Editing Chimpanzee (section)

==Intelligence==
{{further|Primate cognition}}
[[File:Man&chimpbrains.png|thumb|left|alt=Drawing of human and chimpanzee skull and brain|Human and chimpanzee skull and brain. Diagram by [[Paul Gervais]] from ''Histoire naturelle des mammifères'' (1854).]]
Chimpanzees display numerous signs of intelligence, from the ability to remember symbols<ref name="symbol"/> to cooperation,<ref name="recruit"/> tool use,<ref name="Boesch1993"/> and varied [[Great ape language|language capabilities]].<ref name="GAT"/> They are among species that have passed the [[mirror test]], suggesting [[self-awareness]].<ref>{{cite journal |first=D. |last=Povinelli |author2=de Veer, M. |author3=Gallup Jr., G. |author4=Theall, L. |author5=van den Bos, R. |title=An 8-year longitudinal study of mirror self-recognition in chimpanzees (''Pan troglodytes'') |journal=Neuropsychologia |volume=41 |issue=2 |pages=229–334 |doi=10.1016/S0028-3932(02)00153-7 |pmid=12459221 |year=2003|s2cid=9400080}}</ref> In one study, two young chimpanzees showed retention of mirror self-recognition after one year without access to mirrors.<ref>{{cite journal |last1=Calhoun |first1=S. |last2=Thompson |first2=R. L. |name-list-style=amp |year=1988 |title=Long-term retention of self-recognition by chimpanzees |journal=American Journal of Primatology |volume=15 |issue=4 |pages=361–365 |doi=10.1002/ajp.1350150409 |pmid=31968884 |s2cid=84381806}}</ref> Chimpanzees have been observed to use insects to treat their own wounds and those of others. They catch them and apply them directly to the injury.<ref>{{cite journal|last1=Mascaro|first1=A.|last2=Southern|first2=L. M.|last3=Deschner|first3=T.|last4=Pika|first4=S.|year=2022|title=Application of insects to wounds of self and others by chimpanzees in the wild|journal=Current Biology|volume=32|issue=3|pages=R112–R113|doi=10.1016/j.cub.2021.12.045|pmid=35134354|s2cid=246638843|doi-access=free|bibcode=2022CBio...32.R112M }}</ref> Chimpanzees also display signs of [[animal culture|culture]] among groups, with the learning and transmission of variations in grooming, tool use and foraging techniques leading to localized traditions.<ref>{{cite journal |first1=A.|last1=Whiten |first2=A. |last2=Spiteri |first3=V. |last3=Horner |first4=K. E. |last4=Bonnie |first5=S. P. |last5=Lambeth |first6=S. J. |last6=Schapiro |first7=F. B. M. |last7=de Waal |author7-link=Frans de Waal |title=Transmission of multiple traditions within and between chimpanzee groups |journal=Current Biology |volume=17 |issue=12 |date=2007 |pages=1038–1043 |doi=10.1016/j.cub.2007.05.031 |pmid=17555968 |s2cid=1236151|doi-access=free |bibcode=2007CBio...17.1038W }}</ref>

A 30-year study at [[Kyoto University]]'s [[Primate Research Institute]] has shown that chimpanzees are able to learn to recognise the numbers 1 to 9 and their values. The chimpanzees further show an aptitude for [[eidetic memory]], demonstrated in experiments in which the jumbled digits are flashed onto a computer screen for less than a quarter of a second. One chimpanzee, [[Ayumu (chimpanzee)|Ayumu]], was able to correctly and quickly point to the positions where they appeared in ascending order. Ayumu performed better than human adults who were given the same test.<ref name="symbol">{{cite journal |author=Matsuzawa, T. |year=2009 |title=Symbolic representation of number in chimpanzees |journal=Current Opinion in Neurobiology |volume=19 |issue=1 |pages=92–98 |doi=10.1016/j.conb.2009.04.007 |pmid=19447029 |s2cid=14799654}}</ref>

In controlled [[cooperative pulling paradigm|experiments on cooperation]], chimpanzees show a basic understanding of cooperation, and recruit the best collaborators.<ref name="recruit">{{cite journal |last1=Melis |first1=A. P. |first2=B. |last2=Hare |first3=M. |last3=Tomasello |s2cid=9219039 |title=Chimpanzees recruit the best collaborators |journal=Science |volume=311 |issue=5765 |year=2006 |pages=1297–1300 |bibcode=2006Sci...311.1297M |doi=10.1126/science.1123007 |pmid=16513985}}</ref> In a group setting with a device that delivered food rewards only to cooperating chimpanzees, cooperation first increased, then, due to competitive behaviour, decreased, before finally increasing to the highest level through punishment and other arbitrage behaviours.<ref name="Suchak">{{cite journal |last1=Suchak |first1=M. |first2=T. M. |last2=Eppley |first3=M. W. |last3=Campbell |first4=R. A. |last4=Feldman |first5=L. F. |last5=Quarles |first6=F. B. M. |last6=de Waal |author6-link=Frans de Waal |title=How chimpanzees cooperate in a competitive world |journal=Proceedings of the National Academy of Sciences |year=2016 |volume=113 |issue=36 |pages=10215–10220 |doi=10.1073/pnas.1611826113 |pmid=27551075 |pmc=5018789 |bibcode=2016PNAS..11310215S |doi-access=free}}</ref>

Great apes show [[Laughter in animals|laughter-like vocalisations]] in response to physical contact, such as wrestling, play chasing, or [[tickling]]. This is documented in wild and captive chimpanzees. Chimpanzee laughter is not readily recognisable to humans as such, because it is generated by alternating inhalations and exhalations that sound more like breathing and panting. Instances in which nonhuman primates have expressed joy have been reported. Humans and chimpanzees share similar ticklish areas of the body, such as the armpits and belly. The enjoyment of tickling in chimpanzees does not diminish with age.<ref name="Discover2003">{{Cite web |author=Johnson, S. |date=1 April 2003 |title=Emotions and the brain |url=http://discovermagazine.com/2003/apr/featlaugh |url-status=dead |publisher=Discover Magazine |access-date=11 March 2019 |archive-date=19 July 2011 |archive-url=https://web.archive.org/web/20110719034137/http://discovermagazine.com/2003/apr/featlaugh }}</ref>

Chimpanzees have displayed different behaviours in response to a dying or dead group member. When witnessing a sudden death, the other group members act in frenzy, with vocalisations, aggressive displays, and touching of the corpse. In one case chimpanzees cared for a dying elder, then attended and cleaned the corpse. Afterward, they avoided the spot where the elder died and behaved in a more subdued manner.<ref>{{cite journal |author1=Anderson, J. R. |author2=Gillies, A. |author3=Lock, L. C. |year=2010 |title=''Pan'' thanatology |journal=Current Biology |volume=20 |issue=8 |pages=R349–R351 |doi=10.1016/j.cub.2010.02.010 |pmid=21749950|s2cid=21208590|doi-access=free |bibcode=2010CBio...20.R349A }}</ref> Mothers have been reported to carry around and groom their dead infants for several days.<ref>{{cite journal |author1=Dora, B. |author2=Humle, T. |author3=Koops, K. |author4=Sousa, C. |author5=Hayashi, M. |author6=Matsuzawa, T. |year=2010 |title=Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants |journal=Current Biology |volume=20 |issue=8 |pages=R351–R352 |doi=10.1016/j.cub.2010.02.031 |pmid=21749951|s2cid=52333419|doi-access=free |bibcode=2010CBio...20.R351B }}</ref>

Experimenters now and then witness behaviour that cannot be readily reconciled with chimpanzee intelligence or [[theory of mind]]. [[Wolfgang Köhler]], for instance, reported insightful behaviour in chimpanzees, but he likewise often observed that they experienced "special difficulty" in solving simple problems.<ref>{{Cite book |last=Köhler |first=Wolfgang |author-link=Wolfgang Köhler |year=1925 |title=The mentality of apes |edition=1st |others=translated from the 2nd German edition by Ella Winter |location=London |publisher=Kegan Paul Trench Trubner & Co. |page=65 |url=https://archive.org/details/in.ernet.dli.2015.187610/page/n69/mode/2up?q=special+difficulty}} See also Wiki page [[The Mentality of Apes]].</ref> Researchers also reported that, when faced with a choice between two persons, chimpanzees were just as likely to beg food from a person who could see the begging gesture as from a person who could not, thereby raising the possibility that chimpanzees lack [[theory of mind]].<ref>{{Cite journal |last1=Povinelli |first1=D. J. |last2=Eddy |first2=T. J. |year=1996 |title=What young chimpanzees know about seeing |journal=Monographs of the Society for Research in Child Development |volume=61 |issue=3 |pages=1–189|doi=10.2307/1166159 |jstor=1166159}}</ref>

===Tool use===
{{further |Tool use by animals}}
[[File:Cultural-differences-in-ant-dipping-tool-length-between-neighbouring-chimpanzee-communities-at-srep12456-s2.ogv|thumb|right |Chimpanzees using twigs to dip for ants]]
Nearly all chimpanzee populations have been recorded using tools. They modify sticks, rocks, grass, and leaves and use them when foraging for termites and ants,<ref name=":1">{{Cite journal |last1=Humle |first1=T. |last2=Matsuzawa |first2=T. |date=2001 |title=Behavioural diversity among the wild chimpanzee populations of Bossou and neighbouring areas, Guinea and Côte d'Ivoire, West Africa |journal=Folia Primatologica |volume=72 |issue=2 |pages=57–68 |doi=10.1159/000049924 |pmid=11490130 |s2cid=19827175 |issn=0015-5713}}</ref> nuts,<ref name=":1"/><ref>{{Cite journal |last=Ohashi |first=G. |date=2015 |title=Pestle-pounding and nut-cracking by wild chimpanzees at Kpala, Liberia |journal=Primates |volume=56 |issue=2 |pages=113–117 |doi=10.1007/s10329-015-0459-1 |pmid=25721009 |s2cid=18857210 |issn=0032-8332}}</ref><ref>{{Cite journal |last1=Hannah |first1=A. C. |last2=McGrew |first2=W. C. |date=1987 |title=Chimpanzees using stones to crack open oil palm nuts in Liberia |journal=Primates |volume=28 |issue=1 |pages=31–46 |doi=10.1007/BF02382181 |s2cid=24738945 |issn=1610-7365}}</ref><ref>{{Cite journal |last1=Marshall-Pescini |first1=S. |last2=Whiten |first2=A. |date=2008 |title=Chimpanzees (''Pan troglodytes'') and the question of cumulative culture: an experimental approach |journal=Animal Cognition |volume=11 |issue=3 |pages=449–456 |doi=10.1007/s10071-007-0135-y |pmid=18204869 |s2cid=25295372 |issn=1435-9448}}</ref> honey,<ref>{{Cite journal |last1=Boesch |first1=C. |last2=Head |first2=J. |last3=Robbins |first3=M. M. |date=June 2009 |title=Complex tool sets for honey extraction among chimpanzees in Loango National Park, Gabon |journal=Journal of Human Evolution |volume=56 |issue=6 |pages=560–569 |doi=10.1016/j.jhevol.2009.04.001 |pmid=19457542 |bibcode=2009JHumE..56..560B |issn=0047-2484}}</ref> algae<ref>{{Cite journal |last1=Boesch |first1=C. |last2=Kalan |first2=A. K. |last3=Agbor |first3=A. |last4=Arandjelovic |first4=M. |last5=Dieguez |first5=P. |last6=Lapeyre |first6=V. |last7=Kühl |first7=H. S. |date=2016 |title=Chimpanzees routinely fish for algae with tools during the dry season in Bakoun, Guinea |journal=American Journal of Primatology |volume=79 |issue=3 |pages=e22613 |doi=10.1002/ajp.22613 |pmid=27813136 |s2cid=24832972 |issn=0275-2565}}</ref> or water. Despite the lack of complexity, forethought and skill are apparent in making these tools.<ref name="Boesch1993">{{cite book |author=Boesch, C. |author2=Boesch, H. |date=1993 |chapter=Diversity of tool use and tool-making in wild chimpanzees |pages=158–87 |editor=Berthelet, A. |editor2=Chavaillon, J. |title=The Use of Tools by Human and Non-human Primates |location=Oxford, UK |publisher=Oxford University Press |isbn=978-0-19-852263-8}}</ref> Chimpanzees have used stone tools since at least 4,300 years ago.<ref>{{cite journal |author=Mercader. J. |display-authors=etal |title=4,300-year-old chimpanzee sites and the origins of percussive stone technology |journal=PNAS |volume=104 |issue=9 |pages=3043–8 |date=February 2007 |pmid=17360606 |pmc=1805589 |doi=10.1073/pnas.0607909104 |bibcode=2007PNAS..104.3043M |doi-access=free}}</ref>

A chimpanzee from the [[Kasakela chimpanzee community]] was the first nonhuman animal reported making a tool, by modifying a twig to use as an instrument for extracting termites from their mound.<ref name="Goodall 1971">{{cite book |title=In the Shadow of Man |author=Goodall, J. |author-link=Jane Goodall |pages=[https://archive.org/details/inshadowofman300good/page/35 35–37] |year=1971 |publisher=Houghton Mifflin |isbn=978-0-395-33145-3 |url=https://archive.org/details/inshadowofman300good/page/35}}</ref><ref>{{cite web |title=Gombe timeline |url=http://www.janegoodall.org/jane/study-corner/chimpanzees/gombe-timeline.asp |archive-url=https://web.archive.org/web/20080125194313/http://www.janegoodall.org/jane/study-corner/chimpanzees/gombe-timeline.asp |archive-date=25 January 2008 |publisher=[[Jane Goodall Institute]] |access-date=5 March 2009}}</ref> At Taï, chimpanzees simply use their hands to extract termites.<ref name="Boesch1993"/> When foraging for honey, chimpanzees use modified short sticks to scoop the honey out of the hive if the bees are [[Stingless bees|stingless]]. For hives of the dangerous [[African honeybee]]s, chimpanzees use longer and thinner sticks to extract the honey.<ref>{{cite journal |author=Stanford, C. B. |display-authors=etal |title=Chimpanzees in Bwindi-Impenetrable National Park, Uganda, use different tools to obtain different types of honey |journal=Primates; Journal of Primatology |volume=41 |issue=3 |pages=337–341 |date=July 2000 |pmid=30545184 |doi=10.1007/BF02557602 |s2cid=23000084}}</ref>

Chimpanzees also fish for ants using the same tactic.<ref name="Boesch Boesch 1982"/> Ant dipping is difficult and some chimpanzees never master it. West African chimpanzees crack open hard nuts with stones or branches.<ref name="Boesch1993"/><ref name="Boesch Boesch 1982">{{cite journal |last1=Boesch |first1=C. |last2=Boesch |first2=H. |s2cid=85037244 |title=Optimisation of nut-cracking with natural hammers by wild chimpanzees |journal=Behaviour |date=1982 |volume=83 |issue=3/4 |pages=265–286 |jstor=4534230 |doi=10.1163/156853983x00192}}</ref> Some forethought in this activity is apparent, as these tools are not found together or where the nuts are collected. Nut cracking is also difficult and must be learned.<ref name="Boesch Boesch 1982"/> Chimpanzees also use leaves as sponges or spoons to drink water.<ref>{{cite journal |author=Sugiyama, Y. |year=1995 |title=Drinking tools of wild chimpanzees at Bossou |journal=American Journal of Primatology |volume=37 |issue=1 |pages=263–269 |doi=10.1002/ajp.1350370308 |pmid=31936951 |s2cid=86473603}}</ref>

West African chimpanzees in Senegal were found to sharpen sticks with their teeth, which were then used to spear [[Senegal bushbaby|Senegal bushbabies]] out of small holes in trees.<ref>{{cite web |url=http://news.discovery.com/animals/female-chimps-seen-making-wielding-spears-150414.htm |title=Female chimps seen making, wielding spears |last1=Viegas |first1=J. |date=14 April 2015 |publisher=Discovery |access-date=15 April 2015 |archive-date=15 April 2015 |archive-url=https://web.archive.org/web/20150415123148/http://news.discovery.com/animals/female-chimps-seen-making-wielding-spears-150414.htm |url-status=dead}}</ref> An eastern chimpanzee has been observed using a modified branch as a tool to capture a [[squirrel]].<ref>{{cite journal |author=Huffman, M. A. |author2=Kalunde, M. S. |title=Tool-assisted predation on a squirrel by a female chimpanzee in the Mahale Mountains, Tanzania |journal=Primates |date=January 1993 |volume=34 |issue=1 |pages=93–98 |doi=10.1007/BF02381285 |s2cid=28006860}}</ref> Chimpanzees living in Tanzania were found to deliberately choose plants that provide materials that produce more flexible tools for termite fishing.<ref>{{Cite journal |last1=Pascual-Garrido |first1=Alejandra |last2=Carvalho |first2=Susana |last3=Mjungu |first3=Deus |last4=Schulz-Kornas |first4=Ellen |last5=Casteren |first5=Adam van |date=2025-03-24 |title=Engineering skills in the manufacture of tools by wild chimpanzees |url=https://www.cell.com/iscience/fulltext/S2589-0042(25)00419-5?_returnURL=https://linkinghub.elsevier.com/retrieve/pii/S2589004225004195?showall=true |journal=iScience |language=English |volume= |issue= |doi=10.1016/j.isci.2025.112158 |issn=2589-0042|doi-access=free }}</ref>

Whilst experimental studies on captive chimpanzees have found that many of their species-typical tool-use behaviours can be individually learnt by each chimpanzees,<ref>{{cite journal |last1=Bandini |first1=E. |last2=Tennie |first2=C. |title=Exploring the role of individual learning in animal tool-use |journal=PeerJ |date=2020 |volume=8 |issue=e9877 |pages=e9877 |doi=10.7717/peerj.9877 |pmid=33033659 |pmc=7521350 |doi-access=free }}</ref> a 2021 study on their abilities to make and use stone flakes, in a similar way as hypothesised for early hominins, did not find this behaviour across two populations of chimpanzees—suggesting that this behaviour is outside the chimpanzee species-typical range.<ref>{{cite journal |last1=Bandini |first1=E. |last2=Motes-Rodrigo |first2=A. |last3=Archer |first3=W. |last4=Minchin |first4=T. |last5=Axelsen |first5=H. |last6=Hernandez-Aguilar |first6=R. A. |last7=McPherron |first7=S. |last8=Tennie |first8=C. |title=Naïve, unenculturated chimpanzees fail to make and use flaked stone tools |journal=Open Research Europe |date=2021 |volume=1 |issue=20 |page=20 |doi=10.12688/openreseurope.13186.2|pmid=35253007 |pmc=7612464 |s2cid=237868827 |doi-access=free }}</ref>

===Language===
{{Main |Great ape language}}
[[File:HugoRheinholdApeWithSkull.DarwinMonkey.2.jpg|thumb|upright|right|[[Hugo Rheinhold]]'s ''[[Affe mit Schädel]]'' ("Ape with skull"), {{Circa|1893}}]]
Scientists have attempted to teach human [[language]] to several species of great ape. One early attempt by Allen and Beatrix Gardner in the 1960s involved spending 51 months teaching [[American Sign Language]] to a chimpanzee named [[Washoe (chimpanzee)|Washoe]]. The Gardners reported that Washoe learned 151 signs, and had spontaneously taught them to other chimpanzees, including her adopted son, [[Loulis]].<ref>{{Cite journal |author1=Gardner, R. A. |author2=Gardner, B. T. |year=1969 |title=Teaching sign language to a chimpanzee |journal=Science |volume=165 |pages=664–672 |doi=10.1126/science.165.3894.664 |pmid=5793972 |issue=3894 |bibcode=1969Sci...165..664G |citeseerx=10.1.1.384.4164}}</ref> Over a longer period of time, Washoe was reported to have learned over 350 signs.<ref>{{Cite book |author1=Allen, G. R. |author2=Gardner, B. T. |year=1980 |chapter=Comparative psychology and language acquisition |editor-first1=T. A. |editor-last1=Sebok |editor-first2=J. |editor-last2=Umiker-Sebok |title=Speaking of Apes: A Critical Anthology of Two-Way Communication with Man |location=New York |publisher=Plenum Press |pages=287–329 |isbn=978-0-306-40279-1}}</ref>

Debate is ongoing among scientists such as [[David Premack]] about chimpanzees' ability to learn language. Since the early reports on Washoe, numerous other studies have been conducted, with varying levels of success.<ref name="GAT">{{cite web |url=http://www.greatapetrust.org/bonobo/language/ |title=Language of bonobos |publisher=Great Ape Trust |archive-url=https://web.archive.org/web/20040815161414/http://www.greatapetrust.org/bonobo/language/ |archive-date=15 August 2004 |access-date=16 January 2012}}</ref> One involved a chimpanzee jokingly named [[Nim Chimpsky]] (in allusion to the theorist of language [[Noam Chomsky]]), trained by Herbert Terrace of [[Columbia University]]. Although his initial reports were quite positive, in November 1979, Terrace and his team, including psycholinguist [[Thomas Bever]], re-evaluated the videotapes of Nim with his trainers, analyzing them frame by frame for signs, as well as for exact context (what was happening both before and after Nim's signs). In the reanalysis, Terrace and Bever concluded that Nim's utterances could be explained merely as prompting on the part of the experimenters, as well as mistakes in reporting the data. "Much of the apes' behaviour is pure drill", he said. "Language still stands as an important definition of the human species." In this reversal, Terrace now argued Nim's use of ASL was not like human [[language acquisition]]. Nim never initiated conversations himself, rarely introduced new words, and mostly imitated what the humans did. More importantly, Nim's word strings varied in their ordering, suggesting that he was incapable of [[syntax]]. Nim's sentences also did not grow in length, unlike human children whose vocabulary and sentence length show a strong positive correlation.<ref name="Wynne 2007">{{cite web |author-link1=Clive Wynne |last=Wynne |first=C. |url=http://www.skeptic.com/eskeptic/07-10-31 |title=Aping language |work=eSkeptic |publisher=Skeptic |date=31 October 2007 |access-date=28 January 2011 |archive-date=16 April 2011 |archive-url=https://web.archive.org/web/20110416095851/http://www.skeptic.com/eskeptic/07-10-31/ |url-status=live }}</ref>