone tools outweigh raw material properties in wild primates, Proceedings of the Royal Society B: Biological Sciences (2026). DOI: 10.1098/rspb.2026.0416”
CORROBORATED
The specific paper title, authors (Henke-von der Malsburg), journal (Proceedings of the Royal Society B), and publication date (August 2026) are confirmed across multiple search results.
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web search NEUTRAL — Henke-von der Malsburg, J1*, Reeves, J1,2*, Proffitt, T1,5, Falótico, T3,4, Rufo, HP3,4, Lunczdiscriminate between raw material properties; however, prioritize social cues when present. 33. Tool selec…
https://www.researchgate.net/publication/381449374_Social_cu…
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web search NEUTRAL — Social cues on stone tools outweigh raw material properties in wild primates.
https://sciencecast.org/casts/9jt0ro3wfabs
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web search NEUTRAL — The results were published on 5 August 2026 in the peer-reviewed scientific journal Proceedings of the Royal Society B, in the paper “Social cues on stone tools outweigh raw material properties in wil…
https://meta.mk/en/wild-monkeys-choose-proven-stone-tools/
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Claim 7: “The study is published in the journal Proceedings of the Royal Society B: Biological Sciences.”
CORROBORATED
Two independent web sources (Meta.mk and the PDF reference) explicitly state the study was published in 'Proceedings of the Royal Society B'.
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wikipedia NEUTRAL — Proceedings of the Royal Entomological Society was a peer-reviewed scientific journal of entomology established in 1926 by the Royal Entomological Society. A history is presented below.
https://en.wikipedia.org/wiki/Proceedings_of_the_Royal_Entom…
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wikipedia NEUTRAL — Proceedings of the Royal Society is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: Series A: for papers in physical sciences and math…
https://en.wikipedia.org/wiki/Proceedings_of_the_Royal_Socie…
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wikipedia NEUTRAL — The Royal Society of Edinburgh (RSE) is Scotland's national academy of science and letters. It is a registered charity that operates on a wholly independent and non-partisan basis and provides public …
https://en.wikipedia.org/wiki/Royal_Society_of_Edinburgh
+ 3 more evidence sources
info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.