Where Is the Cognizing in Comparative Cognition?
Abstract
Research in comparative cognition has increasingly focused on the evolutionary origins of cognitive variation. This approach has diversified the species studied and increased awareness of biological predispositions that affect cognition, but at the cost of dissociating comparative research from more mainstream cognitive science studies. Alternative approaches that focus more on basic principles can potentially foster a fresh rapprochement between human and animal cognition researchers. Studies of cognitive exotica, in particular, may yield important insights into how animals (including humans) cognize.
Keywords: animal cognition, anthropocentrism, cognitive ecology, cognitive plasticity
More than 30 years ago, Sara Shettleworth (1993) encouraged fellow researchers to forego studies focused on “other species doing things that people do” and to instead join the “ecological program” by studying cognitive problems that are “important in nature” (p. 179). At the time, researchers agreed that the value of comparing cognition across species came from the insights such comparisons could provide about cognitive evolution. As Riley and Langley (1993) succinctly put it, “The most important purpose of comparing species: discovering how animal minds have evolved” (p. 189). This goal remains dominant in modern studies of comparative cognition (Cantlon & Hayden, 2017; Crystal, 2021; Olmstead & Kuhlmeier, 2022; Vonk, 2021), although the term minds has largely been replaced by cognition. The ecological program has gained momentum and is widely perceived as successful, with recent reviews noting the broader range of species featured in publications today compared with the earlier hegemony of pigeon and rat studies (Brauer et al., 2020; Vonk, 2021). It is sobering to note, however, that Aristotle’s (350 B.C.E./1910) early cross-species comparisons of cognition included over 100 species, including more than 40 bird species, 20 different mammals, and several invertebrates, fish, and reptiles, such that current “progress” in species diversification could alternatively be viewed as a conceptual regress toward sorting similarities in the cognitive traits of animals. Few have critically assessed whether the ecological program is advancing scientific understanding of cognition. In this article, I argue that this approach has led to few significant scientific breakthroughs and potentially is counterproductive to understanding cognition, partly because it has failed to escape from its anthropocentric foundations and partly because it underestimates the contributions of individual experiences to variations in cognitive capacities.
Modern Variants of the Ecological Program
Modern approaches to mapping cognitive variations across species differ in many ways from the approach adopted by Aristotle. Most notably, developmental biologists can now track and control the genes that construct cognitive mechanisms (Rivi et al., 2023), in the tiniest of organisms (Boussard et al., 2021; Lyon et al., 2021). Technological advances have encouraged biologists to characterize the behavior of microscopic invertebrates in terms of cognitive processes, through observational and experimental studies of “basal cognition” (Lyon, 2019; Lyon et al., 2021). The premise underlying such efforts is that understanding natural cognition in simpler species can provide a foundation for understanding cognition in all organisms, including the evolutionary origins of cognitive variations across species. Activity in entire nervous systems (or precursors to nervous systems) can now be observed in parallel with organisms’ actions (Lovett-Barron, 2021), lifting the veil on previously hidden mechanisms. Within Shettleworth’s (2009) trichotomous division of cognitive processes into those fundamental, physical, or social, basal cognition studies heavily emphasize those viewed as fundamental.
At the other end of the spectrum, ecologically oriented studies of social cognitive processes typically focus on comparisons between primates and children (Santos & Rosati, 2015; Subiaul, 2016) or on studies of dog cognition (Hare & Tomasello, 2005; Miklósi, 2014). Anecdotal observations of dogs featured prominently in early debates about animal cognition (Morgan, 1896; Townshend, 2009). In fact, Aristotle (350 B.C.E./1910) felt that dogs (particularly females) were highly cognitively skilled because they could follow humans’ instructions. The scientific relevance of modern dog cognition research is often linked to the evolutionary insights such studies may provide (Hare & Tomasello, 2005). For instance, Katz and Huber (2018) noted, “From a fundamental scientific point of view, dogs are interesting because they provide a model for short-term cognitive evolution” (p. 333). Most studies of social cognitive evolution focus on identifying cognitive capacities that animals share with humans (e.g., Miklósi, 2014) or that are unique to humans (e.g., Johnston et al., 2017). This branch of the ecological program is thus unabashedly anthropocentric in its emphasis, blurring the line that Shettleworth (1993) originally drew between studies of natural cognition and what she called the “anthropocentric program.”
Limitations of Ecological Approaches to Studying Cognition
Ecological approaches to understanding animal cognition aim to “account for the whole panoply of evolved mechanisms that allow individuals of whatever species to adjust their behavior to features of their local environment” (Shettleworth, 2000, p. 57). These accounts of cognition consist mainly of proposed adaptive specializations (cognitive modules) that enable animals to solve specific problems by applying unique computations to task-contingent environmental inputs. Adaptive specializations are viewed as analogous to sensory modalities. Just as eyes are traits specialized for responding to light patterns, landmark-based navigation modules are (hypothetically) evolved cognitive traits specialized for responding to foraging impulses. Explaining cognition from an ecological perspective thus entails first identifying each species’ “Swiss Army knife” of cognitive traits, devising metrics for comparing species’ tools, and inferring evolutionary trajectories from observed similarities and differences. Ideally, this generates a taxonomy of cognitive traits mapped out phylogenetically, constituting a sort of cognitive cosmology or “cognology.” Pursuit of a cognology describing the evolutionary history of mentality is a major force underlying basal cognition research (Lyon et al., 2021). Unlike physical cosmology, however, basal cognitive research has generated few detailed predictions, surprising or otherwise. More generally, the ecological program has failed to produce any significant advances in our understanding of cognition and, for reasons detailed next, appears inadequate for generating any worthwhile cognology.
Psychometric measures of cognitive performance provide the foundation for the ecological program. Without precise and reliable metrics of cognitive differences, it is impossible to meaningfully compare cognitive traits across similar species (Figdor, 2022; Krasheninnikova et al., 2020). The adequacy of current psychometrics for describing such differences is questionable. For instance, Lea and Osthaus (2018) surveyed research on dog cognition in relation to “comparable” species (e.g., wolves, hyenas, dolphins, cats, horses) and concluded that dogs performed similarly to these other species. Their conclusion highlights several limitations of the ecological program. First, if current methods for assessing cognitive variations cannot distinguish the mental capacities of distantly related mammals, then it is doubtful that they can reliably differentiate cognitive traits in more similar species. Second, the criteria for deciding which cross-species comparisons are relevant are ill-defined (Krause, 2015; Range & Marshall-Pescini, 2022). Finally, intraspecies variations in cognition across different breeds, ages, sexes, localities, and lineages of dogs may easily be as large or larger than interspecies variations (Alberghina et al., 2023; Gnanadesikan et al., 2020) and can arise from many sources other than inherited genes, further complicating between-group comparisons and evolutionary inferences about cross-species similarities (Range & Marshall-Pescini, 2022).
Putting aside the difficulties of developing species-fair metrics of cognitive differences, the task of identifying which abilities depend on adaptive specializations raises several problems. Most notably, it is difficult to establish that any cognitive ability is subserved by dedicated circuits that do not critically contribute to other functions, or that did not originally evolve to serve some other purpose. Partly, this is because “cognitive traits” are inferred not observed and, in the case of the ecological program, inferred mainly from naturally occurring behaviors (Lyon et al., 2021). The main processes being emphasized (e.g., memory, anticipation, perception, problem-solving) are conceptual ancestors of pre-Aristotelian constructs used to describe human actions and experiences, making them intrinsically anthropocentric. Today, explaining all matter as a combination of air, earth, fire, and water is viewed as a hopelessly naïve approach, whereas explaining all cognition as a combination of memory, attention, perception, and thinking (the Aristotelian worldview) continues to be considered state of the art. How likely is it that Aristotle missed the boat when explaining physical phenomena but nailed it when explaining unobservable cognitive phenomena? As Narvaez and colleagues (2022) noted in a recent critique of evolutionary psychology, “Data, findings, and the theories that frame them are of inherently limited value when they emanate from flawed conceptual presuppositions” (p. 425).
Beyond the general methodological and conceptual limitations just noted, the ecological program faces serious empirical problems (Narvaez et al., 2022; Smith, 2020). Cognitive abilities are more dependent on epigenetic and environmental factors than was originally thought, and the computational properties of neural circuits are much less genetically determined. Consequently, the claim that species-specific neural circuits exist that map directly onto variations in hypothetical cognitive processes is dubious. Invertebrates use highly flexible neurochemical dynamics to control even the most basic motor patterns (Grashow et al., 2009; Marder et al., 2022), and processes of neurogenesis and brain plasticity enable cognitive mechanisms to develop in new ways with each generation, circumventing constraints of ancestral selection pressures.
Alternative Approaches to Understanding Cognitive Phenomena
Shettleworth (1993) noted two approaches to scientifically investigating cognition, which can be glossed as natural (ecological) and unnatural (psychological). Neither approach seems to have produced many transformational insights into how cognition works. For instance, changes in cognitive abilities across generations remain as mysterious now as they were 2,000 years ago (e.g., Bratsberg & Rogeberg, 2018). Some of the most intriguing discoveries about animals’ cognitive skills were serendipitous findings rather than theoretically predicted outcomes, such as the discoveries that dolphins can comprehend a gestural sign language (Herman et al., 1984), bonobos can comprehend spoken English (Savage-Rumbaugh et al., 1993), and chimpanzees can mentally encode spationumerical sequences (Inoue & Matsuzawa, 2007). Such capacities highlight the fact that cognizing in animals is experience dependent.
Understanding the nature of cognition requires not just cataloguing cognologies but also exploring what is cognitively possible. For example, Brainstetter et al. (2012) discovered that bottlenose dolphins can perform an auditory (echoic) recognition task nearly flawlessly, nonstop, day and night, for more than 2 weeks straight. From the perspective of human cognitive studies, this should be impossible. The chimpanzee Ai’s ability ability to track the spatial configurations of multiple Arabic numerals after viewing them for fractions of a second similarly seems incomprehensible on the basis of current models of working memory (Kawai & Matsuzawa, 2000). Although evolutionary just-so stories can explain why such capacities might exist, they provide no inkling of what happens when these species breeze through such artificial tasks. “Unnatural” experiments were required to reveal these capacities, and are needed to determine how they happen.
More than 2 centuries have passed since Spallanzani discovered that bats produce and perceive acoustic scenes that humans cannot (Dijkgraaf, 1960). Given that nonhuman animals monitor inputs that extend beyond the sensoria of humans, could it be that they also cognize in ways that are beyond humans’ abilities? The aforementioned findings from dolphins and chimpanzees compel that inference. Current scientific approaches are ill-suited for discovering such hidden abilities, however, and most existing theories presume that animal cognition is a subset of whatever humans can do. We simply do not know what determines the range of possible cognitive phenomena, nor what constrains cognitive capacity within or across species (Mercado, 2008). Defining cognition in terms of ancient, anthropocentric constructs and then sorting observed actions on the basis of these intuitions is unlikely to promote progress in understanding cognition in any species, including humans.
The periodic table of elements was not developed through observations of naturally created materials or by sorting matter according to categories proposed by Aristotle. Its development required recognition that the invisible element hydrogen was “special,” that there were patterns in properties predictable from ordering known elements on the basis of their atomic masses, and that unknown elements should exist with properties related to, but distinct from, those that were naturally found. These insights were inconceivable and undiscoverable through the observational/inference-based approaches favored by Aristotle. When cognitive studies are ineffectual at generating new insights, they run the risk of shifting from science to infotainment. For comparative cognitive research to advance, researchers need to embrace the likely possibility that their current categories, inferences, and assumptions are inadequate to the task of understanding how cognition works (or varies) across species. Future studies of animal cognition can lead to profound transformations in the scientific understanding of how minds work, but such advances seem improbable if researchers continue to focus their efforts on mapping out the evolutionary origins of hypothetical cognitive traits. It is time to extend the search beyond preconceived cognitive processes and ill-conceived adaptive specializations.
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