Editing Corvidae (section)

===Intelligence===
{{See also|Bird intelligence}}
{{Split section|Corvid intelligence|date=July 2023}}
Jerison (1973) has suggested that the degree of brain [[encephalization]] (the ratio of brain size to body size, EQ) may correlate with an [[animal intelligence|animal's intelligence]] and [[cognitive skills]].<ref>{{Citation|last=Jerison|first=Harry J.|title=Evolution of the Brain in Birds|date=1973|url=https://linkinghub.elsevier.com/retrieve/pii/B9780123852502500183|work=Evolution of the Brain and Intelligence|pages=177–199|publisher=Elsevier|doi=10.1016/b978-0-12-385250-2.50018-3|isbn=978-0-12-385250-2|access-date=11 March 2021}}</ref> Corvids and [[Psittacidae|psittacid]]s have higher EQ than other bird families, similar to that of the apes. Among the Corvidae, ravens possess the largest brain to body size ratio.<ref>{{Citation|last1=Emery|first1=Nathan J.|title=Comparing the Complex Cognition of Birds and Primates|date=2004|url=http://link.springer.com/10.1007/978-1-4419-8913-0_1|work=Comparative Vertebrate Cognition|pages=3–55|editor-last=Rogers|editor-first=Lesley J.|place=Boston, MA|publisher=Springer US|doi=10.1007/978-1-4419-8913-0_1|isbn=978-1-4613-4717-0|access-date=11 March 2021|last2=Clayton|first2=Nicola S.|editor2-last=Kaplan|editor2-first=Gisela}}</ref> In addition to the high EQ, the Corvid's intelligence is boosted by their living environment. Firstly, Corvids are found in some of the harshest environments on Earth, where surviving requires higher intelligence and better adaptations. Secondly, most of the Corvids are omnivorous, suggesting that they are exposed to a wider variety of different stimuli and environments. Furthermore, many corvid species live in a large family group, and demonstrate high social complexities.<ref>{{Cite journal|last=Emery|first=Nathan J|date=29 January 2006|title=Cognitive ornithology: the evolution of avian intelligence|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=361|issue=1465|pages=23–43|doi=10.1098/rstb.2005.1736|issn=0962-8436|pmc=1626540|pmid=16553307}}</ref>

Their intelligence is boosted by the long growing period of the young.<ref>{{cite news|title=Long childhoods and extended parenting help young crows grow smarter |url=https://phys.org/news/2020-06-childhoods-parenting-young-crows-smarter.html |access-date=2 July 2020 |work=phys.org}}</ref><ref>{{cite journal|last1=Heidt |first1=Amanda |title=Like humans, these big-brained birds may owe their smarts to long childhoods |journal=Science |date=8 June 2020 |doi=10.1126/science.abd2209|s2cid=225766325 }}</ref><ref>{{cite journal |last1=Uomini |first1=Natalie |last2=Fairlie |first2=Joanna |last3=Gray |first3=Russell D. |last4=Griesser |first4=Michael |title=Extended parenting and the evolution of cognition |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=20 July 2020 |volume=375 |issue=1803 |pages=20190495 |doi=10.1098/rstb.2019.0495 |pmid=32475334 |pmc=7293161 |doi-access=free }}</ref> By remaining with the parents, the young have more opportunities to learn necessary skills.

When compared to dogs and cats in an experiment testing the ability to seek out food according to three-dimensional clues, corvids out-performed the mammals.<ref name=Krushinskii/> A [[meta-analysis]] testing how often birds invented new ways to acquire food in the wild found corvids to be the most innovative birds.<ref>Rincon, Paul (22 February 2005) [http://news.bbc.co.uk/1/hi/sci/tech/4286965.stm Crows and jays top bird IQ scale]. BBC.</ref> A 2004 review suggested that their cognitive abilities are on par with those of non-human [[great apes]].<ref name=Emery/> Despite structural differences, the brains of corvids and great apes both evolved the ability to make geometrical measurements.

==== Empathy-consolation ====
Ravens are found to show bystander affiliation, and solicited bystander affiliation after aggressive conflicts.<ref>{{Cite journal|last1=Fraser|first1=Orlaith N.|last2=Bugnyar|first2=Thomas|date=12 May 2010|editor-last=Brosnan|editor-first=Sarah Frances|title=Do Ravens Show Consolation? Responses to Distressed Others|journal=PLOS ONE|volume=5|issue=5|pages=e10605|doi=10.1371/journal.pone.0010605|issn=1932-6203|pmc=2868892|pmid=20485685|bibcode=2010PLoSO...510605F|doi-access=free}}</ref> Most of the time, bystanders already sharing a valuable relationship with the victim are more likely to affiliate with the victim to alleviate the victim's distress ("consolation") as a representation of [[empathy]]. Ravens are believed to be able to be sensitive to other's emotions.

==== Empathy-emotional contagion ====
[[Emotion]] contagion refers to the [[emotional state]] matching between individuals. Adriaense et al. (2018) used a [[cognitive bias|bias]] paradigm to quantify [[emotional valence]], which along with [[emotional arousal]], define emotions.<ref>{{Cite journal|last1=Edgar|first1=Joanne L.|last2=Nicol|first2=Christine J.|date=December 2018|title=Socially-mediated arousal and contagion within domestic chick broods|journal=Scientific Reports|volume=8|issue=1|pages=10509|doi=10.1038/s41598-018-28923-8|issn=2045-2322|pmc=6043517|pmid=30002482|bibcode=2018NatSR...810509E}}</ref> They manipulated the positive and negative affective states in the demonstrator ravens, which showed significantly different responses to the two states: behaving pessimism to the negative states, and optimism to the positive states. Then, the researchers trained another observer raven to first observe the demonstrator's responses. The observer raven was then presented with ambiguous stimuli. The experiment results confirmed the existence of negative emotional contagions in ravens, while the positive emotional contagion remained unclear. Therefore, ravens are capable of both discerning the negative emotions in their conspecifics and showing signs of empathy.<ref>{{Cite journal|last1=Adriaense|first1=Jessie E. C.|last2=Martin|first2=Jordan S.|last3=Schiestl|first3=Martina|last4=Lamm|first4=Claus|last5=Bugnyar|first5=Thomas|date=4 June 2019|title=Negative emotional contagion and cognitive bias in common ravens (''Corvus corax'')|journal=Proceedings of the National Academy of Sciences|volume=116|issue=23|pages=11547–11552|doi=10.1073/pnas.1817066116|issn=0027-8424|pmc=6561263|pmid=31110007|bibcode=2019PNAS..11611547A |doi-access=free}}</ref>

==== Interspecific communications ====
[[Interspecific communication]]s are evolutionarily beneficial for species living in the same environment. Facial expressions are the most widely used method to express emotions by humans. Tate et al. (2006) explored the issue of non-human mammals processing the visual cues from faces to achieve interspecific communication with humans.<ref>{{Cite journal|last1=Tate|first1=Andrew J|last2=Fischer|first2=Hanno|last3=Leigh|first3=Andrea E|last4=Kendrick|first4=Keith M|date=29 December 2006|title=Behavioural and neurophysiological evidence for face identity and face emotion processing in animals|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=361|issue=1476|pages=2155–2172|doi=10.1098/rstb.2006.1937|issn=0962-8436|pmc=1764842|pmid=17118930}}</ref> Researchers also examined the avian species' capabilities to interpret this non-verbal communication, and their extent of sensitivity to human emotions. Based on the experimental subject of American Crows' behavioral changes to varying human gazes and facial expressions, Clucas et al. (2013) identified that crows are able to change their behaviors to the presence of direct human gaze, but did not respond differentially to human emotional facial expressions. They further suggested that the high intelligence of the crows enables them to adapt well to human-dominated environments.<ref>{{Cite journal|last1=Clucas|first1=Barbara|last2=Marzluff|first2=John M.|last3=Mackovjak|first3=David|last4=Palmquist|first4=Ila|date=April 2013|editor-last=Ebensperger|editor-first=L.|title=Do American Crows Pay Attention to Human Gaze and Facial Expressions?|url=http://doi.wiley.com/10.1111/eth.12064|journal=Ethology|volume=119|issue=4|pages=296–302|doi=10.1111/eth.12064|bibcode=2013Ethol.119..296C }}</ref>

==== Personality conformity ====
It is considered difficult to study emotions in animals when humans could not communicate with them. One way to identify animal [[personality]] traits is to observe the consistency of the individual's behavior over time and circumstances.<ref>{{Cite journal|last1=Both|first1=Christiaan|last2=Dingemanse|first2=Niels J.|last3=Drent|first3=Piet J.|last4=Tinbergen|first4=Joost M.|date=July 2005|title=Pairs of extreme avian personalities have highest reproductive success|journal=Journal of Animal Ecology|volume=74|issue=4|pages=667–674|doi=10.1111/j.1365-2656.2005.00962.x|issn=0021-8790|doi-access=free|bibcode=2005JAnEc..74..667B }}</ref><ref>{{Cite journal|last=Gosling|first=Samuel D.|date=2001|title=From mice to men: What can we learn about personality from animal research?|url=http://doi.apa.org/getdoi.cfm?doi=10.1037/0033-2909.127.1.45|journal=Psychological Bulletin|volume=127|issue=1|pages=45–86|doi=10.1037/0033-2909.127.1.45|pmid=11271756|issn=1939-1455}}</ref> For group-living species, there are two opposing hypotheses regarding the assortment of personalities within a group: the social niche specialization hypothesis, and the conformity hypothesis. To test these two hypotheses, McCune et al. (2018) performed an experiment on the boldness of two species in Corvidae: the [[Mexican Jay]] and [[California Scrub-Jay]]. Their results confirmed the conformity hypothesis, supported by the significant differences in the group effects.<ref>{{Cite journal|last1=Bergmüller|first1=Ralph|last2=Taborsky|first2=Michael|date=September 2010|title=Animal personality due to social niche specialisation|url=https://linkinghub.elsevier.com/retrieve/pii/S0169534710001515|journal=Trends in Ecology & Evolution|volume=25|issue=9|pages=504–511|doi=10.1016/j.tree.2010.06.012|pmid=20638151|bibcode=2010TEcoE..25..504B }}</ref>

==== Social construction ====
The individual personality is both determined by genetics and shaped by [[social context]]s.<ref>{{Cite book|last=Judith|first=University of Helsinki, Department of Finnish, Finno-Ugrian and Scandinavian Studies Koski, Sonja Burkart|url=http://worldcat.org/oclc/951545397|title=Common marmosets show social plasticity and group-level similarity in personality|date=6 March 2015|publisher=Nature Publishing Group|oclc=951545397}}</ref> Miller et al. (2016) examined the role of the developmental and social environment in personality formation in common ravens and carrion crows, which are highly social corvids. The researchers highlighted the correlation between social contexts and an individual's consistent behavior over time (personality), by showing that conspecific presence promoted the behavioral similarities between individuals. Therefore, the researchers demonstrated that social contexts had a significant impact on the development of the raven's and crow's personalities.<ref>{{Cite journal|last1=Miller|first1=Rachael|last2=Laskowski|first2=Kate L.|last3=Schiestl|first3=Martina|last4=Bugnyar|first4=Thomas|last5=Schwab|first5=Christine|date=5 February 2016|editor-last=Hemelrijk|editor-first=Charlotte K|title=Socially Driven Consistent Behavioural Differences during Development in Common Ravens and Carrion Crows|journal=PLOS ONE|volume=11|issue=2|pages=e0148822|doi=10.1371/journal.pone.0148822|issn=1932-6203|pmc=4746062|pmid=26848954|bibcode=2016PLoSO..1148822M|doi-access=free}}</ref>

==== Social complexity ====
The [[social complexity]] hypothesis suggests that living in a social group enhances the cognitive abilities of animals. Corvid ingenuity is represented through their feeding skills, [[memorization]] abilities, use of tools, and group behaviour. Living in large social groups has long been connected with high cognitive ability. To live in a large group, a member must be able to recognize individuals, and track the social position and foraging of other members over time. Members must also be able to distinguish between sex, age, reproductive status, and dominance, and to update this information constantly. It might be that social complexity corresponds to their high cognition, as well as contributing to the spread of information between members of the group.<ref name="Bond" />

==== Consciousness, culture-rudiments, and neurology ====
A study published in 2008 suggested that the [[Eurasian magpie]] is the only non-mammal species known to be able to recognize itself in a [[mirror test]],<ref name="prior2008">{{cite journal|last1=Prior|first1=Helmut|last2=Schwarz|first2=Ariane|last3=Güntürkün|first3=Onur|date=2008|editor1-last=De Waal|editor1-first=Frans|title=Mirror-Induced Behavior in the Magpie (''Pica pica''): Evidence of Self-Recognition|journal=PLOS Biology|volume=6|issue=8|pages=e202|doi=10.1371/journal.pbio.0060202|pmc=2517622|pmid=18715117 |doi-access=free }}</ref> but later research could not replicate this finding.<ref>{{Cite journal|last1=Soler|first1=M.|last2=Colmero|first2=J. M.|last3=Pérez-Contreras|first3=T.|last4=Peralta-Sánchez|first4=J. M.|title=Replication of the mirror mark test experiment in the magpie (Pica pica) does not provide evidence of self-recognition.|journal=Journal of Comparative Psychology|year=2020 |volume=134|issue=4 |pages=363–371|doi=10.1037/com0000223 |pmid=32406720 |s2cid=218636079 }}</ref> Studies using very similar setups could not find such behaviour in other corvids (e.g., Carrion crows<ref>{{Cite journal|last1=Brecht|first1=Katharina F.|last2=Müller|first2=Jan|last3=Nieder|first3=Andreas|date=November 2020|title=Carrion crows (Corvus corone corone) fail the mirror mark test yet again.|url=http://doi.apa.org/getdoi.cfm?doi=10.1037/com0000231|journal=Journal of Comparative Psychology|language=en|volume=134|issue=4|pages=372–378|doi=10.1037/com0000231|pmid=32463251 |s2cid=218976227 |issn=1939-2087}}</ref><ref>{{Cite journal|last1=Vanhooland|first1=Lisa-Claire|last2=Bugnyar|first2=Thomas|last3=Massen|first3=Jorg J. M.|date=May 2020|title=Crows (Corvus corone ssp.) check contingency in a mirror yet fail the mirror-mark test.|url=http://doi.apa.org/getdoi.cfm?doi=10.1037/com0000195|journal=Journal of Comparative Psychology|language=en|volume=134|issue=2|pages=158–169|doi=10.1037/com0000195|pmid=31589059 |s2cid=203850271 |issn=1939-2087}}</ref>). Magpies have been observed taking part in elaborate grieving rituals, which have been likened to human [[funeral]]s, including laying grass wreaths.<ref name="74.220.204.222">[http://74.220.204.222/Puplando/wp-content/uploads/2013/12/EMOSPA47.pdf Animal emotions, wild justice and why they matter: Grieving magpies, a pissy baboon, and empathic elephants] {{Webarchive|url=https://web.archive.org/web/20150610202118/http://74.220.204.222/Puplando/wp-content/uploads/2013/12/EMOSPA47.pdf |date=10 June 2015 }} Emotion, Space and Society xxx (2009) 1–4, Marc Bekoff</ref> Marc Bekoff, at the [[University of Colorado]], argues that it shows that they are capable of feeling complex emotions, including [[grief]].<ref name="74.220.204.222"/> Furthermore, [[carrion crow]]s show a neuronal response that correlates with their [[perception]] of a stimulus, which some scientists have argued to be an empirical marker of ([[Animal consciousness#Corvids|avian/corvid]]) [[Primary consciousness|sensory consciousness]]—the conscious perception of sensory input—in the crows which do not have a [[cerebral cortex]].<ref>{{cite news |title=Researchers show conscious processes in birds' brains for the first time |url=https://phys.org/news/2020-09-conscious-birds-brains.html |access-date=9 October 2020 |work=phys.org}}</ref><ref>{{cite journal |last1=Nieder |first1=Andreas |last2=Wagener |first2=Lysann |last3=Rinnert |first3=Paul |title=A neural correlate of sensory consciousness in a corvid bird |journal=Science |date=25 September 2020 |volume=369 |issue=6511 |pages=1626–1629 |doi=10.1126/science.abb1447 |pmid=32973028 |bibcode=2020Sci...369.1626N |s2cid=221881862 |url=https://www.science.org/doi/10.1126/science.abb1447 |access-date=9 October 2020 |issn=0036-8075}}</ref> A related study shows that the [[Avian pallium|birds' pallium's]] neuroarchitecture is reminiscent of the mammalian cortex.<ref>{{cite news |last1=Stetka |first1=Bret |title=Bird Brains Are Far More Humanlike Than Once Thought |url=https://www.scientificamerican.com/article/bird-brains-are-far-more-humanlike-than-once-thought/ |access-date=23 October 2020 |work=Scientific American}}</ref><ref>{{cite journal |last1=Stacho |first1=Martin |last2=Herold |first2=Christina |last3=Rook |first3=Noemi |last4=Wagner |first4=Hermann |last5=Axer |first5=Markus |last6=Amunts |first6=Katrin |last7=Güntürkün |first7=Onur |title=A cortex-like canonical circuit in the avian forebrain |journal=Science |date=25 September 2020 |volume=369 |issue=6511 |pages=eabc5534 |doi=10.1126/science.abc5534 |pmid=32973004 |s2cid=221882087 |url=https://www.science.org/doi/10.1126/science.abc5534 |access-date=16 October 2020 |issn=0036-8075}}</ref>

====Tool use, memory, and complex rational thought====
{{See also|Tool use by animals#Corvids}}
[[File:Cognitive-Processes-Associated-with-Sequential-Tool-Use-in-New-Caledonian-Crows-pone.0006471.s002.ogv|thumb|350px|A [[New Caledonian crow]] uses a tool to retrieve the correct tool to obtain food.]]
There are also specific examples of corvid cleverness. One [[carrion crow]] was documented cracking nuts by placing them on a crosswalk, letting the passing cars crack the shell, waiting for the light to turn red, and then safely retrieving the contents.<ref>{{cite web|url=https://www.youtube.com/watch?v=BGPGknpq3e0 | archive-url=https://ghostarchive.org/varchive/youtube/20211107/BGPGknpq3e0| archive-date=7 November 2021 | url-status=live|title=Attenborough – Crows in the City |publisher=YouTube.com |date=12 February 2007 |access-date=9 March 2013}}{{cbignore}}</ref> A group of crows in England took turns lifting garbage bin lids while their companions collected food.{{citation needed|date=February 2025}}

Members of the corvid family have been known to watch other birds, remember where they hide their food, then return once the owner leaves.<ref>{{cite journal|author1=Burnell, Kristi L. |author2=Tomback, Diane F. |author2-link=Diana Tomback|year=1985|jstor=4086793 |title=Steller's jays steal Grey Jay caches: field and laboratory observation|journal=Auk|volume= 102|issue=2|pages=417–419|doi=10.2307/4086793|url=http://sora.unm.edu/node/24119}}</ref><ref>{{cite journal|author=Waite, Thomas A. |year=1992|jstor=1369297 |title=Social hoarding and a load size-distance relationship in Gray Jays|journal=The Condor|url=http://sora.unm.edu/node/104654|volume=94|issue=4|pages=995–998|doi=10.2307/1369297|s2cid=86971311 }}</ref> Corvids also move their food around between hiding places to avoid thievery—but only if they have previously been thieves themselves (that is, they remember previous relevant social contexts, use their own experience of having been a thief to predict the behavior of a pilferer, and can determine the safest course to protect their caches from being pilfered). Studies to assess similar cognitive abilities in apes have been inconclusive.<ref>Owen, James (9 December 2004) [https://web.archive.org/web/20041212040209/http://news.nationalgeographic.com/news/2004/12/1209_041209_crows_apes.html Crows as Clever as Great Apes, Study Says]. ''[[National Geographic News]]'', Retrieved 2007-NOV-10.</ref>

The ability to hide food requires highly accurate [[spatial memories]]. Corvids have been recorded to recall their food's hiding places up to nine months later. It is suggested that vertical landmarks (like trees) are used to remember locations. There has also been evidence that [[California scrub jay]]s, which store perishable foods, not only remember where they stored their food, but for how long. This has been compared to [[episodic memory]], previously thought unique to humans.<ref name = claytonemery2005 />

[[New Caledonian crow]]s (''Corvus moneduloides'') are notable for their highly developed tool fabrication. They make angling tools of twigs and leaves trimmed into hooks, and then subsequently use the hooks to pull insect larvae from tree holes. Tools are engineered according to task, and apparently, also to learned preferences. Recent studies revealed abilities to solve complicated problems, which suggested high levels of innovation of a complex nature.<ref>{{cite news|last=Morelle |first=Rebecca |author-link=Rebecca Morelle |url=http://news.bbc.co.uk/2/hi/science/nature/8631486.stm |title=BBC On-line: Clever New Caledonian crows can use three tools |work=BBC News |date=20 April 2010 |access-date=9 March 2013}}</ref><ref>{{Cite web|last=Baraniuk|first=Chris|date=12 December 2020|title=Crows could be the smartest animal other than primates|url=https://www.bbc.com/future/article/20191211-crows-could-be-the-smartest-animal-other-than-primates|access-date=31 August 2020|website=BBC}}</ref> Other corvids that have been observed using tools include: the [[American crow]], [[blue jay]], and [[green jay]]. Researchers have discovered that [[New Caledonian crow]]s do not just use single objects as tools—they can also construct novel compound tools through assemblage of otherwise non-functional elements.<ref>{{Cite journal|last1=Bayern|first1=A. M. P. von|last2=Danel|first2=S.|last3=Auersperg|first3=A. M. I.|last4=Mioduszewska|first4=B.|last5=Kacelnik|first5=A.|date=24 October 2018|title=Compound tool construction by New Caledonian crows|journal=Scientific Reports|volume=8|issue=1|page=15676|doi=10.1038/s41598-018-33458-z|pmid=30356096|issn=2045-2322|doi-access=free|pmc=6200727|bibcode=2018NatSR...815676B}}</ref><ref>{{Cite web|url=https://www.sciencealert.com/crows-are-so-smart-they-can-make-compound-tools-out-of-multiple-parts|title=Crows Can Build Compound Tools Out of Multiple Parts, And Are You Even Surprised|last=Starr|first=Michelle|date=25 October 2018|website=ScienceAlert|access-date=4 April 2020}}</ref> Diversity in tool design among corvids suggests cultural variation. Again, great apes are the only other animals known to use tools in such a fashion.<ref name = claytonemery2005 />

[[Clark's nutcracker]]s and [[jackdaw]]s were compared in a 2002 study based on geometric rule learning. The corvids, along with a [[domestic pigeon]], had to locate a target between two landmarks, while distances and landmarks were altered. The nutcrackers were more accurate in their searches than the jackdaws and pigeons.<ref name=Jones/>

==== Implications and specific comparisons with other animals ====
[[File:Proportions of correct responses as a function of species.webp|thumb|Proportions of correct responses as a function of species (R: ravens; C: chimpanzees; O: orang-utans)<ref name="10.1038/s41598-020-77060-8"/>]]

The [[scarecrow]] is an archetypal scare tactic in the agricultural business. However, due to corvids' quick wit, scarecrows are soon ignored, and used as perches. Despite farmers' efforts to rid themselves of corvid pests, their attempts have only expanded corvid territories, and strengthened their numbers.<ref name = shadesfonight />

Contrary to earlier [[teleological]] classifications, in which they were seen as "highest" songbirds due to their intelligence, current [[systematics]] might place corvids—based on their total number of physical characteristics, instead of just their brains (which are the most developed of birds)—in the lower middle of the passerine evolutionary tree, dependent on which subgroup is chosen as the most derived.<ref name = j&f2006 /> As per one observer:

{{blockquote|During the 19th century, there arose the belief that these were the "most advanced" birds, based upon the belief that Darwinian evolution brings "progress." In such a classification, the "most intelligent" of birds were listed last, reflecting their position "atop the pyramid." Modern biologists reject the concept of hierarchical "progress" in evolution [...].<ref name = robertson2000 />}}

The other major group of highly intelligent birds of the order [[Psittaciformes]] (which includes [[Psittacidae|'true' parrots]], [[cockatoo]]s, and [[New Zealand parrot]]s) is not closely related to corvids.

A study found that four-month-old ravens can have physical and social cognitive skills similar to that of adult great apes, and concluded that the "dynamic of the different influences that, during [[ontogeny]], contributes to adult cognition" is required for the study of cognition.<ref>{{cite news |title=Cognitive performance of four-month-old ravens may parallel adult apes |url=https://phys.org/news/2020-12-cognitive-four-months-old-ravens-parallel-adult.html |access-date=17 January 2021 |work=phys.org}}</ref><ref name="10.1038/s41598-020-77060-8">{{cite journal |last1=Pika |first1=Simone |last2=Sima |first2=Miriam Jennifer |last3=Blum |first3=Christian R. |last4=Herrmann |first4=Esther |last5=Mundry |first5=Roger |title=Ravens parallel great apes in physical and social cognitive skills |journal=Scientific Reports |date=10 December 2020 |volume=10 |issue=1 |page=20617 |doi=10.1038/s41598-020-77060-8 |pmid=33303790 |pmc=7728792 |bibcode=2020NatSR..1020617P |issn=2045-2322}} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref>