Comparative Vertebrate Cognition. Are primates superior to non-primates?

Lesley J. Rogers and Gisela Kaplan, Eds. (2004)

Kluwer Academic/ Plenum Publishers; London.

ISBN 0-306-47727-0 (hardback) EUR 126.00 / £87.00 / $140.00

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Are primates superior?  The readership of Primate Eye might be expected to shout together with a loud and jocular yes to a question that many ethologists, zoologists and evolutionary and cognitive scientists must have asked themselves and their colleagues many times.  Historically, studies of cognition in non-human animals have largely concentrated on primates (apes and monkeys in particular) or archetypal lab animals (the familiar rats and pigeons) and this fascination with primate cognition undoubtedly stems from the premise that primates are special, because we are primates.  But in recent years, the study of cognition in other animal taxa has gained momentum and we are now better placed than ever to ask if the order Primates really is superior, beyond being the group within which humans evolved. 

Comparative Vertebrate Cognition aims to answer this question, or at least to consider and draw attention to what we know so far and assess the new research directions that are required, so that we can answer the question in the future.  The book is divided into five sections: complex cognition; social learning; communication; theory of mind; and brain, evolution and hemispheric specialisation.  The first section comprises chapters by Nathan Emery and Nicola Clayton, and Giorgio Vallortigara.  Emery and Clayton (Chapter 1) begin their chapter with a summary of seven claims that they argue are the basis for the special status of primates.  They then argue that each of these claims can also be applied to certain bird species, with the evidence mainly concentrating on corvids and parrots.  After a discussion of the “perils of primatocentrism”, they make a convincing argument for convergent cognitive evolution between corvids, parrots and primates. 

Vallortigara (Chapter 2) offers an extensive and well-rounded view of research into visual representation in birds and primates.  The conclusion cautiously suggests that there might be more similarities between the visual cognition of birds and primates than differences, although some distinctions obviously exist. Vallortigara also makes the important observation that we should expect independent evolution of computationally similar cognitive mechanisms when animals are faced with “basically similar problems”.

In the first of the Social Learning chapters, Hilary Box and Anne Russon (Chapter 3) review evidence of imitation and behavioural traits as studied in monkeys and apes, arguing that studies are most productive when they concentrate on the mechanisms and functions of social learning in different ecological contexts, as opposed to making generalisations about mechanisms based on phylogeny.  Extending this sentiment, Yfke van Bergen, Kevin Laland and William Hoppitt present a consideration of innovation and social learning in fish, particularly the guppy (Poecilia reticulata) (Chapter 4).  They remind us that explanations of social learning should depend only on the behaviour observed, rather than on the relatedness to humans of the observed species.

John Newman (Chapter 5) begins the Communication section of the book with a discussion of primate isolation calls.  Through developmental, functional, neurological and pharmacological comparisons, he well illustrates the number of different ways behaviour can be studied, and concludes that isolation calls are a trait conserved across mammals and are not special within the Primate order.  The second Communication chapter by Gisela Kaplan (Chapter 6) reviews meaningful communication in primates, birds and other animals and considers the link between signal complexity and higher cognitive abilities, concluding that great apes are not alone among animals in exhibiting complex communicative abilities such as referential signalling. 

The Theory of Mind section of the book begins with the presentation by Moti Nissani (Chapter 7) of new data on elephant cognition.  The chapter describes two series of experiments, the first of which explore the elephants’ understanding of what humans can see, and compares their performance with that of adult chimpanzees.  The second series investigates whether elephants possess insightful problem-solving skills.  Although the sample sizes are small, with only two elephants participating in the studies, the results are intriguing and confirm that elephant cognition merits further consideration.

Josep Call (Chapter 8) continues the discussion of understanding what others can see with a well-balanced and concise review of research into the use of social information in dogs and chimpanzees.  He concentrates on three main areas of social information: reading attention; following attention; and directing attention.  Call’s final statement that it is important to scrutinise the mechanisms of even apparently simple behaviours (rather than assuming that such behaviours may rely on simple mechanisms such as conditioning) is advice that we surely cannot afford to ignore when striving to understand animal cognition.   

Lesley Rogers (Chapter 9) explores the assumption that increased brain size equates to increased cognitive abilities, and discusses how species differences in the size of brain regions or systems may have arisen.  The conclusion, that advanced cognition does not have to depend on the existence of a neocortex, echoes that of Emery and Clayton in chapter 1.  The volume ends with a discussion by Michelle Hook (Chapter 10) of the evolution of lateralised motor functions in primate and non-primate mammals, birds and lower vertebrates.  The specialisation of the left hemisphere for communication seems to be highly conserved throughout evolution, and she concludes that many species, not just primates, can represent interesting models for investigating the evolution of hemisphere lateralisation.   

A criticism that can be levelled against this book is that it suffers from rather selective referencing in parts.  Perhaps it is to be expected in a volume such as this that some chapter authors will appear to have an axe to grind, but in discussions of higher cognitive processing at least three chapters fail to cite recent advances in the study of theory of mind in primates.  In these chapters only older, less well-designed studies of primates are mentioned.  These omissions are all the more noteworthy because citations of even more recent papers relating to similar questions in other animals are present.

Overall, Comparative Vertebrate Cognition is a very enlightening and timely book.  It is an interesting and thought provoking attempt to draw attention to an area that is still in the early stages of its rise to scientific popularity, and draws on a wide range of research topics and an impressive range of species.  Whilst the aim of the book was simple - to assess the evidence concerning cognitive abilities in primate and non-primate species – it is anything but a simple question.  Many of the authors wisely cautioned the reader against making generalisations about whole orders of animals, and as Vallortigara suggested at the end of chapter 2, it is perhaps not likely that the differences revealed between animals will lead to a conclusion of an overall superiority of one taxon. 

The sub-title of the book is obviously designed to spark a reaction and inform the reader as to the premise of the book, but the suggestion by some authors that primatologists assert that the primate order is superior was a little contrived.  Primates are studied extensively, and this is surely based, to some extent at least, on the inclusion of humans in the order.  Yes, this makes primates inherently interesting, but not necessarily superior.  Wouldn’t even the most ardent primatologists agree that all animals are interesting if interesting questions are asked of them, and the current, long overdue, trend to widen the scope of comparative cognition studies can only be a good thing.  Are primates really superior?  We all have an opinion, but this text should inspire much more research that will contribute to a fuller answer.

Lucy Bates

University of St Andrews