Difference between revisions of "Timeline of non-human animal intelligence"

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| 1988 || || || "Wasserman says the pigeon experiment comes from a project published in 1988 and featured in the New York Times in which University of Iowa researchers discovered pigeons could distinguish among four categories of objects."<ref>{{cite web |last1=Agnew-Iowa |first1=Sara |title=Pigeons are smarter than you'd think |url=https://www.futurity.org/pigeons-intelligence-856552/ |website=Futurity |access-date=8 October 2022 |date=16 February 2015}}</ref>
 
| 1988 || || || "Wasserman says the pigeon experiment comes from a project published in 1988 and featured in the New York Times in which University of Iowa researchers discovered pigeons could distinguish among four categories of objects."<ref>{{cite web |last1=Agnew-Iowa |first1=Sara |title=Pigeons are smarter than you'd think |url=https://www.futurity.org/pigeons-intelligence-856552/ |website=Futurity |access-date=8 October 2022 |date=16 February 2015}}</ref>
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| 1990 || || || "Povinelli et al. (1990) points out that most evidence in support of great ape theory of mind involves naturalistic settings to which the apes have already adapted through past learning. Their "reinterpretation hypothesis" explains away evidence supporting attribution of mental states to others in chimpanzees as merely evidence of risk-based learning; that is, the chimpanzees learn through experience that certain behaviors in other chimpanzees have a probability of leading to certain responses, without necessarily attributing knowledge or other intentional states to those other chimpanzees. They have proposed testing theory of mind abilities in great apes in novel, and not naturalistic settings."<ref>{{cite journal |last1=Povinelli |first1=Daniel J. |last2=Nelson |first2=Kurt E. |last3=Boysen |first3=Sarah T. |title=Inferences about guessing and knowing by chimpanzees (Pan troglodytes). |journal=Journal of Comparative Psychology |date=1990 |volume=104 |issue=3 |pages=203–210 |doi=10.1037/0735-7036.104.3.203 |url=https://psycnet.apa.org/doiLanding?doi=10.1037%2F0735-7036.104.3.203 |language=en |issn=1939-2087}}</ref>
 
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| 1995 || {{w|Dolphin}} || || "Marten and Psarakos used television to test dolphin self-awareness.<ref>Marten, Ken and Psarakos, Suchi "Using Self-View Television to Distinguish between Self-Examination and Social Behavior in the Bottlenose Dolphin (''Tursiops truncatus'')" (''Consciousness and Cognition'', Volume 4, Number 2, June 1995)</ref> They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed the mirror test.<ref name="Mirror">{{Cite journal |last=Reiss |first=D |last2=Marino |first2=L |date=8 May 2001 |title=Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=98 |issue=10 |pages=5937–42|doi=10.1073/pnas.101086398 |pmc=33317 |pmid=11331768}}</ref> However, some researchers have argued that evidence for self-awareness has not been convincingly demonstrated."<ref>Gallup Jr, Gordon G., and James R. Anderson. "Self-recognition in animals: Where do we stand 50 years later? Lessons from cleaner wrasse and other species." Psychology of Consciousness: Theory, Research, and Practice (2019).</ref>
 
| 1995 || {{w|Dolphin}} || || "Marten and Psarakos used television to test dolphin self-awareness.<ref>Marten, Ken and Psarakos, Suchi "Using Self-View Television to Distinguish between Self-Examination and Social Behavior in the Bottlenose Dolphin (''Tursiops truncatus'')" (''Consciousness and Cognition'', Volume 4, Number 2, June 1995)</ref> They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed the mirror test.<ref name="Mirror">{{Cite journal |last=Reiss |first=D |last2=Marino |first2=L |date=8 May 2001 |title=Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=98 |issue=10 |pages=5937–42|doi=10.1073/pnas.101086398 |pmc=33317 |pmid=11331768}}</ref> However, some researchers have argued that evidence for self-awareness has not been convincingly demonstrated."<ref>Gallup Jr, Gordon G., and James R. Anderson. "Self-recognition in animals: Where do we stand 50 years later? Lessons from cleaner wrasse and other species." Psychology of Consciousness: Theory, Research, and Practice (2019).</ref>

Revision as of 16:45, 12 October 2022

This is a timeline of FIXME.

Sample questions

The following are some interesting questions that can be answered by reading this timeline:

Big picture

Time period Development summary More details
1950s Cognitive revolution
1950s–1960s "During the 1950s and 1960s, researchers started to suggest that large brains in primates were due to their complex social life."[1]

Full timeline

Year Species/taxonomy Event type Details
1858 General "The word anthropomorphism existed for a long time, mainly to describe gods and celestial beings as humanlike, but its likely first usage for animals was made in 1858."[2]
1871 Hominidae "Darwin (1871) later published The Descent of Man and Selection in Relation to Sex, which made the mind-blowing conclusion that millions of years ago, humans shared a common ancestor with the other great apes. By kicking humans off their pedestal and inserting them into the animal kingdom, Darwin boldly redefined the centuries-old relationship between humans and animals—and made a lot of people really mad in the process."[2]
1882 Literature "In his book Animal Intelligence, Romanes (1882) reported dozens of stories of complex cognitive behaviors in everything from scorpions to elephants." " Romanes’ publication of Animal Intelligence in 1882 marks one possible start of the field"[2]
1899 Cat "A 'puzzle box' devised by Thorndike (1899, 2017) to study learning behavior of cats. A hungry cat is placed in a box which can be opened if the cat pushes a latch. A food reward ('positive reinforcer') will be obtained by the cat if it figures out how to escape from the box. Thorndike discovered that after several trials, the time it takes the cat to escape from the box decreases."[3]
1908 American psychologist Margaret Floy Washburn publishes The Animal Mind, a collection of experimental data on topics like sensory systems, learning, tool use, motivation, and subjective experience.[2]
1953 "The full concept of the Social Intelligence Hypothesis were first proposed by Michael Chance and Allan Mead in 1953 (Chance and Mead 1953), as they linked social complexity and enlargement of the neocortex in primates."[1]
1969 Literature Karen Pryor publishes The Creative Porpoise: Training for Novel Behavior.
1984 Dolphin (bottlenose) Scientists observe wild bottlenose dolphins in Shark Bay, Western Australia using a basic tool. When searching for food on the sea floor, many of these dolphins are seen tearing off pieces of sponge and wrapping them around their rostra, presumably to prevent abrasions and facilitate digging.[4]
1985 "Gordon Burghardt coined the term critical anthropomorphism for the use of data from multiple sources—including anthropomorphic ones—but which could then be formed into appropriately testable hypotheses (Burghardt, 1985)."[2]
1986 Dolphin "One hypothesis proposed by Jerison (1986) is that members of a pod of dolphins are able to share echolocation results with each other to create a better understanding of their surroundings."[5]
1988 "Wasserman says the pigeon experiment comes from a project published in 1988 and featured in the New York Times in which University of Iowa researchers discovered pigeons could distinguish among four categories of objects."[6]
1990 "Povinelli et al. (1990) points out that most evidence in support of great ape theory of mind involves naturalistic settings to which the apes have already adapted through past learning. Their "reinterpretation hypothesis" explains away evidence supporting attribution of mental states to others in chimpanzees as merely evidence of risk-based learning; that is, the chimpanzees learn through experience that certain behaviors in other chimpanzees have a probability of leading to certain responses, without necessarily attributing knowledge or other intentional states to those other chimpanzees. They have proposed testing theory of mind abilities in great apes in novel, and not naturalistic settings."[7]
1995 Dolphin "Marten and Psarakos used television to test dolphin self-awareness.[8] They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed the mirror test.[9] However, some researchers have argued that evidence for self-awareness has not been convincingly demonstrated."[10]
1995 "Nectarivorous birds such as hummingbirds also optimize their foraging by keeping track of the locations of good and bad flowers."[11]
2000 "Attitudinal reciprocity, which was shown in capuchin monkeys, Cebus apella (de Waal, 2000), describes a mechanism in which the choice to cooperate depends on the attitude the interaction partner has recently shown towards the subject (Brosnan and de Waal, 2002, de Waal, 2000)."[12]
2001 (January) "Animals have complex dreams, MIT researcher proves"[13]
2001 (January) Chimpanzee Hare et al. demonstrate that chimpanzees are aware of what other individuals know. They can also understand what another perceives, and they selectively choose food that is not visible to their competitor.[14]
2001 (November) "Asian elephants, Elephus maximus, have the greatest volume of cerebral cortex available for cognitive processing of all extant terrestrial animal species. A manifestation of cognitive behaviour is tool use and tool manufacture. Fly switching with branches is a type of tool use previously shown in captive Asian elephants to be effective in repelling flies and to vary in frequency with the intensity of flies."[15]
2002 "Brosnan and de Waal (2002) argued that many examples of animal altruism might depend on symmetry-based reciprocity."[16]
2007 (August 28) "Microscopic study of the human brain has revealed neural structures, enhanced wiring, and forms of connectivity among nerve cells not found in any animal, challenging the view that the human brain is simply an enlarged chimpanzee brain. On the other hand, cognitive studies have found animals to have abilities once thought unique to the human. This suggests a disparity between brain and mind."[17]
2009 Cat An experiment is conducted where cats can pull on a string to retrieve a treat under a plastic screen. When presented with one string, cats have no trouble getting the treats, but when presented with multiple strings, some of which are not connected to treats, the cats are unable to consistently choose the correct strings, leading to the conclusion that cats do not understand cause and effect in the same way that humans do.[18][19]
2011 (March 8) Elephant An article published by ABC Science suggests that, "elephants [are as] smart as chimps, [and] dolphins".[20]
2011 (June 29) Crow John Marzluff records that crows can hold a grudge.[21][22]
2011 (November 29) Raven "Ravens use gestures to communicate Before babies learn to speak, they communicate using gestures. Pointing at objects they want, for example. Outside of primates, this means of communication had never been observed in another species."[23]
2012 (September 17) In a test on New Caledonian crows, crows were placed in an enclosure wherein a stick would emerge from a hide. They used two scenarios: in the first, a human was observed entering the hide before the stick moved, and leaving after. In the second, the human remained hidden. In the first, the crows were much more relaxed after the human left, correctly linking the movement of the stick to the presence of the human. They would forage for food, and behave normally. In the second, the crow had no other reference for the stick's presence, so they remained wary. "These results really seem to be showing that crows react in a very similar way to humans in a situation that requires them to reason about a hidden causal agent," says biologist Alex Taylor."[24]
2014 Dolphin (long-finned pilot whale) It is shown for the first time that a species of dolphin, the long-finned pilot whale, has more neocortical neurons than any mammal studied to date including humans.[25]
2014 (April) Crow "Crows aren't driven purely by instinct - they can experience anticipation, and exercise self-control if the end result is a greater reward. A 2014 study devised a test based on the Stanford marshmallow experiment, a 1960s study into delayed gratification in children. The first step was to determine which snacks the crows liked the most. The researchers fed them grapes, bread, sausage, fried fat and other treats. Next, they were given a snack and the option to trade their snack - if they were willing to wait. They could either receive a better quality snack - meat in exchange for a grape, for instance - or a higher quantity of the same snack. The birds preferred to wait until a better snack was on offer, but if it was just more of the same, they weren't. In some cases, they waited up to 10 minutes for a better snack. The fact that they waited for better quality, not quantity, showed that they were waiting because they wanted to - not because they were actually hungry."[26][27]
2014 (July 23) Crow (New Caledonian "In an experiment with tubes published in PLOS One, scientists determined that New Caledonian crows can not only tell the difference between water and sand - they also understand water displacement. The test involved tubes containing water and a treat floating on top out of reach. The crows filled the tubes with enough rocks or other heavy items to bring the food within reach."[28][29][30]
2015 (October) Raven "In a 2015 study[31], researchers from the University of Vienna gave ravens a task wherein they would only receive the reward if they cooperated, pulling on ropes to raise a platform which had two pieces of cheese, one for each raven. If one raven stole their companion's cheese, as well as their own, they were on the outs: the other raven would refuse to cooperate with them - but they would cooperate with other ravens who played fair. "Such a sophisticated way of keeping your partner in check has previously only been shown in humans and chimpanzees, and is a complete novelty among birds," lead researcher Jorg Massen said."[32][27]
2016 (January) Florida scrub jay "Bebus et al. demonstrated that associative learning in Florida scrub-jays correlated with reversal learning, personality, and baseline hormone levels."[33]
2016 (February 2) Raven "A study released in early 2016 found that ravens possess something known as the Theory of Mind - that is, the ability to recognise mental states within themselves, and extrapolate that others have mental states, too, and that those mental states in others may differ from their own"[34]
2016 (Obtober) "A false-belief test is a comprehensive test used to test for an individual's theory of mind. Understanding language is a key component to being able to understand the directions for the false-belief test, and researchers have had to get creative to utilize this test in the research of non-human primates' theory of mind. Recent technology has enabled researchers to closely resemble the false-belief task without needing to use language. In Krupenye et al. (2016), an advanced eye-tracking technology was used to test for false-belief understanding in apes. The findings of this experiment showed that apes understood and accurately anticipated the behavior of an individual who held a false belief."[35]
2017 (June) Raven Researchers reveal that ravens are able to remember a human who cheated them out of a snack and were also more positive towards humans who exhibited fairer behaviour.[36]
2017 (June) Raven "Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month".[37]
2017 (July 14) Raven "When trained in the use of tools, ravens recognise the items as valuable and can set them aside against a future need. To figure this out, researchers trained ravens to release a treat by sticking a tool into a tube sticking out of a box."[38][39]
2018 (November) Parrot "A new study shows the African grey can perform some cognitive tasks at levels beyond that of 5-year-old humans. The results not only suggest that humans aren’t the only species capable of making complex inferences, but also point to flaws in a widely used test of animal intelligence."[40]
2020 (December 10) A study claims that by four months old, ravens have full-blown cognitive skills and before reaching full maturity they can rival adult great apes.[41]

Meta information on the timeline

How the timeline was built

The initial version of the timeline was written by FIXME.

Funding information for this timeline is available.

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What the timeline is still missing

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See also

External links

References

  1. ↑ 1.0 1.1 Vernouillet, Alizée (2018). "Social Intelligence Hypothesis". Encyclopedia of Animal Cognition and Behavior. Springer International Publishing: 1–5. doi:10.1007/978-3-319-47829-6_1498-1. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "Historical Perspective on Animal Cognition". connect.springerpub.com. Springer Publishing Company. 13 January 2021. Retrieved 8 October 2022. 
  3. ↑ Holleman, Gijs A.; Hooge, Ignace T. C.; Kemner, Chantal; Hessels, Roy S. (30 April 2020). "The 'Real-World Approach' and Its Problems: A Critique of the Term Ecological Validity". Frontiers in Psychology. 11: 721. doi:10.3389/fpsyg.2020.00721. 
  4. ↑ Smolker, Rachel; Richards, Andrew; Connor, Richard; Mann, Janet; Berggren, Per (26 April 2010). "Sponge Carrying by Dolphins (Delphinidae, Tursiops sp.): A Foraging Specialization Involving Tool Use?". Ethology. 103 (6): 454–465. doi:10.1111/j.1439-0310.1997.tb00160.x. 
  5. ↑ "Do Dolphins Eavesdrop on the Echolocation Signals of Conspecifics?" (PDF). escholarship.org. Retrieved 8 October 2022. 
  6. ↑ Agnew-Iowa, Sara (16 February 2015). "Pigeons are smarter than you'd think". Futurity. Retrieved 8 October 2022. 
  7. ↑ Povinelli, Daniel J.; Nelson, Kurt E.; Boysen, Sarah T. (1990). "Inferences about guessing and knowing by chimpanzees (Pan troglodytes).". Journal of Comparative Psychology. 104 (3): 203–210. ISSN 1939-2087. doi:10.1037/0735-7036.104.3.203. 
  8. ↑ Marten, Ken and Psarakos, Suchi "Using Self-View Television to Distinguish between Self-Examination and Social Behavior in the Bottlenose Dolphin (Tursiops truncatus)" (Consciousness and Cognition, Volume 4, Number 2, June 1995)
  9. ↑ Reiss, D; Marino, L (8 May 2001). "Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence". Proceedings of the National Academy of Sciences of the United States of America. 98 (10): 5937–42. PMC 33317Freely accessible. PMID 11331768. doi:10.1073/pnas.101086398. 
  10. ↑ Gallup Jr, Gordon G., and James R. Anderson. "Self-recognition in animals: Where do we stand 50 years later? Lessons from cleaner wrasse and other species." Psychology of Consciousness: Theory, Research, and Practice (2019).
  11. ↑ Healy, S. D.; Hurly, T. A. (1 March 1995). "Spatial memory in rufous hummingbirds (Selasphorus rufus): A field test". Animal Learning & Behavior. 23 (1): 63–68. 
  12. ↑ de Waal, Frans B.M. (August 2000). "Attitudinal reciprocity in food sharing among brown capuchin monkeys". Animal Behaviour. 60 (2): 253–261. doi:10.1006/anbe.2000.1471. 
  13. ↑ "Animals have complex dreams, MIT researcher proves". MIT News | Massachusetts Institute of Technology. Retrieved 12 October 2022. 
  14. ↑ Hare, Brian; Call, Josep; Tomasello, Michael (1 January 2001). "Do chimpanzees know what conspecifics know?". Animal Behaviour. 61 (1): 139–151. ISSN 0003-3472. doi:10.1006/anbe.2000.1518. 
  15. ↑ Hart, Benjamin L.; Hart, Lynette A.; McCoy, Michael; Sarath, C. R. (1 November 2001). "Cognitive behaviour in Asian elephants: use and modification of branches for fly switching". Animal Behaviour. 62 (5): 839–847. ISSN 0003-3472. doi:10.1006/anbe.2001.1815. 
  16. ↑ Brosnan, Sarah F.; de Waal, Frans B. M. (1 March 2002). "A proximate perspective on reciprocal altruism". Human Nature. 13 (1): 129–152. ISSN 1936-4776. doi:10.1007/s12110-002-1017-2. 
  17. ↑ Premack, David (28 August 2007). "Human and animal cognition: Continuity and discontinuity". Proceedings of the National Academy of Sciences. 104 (35): 13861–13867. doi:10.1073/pnas.0706147104. 
  18. ↑ "Cats outsmarted in psychologist's test". the Guardian. 16 June 2009. Retrieved 12 October 2022. 
  19. ↑ Pallaud, B. (1 July 1984). "Hypotheses on mechanisms underlying observational learning in animals". Behavioural Processes. 9 (4): 381–394. ISSN 0376-6357. doi:10.1016/0376-6357(84)90024-X. 
  20. ↑ "Elephants smart as chimps, dolphins". www.abc.net.au. 8 March 2011. Retrieved 12 October 2022. 
  21. ↑ Cornell, Heather N.; Marzluff, John M.; Pecoraro, Shannon (7 February 2012). "Social learning spreads knowledge about dangerous humans among American crows". Proceedings of the Royal Society B: Biological Sciences. 279 (1728): 499–508. doi:10.1098/rspb.2011.0957. 
  22. ↑ "Crows never forget a foe's face". www.abc.net.au. 29 June 2011. Retrieved 12 October 2022. 
  23. ↑ Pika, Simone; Bugnyar, Thomas (29 November 2011). "The use of referential gestures in ravens (Corvus corax) in the wild". Nature Communications. 2 (1): 560. ISSN 2041-1723. doi:10.1038/ncomms1567. Retrieved 12 October 2022. 
  24. ↑ Taylor, Alex H.; Miller, Rachael; Gray, Russell D. (2 October 2012). "New Caledonian crows reason about hidden causal agents". Proceedings of the National Academy of Sciences. 109 (40): 16389–16391. ISSN 0027-8424. doi:10.1073/pnas.1208724109. 
  25. ↑ Mortensen, Heidi S.; Pakkenberg, Bente; Dam, Maria; Dietz, Rune; Sonne, Christian; Mikkelsen, Bjarni; Eriksen, Nina (26 November 2014). "Quantitative relationships in delphinid neocortex". Frontiers in Neuroanatomy. 8: 132. ISSN 1662-5129. doi:10.3389/fnana.2014.00132. 
  26. ↑ Hillemann, Friederike; Bugnyar, Thomas; Kotrschal, Kurt; Wascher, Claudia A.F. (April 2014). "Waiting for better, not for more: corvids respond to quality in two delay maintenance tasks". Animal Behaviour. 90: 1–10. doi:10.1016/j.anbehav.2014.01.007. Check |doi= value (help). 
  27. ↑ 27.0 27.1 Starr, Michelle (9 November 2017). "13 Surprisingly Weird Reasons Why Crows And Ravens Are The Best Birds, No Question". ScienceAlert. Retrieved 12 October 2022. 
  28. ↑ Müller, J. J. A.; Massen, J. J. M.; Bugnyar, T.; Osvath, M. (1 June 2017). "Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month". Animal Behaviour. 128: 69–78. ISSN 0003-3472. doi:10.1016/j.anbehav.2017.04.004. 
  29. ↑ "Are ravens as smart as us? | BBC Earth". www.bbcearth.com. Retrieved 9 October 2022. 
  30. ↑ Logan, Corina J.; Jelbert, Sarah A.; Breen, Alexis J.; Gray, Russell D.; Taylor, Alex H. (23 July 2014). "Modifications to the Aesop's Fable Paradigm Change New Caledonian Crow Performances". PLOS ONE. 9 (7): e103049. ISSN 1932-6203. doi:10.1371/journal.pone.0103049. 
  31. ↑ Massen, Jorg J. M.; Ritter, Caroline; Bugnyar, Thomas (7 October 2015). "Tolerance and reward equity predict cooperation in ravens (Corvus corax)". Scientific Reports. 5: 15021. ISSN 2045-2322. doi:10.1038/srep15021. 
  32. ↑ "Ravens cooperate, but not with just anyone: Ravens detect cheaters in cooperation". ScienceDaily. Retrieved 12 October 2022. 
  33. ↑ Bebus, Sara E.; Small, Thomas W.; Jones, Blake C.; Elderbrock, Emily K.; Schoech, Stephan J. (1 January 2016). "Associative learning is inversely related to reversal learning and varies with nestling corticosterone exposure". Animal Behaviour. 111: 251–260. ISSN 0003-3472. doi:10.1016/j.anbehav.2015.10.027. 
  34. ↑ Bugnyar, Thomas; Reber, Stephan A.; Buckner, Cameron (2 February 2016). "Ravens attribute visual access to unseen competitors". Nature Communications. 7 (1): 10506. ISSN 2041-1723. doi:10.1038/ncomms10506. 
  35. ↑ Krupenye, Christopher; Kano, Fumihiro; Hirata, Satoshi; Call, Josep; Tomasello, Michael (7 October 2016). "Great apes anticipate that other individuals will act according to false beliefs". Science. 354 (6308): 110–114. ISSN 0036-8075. doi:10.1126/science.aaf8110. 
  36. ↑ Müller, J. J. A.; Massen, J. J. M.; Bugnyar, T.; Osvath, M. (1 June 2017). "Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month". Animal Behaviour. 128: 69–78. ISSN 0003-3472. doi:10.1016/j.anbehav.2017.04.004. 
  37. ↑ Müller, J. J. A.; Massen, J. J. M.; Bugnyar, T.; Osvath, M. (1 June 2017). "Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month". Animal Behaviour. 128: 69–78. ISSN 0003-3472. doi:10.1016/j.anbehav.2017.04.004. 
  38. ↑ Kabadayi, Can; Osvath, Mathias (14 July 2017). "Ravens parallel great apes in flexible planning for tool-use and bartering". Science. 357 (6347): 202–204. ISSN 0036-8075. doi:10.1126/science.aam8138. 
  39. ↑ Conroy, Gemma (13 July 2017). "Ravens Can Plan For The Future Like Humans And Apes". ScienceAlert. Retrieved 12 October 2022. 
  40. ↑ Writer, Peter Reuell Harvard Staff (25 February 2019). "Harvard study shows parrots can pass classic test of intelligence". Harvard Gazette. Retrieved 12 October 2022. 
  41. ↑ Pika, Simone; Sima, Miriam Jennifer; Blum, Christian R.; Herrmann, Esther; Mundry, Roger (10 December 2020). "Ravens parallel great apes in physical and social cognitive skills". Scientific Reports. 10 (1): 20617. ISSN 2045-2322. doi:10.1038/s41598-020-77060-8. 
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