Colombo, Michael

Scarf, Damian

Zentall, Thomas R.

English

University of Kentucky

University of Kentucky UKnowledge Psychology Faculty Publications Psychology 2-10-2021 The Comparative Psychology of Intelligence: Macphail Revisited Michael Colombo University of Otago, New Zealand Damian Scarf University of Otago, New Zealand Thomas R. Zentall University of Kentucky, zentall@uky.edu Follow this and additional works at: https://uknowledge.uky.edu/psychology_facpub  Part of the Psychology Commons Right click to open a feedback form in a new tab to let us know how this document benefits you. Repository Citation Colombo, Michael; Scarf, Damian; and Zentall, Thomas R., "The Comparative Psychology of Intelligence: Macphail Revisited" (2021). Psychology Faculty Publications. 200. https://uknowledge.uky.edu/psychology_facpub/200 This Editorial is brought to you for free and open access by the Psychology at UKnowledge. It has been accepted for inclusion in Psychology Faculty Publications by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. The Comparative Psychology of Intelligence: Macphail Revisited Digital Object Identifier (DOI) https://doi.org/10.3389/fpsyg.2021.648782 Notes/Citation Information Published in Frontiers in Psychology, v. 12, article 648782. © 2021 Colombo, Scarf and Zentall This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. This editorial is available at UKnowledge: https://uknowledge.uky.edu/psychology_facpub/200 EDITORIALpublished: 10 February 2021doi: 10.3389/fpsyg.2021.648782Frontiers in Psychology | www.frontiersin.org 1 February 2021 | Volume 12 | Article 648782Edited and reviewed by:Sarah Till Boysen,Independent Researcher, Sunbury,United States*Correspondence:Michael Colombocolombo@psy.otago.ac.nzSpecialty section:This article was submitted toComparative Psychology,a section of the journalFrontiers in PsychologyReceived: 01 January 2021Accepted: 19 January 2021Published: 10 February 2021Citation:Colombo M, Scarf D and Zentall T(2021) Editorial: The ComparativePsychology of Intelligence: MacphailRevisited. Front. Psychol. 12:648782.doi: 10.3389/fpsyg.2021.648782Editorial: The ComparativePsychology of Intelligence: MacphailRevisitedMichael Colombo 1*, Damian Scarf 1 and Tom Zentall 21Department of Psychology, University of Otago, Dunedin, New Zealand, 2Department of Psychology, University of Kentucky,Lexington, KY, United StatesKeywords: Macphail, null hypothesis, comparative cognition, intelligence, species differencesEditorial on the Research TopicThe Comparative Psychology of Intelligence: Macphail RevisitedIn a series of papers in the 80s, Macphail (1982, 1985, 1987) put forth evidence in support ofthe Null Hypothesis for differences in intelligence across non-human species, stating in his 1985paper that there are “no differences, either qualitative or quantitative, among vertebrates” (p. 46).He further claimed that association formation dominates intelligent behavior, that any differencesin intelligence between species could be accounted for by the differential effects of contextualvariables, that learning mechanisms are of general applicability and did not evolve as species-specific specializations, and that human intelligence differs from that of other animals in that onlyhumans possess a species-specific language device.The peer commentaries onMacphail’s (1987) Behavioral and Brain Sciences paper were generallynegative. The most scathing comment was from Goldman-Rakic and Preuss (1987) who suggestedthat “Macphail’s ‘null hypothesis’ is merely the epitaph on the head stone of comparative cognition”(p. 667). Surprisingly, despite the negative tone, Macphail (1987) ended his response to thecommentaries on an uplifting note, stating that “For my part, I remain an optimist, and preferto see the failure to demonstrate differences as evidence not that our scientific procedures areweak but that the animal mind is not what we expected it to be. And after all, did we reallyexpect that it would be?” (p. 688). Based on the growth of comparative cognition in the more thanthree decades since Macphail’s (1987) paper, and the papers included in this Research Topic, it isclear Macphail was right to be optimistic. As Pepperberg notes, Macphail (1987) should be givencredit for “. . . instigating a variety of controversies, stimulating the wide-ranging discussions, andgenerating the types of challenges that have led to many new avenues of research” (p. 10).At the time, many of the remarkable abilities of non-human animals were unknown toMacphail.Abilities such as episodic memory, theory of mind, orthographic processing, planning for thefuture, fast mapping, and numerical competence, to name but a few, were yet to have their time inthe limelight.With the wealth of comparative data collected over the past 30 years, we thought it wastimely to review the status of Macphail’s Null Hypothesis, and gauge how the current generation ofcomparative psychologists approach the inherent challenge that Macphail put forward.The manuscripts we received ranged from empirical to theoretical, and covered research ona variety of different animals such as pigeons, fish, rats, humans, parrots, eels, crows, monkeys,marine mammals, and spiders. All the papers addressed Macphail’s main claim that there are noqualitative or quantitative differences in intelligence across species. A subset of papers addressedMacphail’s other claims that (1) contextual variables can explain all of the observed differencesbetween species, (2) associative processes account for all non-human intelligence, and (3) theuniqueness of human intelligence is due to a species-specific language acquisition device.Colombo et al. Editorial: Macphail RevisitedQUALITATIVE AND QUANTITATIVEDIFFERENCESIssues of the definition of intelligence aside, virtually all ofthe manuscripts supported Macphail’s view that there are noqualitative differences in intelligence across animals. Whetherit is orthographic processing in pigeons (Scarf and Colombo)numerical competence in pigeons, crows, and fish (Scarf andColombo; Nieder; Petrazzini et al.), counterintuitive features ofskill learning in rats (Reid and Swafford), planning in humans(Martin-Ordas), syntactic abilities in parrots (Pepperberg),spatial learning in eels (Watanabe), working memory in crows(Hahn and Rose), the irrational choices of pigeons and humans(Stagner et al.; Zentall), equivalence relations (Colombo andScarf; Zentall), a variety of other abilities in marine mammals(Bauer et al.) and birds (Bastos and Taylor; Zentall), tool use(Cabrera-Álvarez and Clayton), predatory strategies in spiders(Cross et al.), or complex sequential behavior in rats, mice,pigeons, and humans (Fountain et al.), not to mention a host ofother sophisticated behaviors alluded to in many of these papersthat have been conducted over the past three and a half decades,all vertebrates seem capable of displaying behaviors that wereonce considered the domain of only humans or, at most, non-human primates. On the issue of qualitative differences, whatmight easily be considered the core thrust of the Null Hypothesis,Macphail was nothing short of prescient.While there was consensus regarding the absence ofqualitative differences across species, the majority of the paperswere in favor of rejecting Macphail’s Null Hypothesis withrespect to no quantitative differences across species. The issueof quantitative differences is difficult and depends, of course,on how one chooses to define “quantitative.” Macphail (1985)defined a quantitative difference as “. . . one species used amechanism or mechanisms common to both species moreefficiently than the other, and this might be reflected in afaster rate of solution or better asymptotic performance. . . ” (p.38). If defined by asymptotic performance, the fact that theperformance of animals on tasks of orthographic processing andnumerical competence (Scarf and Colombo), syntactic abilities(Pepperberg), and tool use (Cabrera-Álvarez and Clayton) arecomparable between distantly related species (namely birds andprimates) lends supports to Macphail’s view that there may noteven be quantitative differences across species. Cross et al. takethis one step further by suggesting that there are even comparablepredatory strategies between vertebrate species and spiders (i.e.,a non-vertebrate species). That said, most of the papers in theResearch Topic accepted that quantitative differences do existbetween species, especially if one takes Macphail’s definition of“quantitative” as measured by faster rates of solution, or moreefficient use of an ability, a vague term that might better be castas greater flexibility in the use of an ability.ROLE OF CONTEXTUAL VARIABLESMost of the papers also agree that contextual variables can explainmany of the observed differences in abilities across species. Thecase for the importance of contextual variables was made moststrongly by Colombo and Scarf who showed that with respectto a number of tasks, when contextual variables are properlyaccounted for, qualitative differences that have been observedacross different animals vanish. Schubiger et al. presented anenormous list of potential contextual variables, both subject-related and task-related, supporting the possibility that onceconsidered, evidence of even quantitative differences may vanishas well.THE ROLE OF ASSOCIATIONS AND THEUNIQUENESS OF HUMAN INTELLIGENCEAlthough few, some papers also tackled Macphail’s (1987)claims that association formation underlies intelligence and theuniqueness of human language. With respect to associationformation, there were those that supported the idea thatassociation processes underlie cognitive behavior (Scarf andColombo; Colombo and Scarf), and those that disagreed thatcognitive behavior is guided by associative processes (Bastos andTaylor). There seems little doubt that associative processes areuniversal. Whether Macphail was correct when he stated thatassociation formation dominates intelligent behavior hinges, asso many commentaries in his 1987 paper raised, on how onedefines “intelligence.” Bauer et al. were correct when they statedthat “In many ways, ‘intelligence’ seems to be a folk psychologyterm that maps poorly on natural psychological and biologicalprocesses, and therefore, lends itself to a wide range of often-inconsistent interpretations” (p 14). Whether behaviors extendbeyond associative process is a complex topic. In his typicallyprescient manner, Macphail (1987) forestalled this issue whenhe stated that “The problem is that we do not understand whatprocesses underlie. . . complex behavior” (p. 683).On the topic of language, countering Macphail’s (1987) claimof a species-specific language acquisition device that sets humansapart from other animals, Corballis elegantly highlights thefact that language is now recognized as an amalgam of severalabilities (e.g., mental time travel, theory of mind, etc.), manywhich are present to varying degrees in non-human animals.Further, according to Corballis, it is unlikely that the hierarchicaland generative aspects of thought are even unique to humans.Petrazzini et al. echoed similar sentiments in their paper. Thus,if anything, it would seem that Macphail erred on the side ofcaution with his Null Hypothesis, as it appears that even languagemay not be a dividing line between humans and non-humans.THEORETICAL ISSUESA number of papers also addressed a variety of theoreticalissues around the notion of a Null Hypothesis. Petrazzini et al.called into question how we assess the presence vs. absence ofdifferences between species. Traditionally, in keeping with itsnamesake, Macphail’s Null Hypothesis is assessed by rejecting orfailing to reject the null hypothesis based on a p-value. Petrazziniet al. argued for finer comparative methodologies such as aBayesian approach, which would evaluate the relative strengthFrontiers in Psychology | www.frontiersin.org 2 February 2021 | Volume 12 | Article 648782Colombo et al. Editorial: Macphail Revisitedof two competing hypotheses. Similarly, Bastos and Taylor alsosuggested a Bayesian framework to distinguish between supportfor the Null Hypothesis and a lack of statistical power. Taking thisone step further, even when paired with null-hypothesis testing,Bayes factor could be made mandatory for comparative papers,allowing a measure of confidence in any null findings.Finally, Hahn and Rose argue that working memory is acritical component of cognitive abilities, and that a better wayto compare species is to use their working memory capacityand retention limits as a proxy for their cognitive abilities.“Differences and similarities in WM (e.g., in its capacity) mayoffer insights into why some animals may be (un-)able (sic) todisplay certain cognitive behaviors. Macphail’s null-hypothesiscan thus be investigated in the light of potentially qualitative,and quantitative differences of a fundamental trait of cognition”(p. 2).CONCLUSIONSIn light of the results of research over the past 30 years, Macphail’shypothesis that all vertebrates have similar cognitive capacitiesmay not be as implausible as it may have at appeared at the time.In order to conclude that there are qualitative or quantitativedifferences among species, however, one must first eliminateimportant differences in contextual variables concerned withperception, motor skills, and motivation. If nothing else,Macphail’s proposition has served as encouragement and avaluable challenge to comparative researchers to conduct welldesigned tests of the abilities of a large number of animal species.Fountain et al. are correct when they say that “. . .Macphail’sclaim continues to challenge all empiricists and theoriststo consider the power of even simple neural systems toaccount for animals’ ability to encode simplicity in terms ofneural representation from the complexity of the surroundingenvironmental milieu” (p. 3). With respect to the otherissues that Macphail raised, such as whether species differquantitatively and whether association formation dominatesintelligent behavior, Macphail (1987) provided a roadmapas to how the field of comparative cognition can advanceour understanding of the human mind by stating that “Iexpress the hope that workers seeking to disprove the nullhypothesis will attempt to devise novel tasks for comparativework—tasks which associative devices could not solve”(p. 683).There is much that the field of comparative cognition owesto Macphail. Corballis stated it perfectly when he said that“Macphail’s writing set up the challenge, and attempting toanswer it can only advance our knowledge of how animals think,and where humans fit into the overall scheme of things” (p. 8).AUTHOR CONTRIBUTIONSMCwrote the first draft. DS and TZ reviewed and edited the draft.All authors approved the work for publication.REFERENCESGoldman-Rakic, P. S., and Preuss, T. M. (1987). Wither comparative psychology?Behav. Brain Sci. 10, 666–667.Macphail, E. (1982). Brain and Intelligence in Vertebrates. Clarendon Press.Macphail, E. M. (1985). Vertebrate intelligence: the null hypothesis. Philos.Trans.R. Soc. Lond. Ser. B Biol. Sci. 308, 37–51.Macphail, E. M. (1987). The comparative psychology of intelligence. Behav. BrainSci. 10, 645–695.Conflict of Interest: The authors declare that the research was conducted in theabsence of any commercial or financial relationships that could be construed as apotential conflict of interest.Copyright © 2021 Colombo, Scarf and Zentall. This is an open-access articledistributed under the terms of the Creative Commons Attribution License (CC BY).The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) and the copyright owner(s) are credited and that the originalpublication in this journal is cited, in accordance with accepted academic practice.No use, distribution or reproduction is permitted which does not comply with theseterms.Frontiers in Psychology | www.frontiersin.org 3 February 2021 | Volume 12 | Article 648782

The Comparative Psychology of Intelligence: Macphail Revisited

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1200&context=psychology_facpub

The Comparative Psychology of Intelligence: Macphail Revisited

Abstract

Similar works

Full text

Available Versions

University of Kentucky