| 1. |
- Bshary, Redouan, et al.
(författare)
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Fish ecology and cognition : insights from studies on wild and wild-caught teleost fishes
- 2022
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Ingår i: Current Opinion in Behavioral Sciences. - : Elsevier BV. - 2352-1546. ; 46
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Tidskriftsartikel (refereegranskat)abstract
- Over the last decades, we witnessed a growing interest in animal cognition, in general, and in fish cognition, in particular. Here, we provide various study examples that employ an ecological approach to study cognition through field observations, field manipulations and laboratory tests on wild teleost fishes. In this review, we focus on cases with implications for understanding endotherm vertebrate cognition, that is, cases that show fishes possess supposedly ‘complex’ cognitive processes originally thought to warrant a more complex brain. Furthermore, in contrast to the classic interpretation of high/low performance as high/low cognitive abilities, incorporating an individual-level ecological approach reveals that low performance in a cognitive task may be caused by a mismatch between the experimental paradigm and the individual’s experience. The future avenue for wild fish cognition is to grasp better how individual, population and species differences in performance stem from differences in their ecological conditions.
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| 2. |
- Bshary, Redouan, et al.
(författare)
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Pairs of cooperating cleaner fish provide better service quality than singletons.
- 2008
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 455:7215, s. 964-6
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Tidskriftsartikel (refereegranskat)abstract
- Service providers may vary service quality depending on whether they work alone or provide the service simultaneously with a partner. The latter case resembles a prisoner's dilemma(1-4), in which one provider may try to reap the benefits of the interaction without providing the service. Here we present a game- theory model based on the marginal value theorem(5), which predicts that as long as the client determines the duration, and the providers cooperate towards mutual gain, service quality will increase in the pair situation. This prediction is consistent with field observations and with an experiment on cleaning mutualism, in which stable male - female pairs of the cleaner wrasse Labroides dimidiatus repeatedly inspect client fish jointly. Cleaners cooperate by eating ectoparasites(6) off clients but actually prefer to cheat and eat client mucus(7). Because clients often leave in response to such cheating, the benefits of cheating can be gained by only one cleaner during a pair inspection. In both data sets, the increased service quality during pair inspection was mainly due to the smaller females behaving significantly more cooperatively than their larger male partners. In contrast, during solitary inspections, cleaning behaviour was very similar between the sexes. Our study highlights the importance of incorporating interactions between service providers to make more quantitative predictions about cooperation between species.
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| 3. |
- Demairé, Camille, et al.
(författare)
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Reduced access to cleaner fish negatively impacts the physiological state of two resident reef fishes
- 2020
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 167:4
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Tidskriftsartikel (refereegranskat)abstract
- Many client coral reef fishes have their ectoparasites removed by the cleaner wrasse Labroides dimidiatus in mutualistic interactions. Clients regularly receiving cleaning services reportedly benefit from increased growth and cognitive performance, but the underlying physiological changes that covary with such benefits are unknown. Here, we tested whether reduced access to cleaning services affects physiological state in two species of damselfish, Amblyglyphidodon curacao and Acanthochromis polyacanthus. We performed an in situ removal experiment on the Great Barrier Reef, Australia, whereby 47% of cleaners on a natural reef were removed. Since cleaners occupy defined territories (called cleaning stations), this removal created areas where small, resident clients, including A. polyacanthus and A. amblyglyphidodon, had no access to cleaning services. One month following cleaner removal, we measured body condition and collected blood samples from both damselfish species from territories with and without access to cleaners. Blood was used for estimating haematocrit levels, hormonal analyses, and immune cell counts. We tested for correlations among all these parameters to explore potential trade-offs in terms of growth, aerobic capacity, immune activation, and/or reproduction as a result of the loss of cleaning benefits. In both species, we found that fish without access to cleaners had lower haematocrit, testosterone levels, and lymphocyte counts than fish with access. There were no significant changes in fish body condition, leukocytes, granulocytes, or plasma cortisol levels between fish with access to cleaners or not. However, testosterone levels correlated negatively with the proportion of granulocytes in the blood of fish with access to cleaners. Our results suggest that even a relatively short-term reduction in access to cleaning services can have negative physiological outcomes for clients. Thus, the presence of cleaners on coral reefs appears to have important benefits for coral reef fish community health.
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| 4. |
- Leimar, Olof, 1949-, et al.
(författare)
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Effects of local versus global competition on reproductive skew and sex differences in social dominance behaviour
- 2022
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 289:1987
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Tidskriftsartikel (refereegranskat)abstract
- Social hierarchies are often found in group-living animals. The hierarchy position can influence reproductive success (RS), with a skew towards high-ranking individuals. The amount of aggression in social dominance varies greatly, both between species and between males and females within species. Using game theory we study this variation by taking into account the degree to which reproductive competition in a social group is mainly local to the group, emphasizing within-group relative RS, or global to a larger population, emphasizing an individual's absolute RS. Our model is similar to recent approaches in that reinforcement learning is used as a behavioural mechanism allowing social-hierarchy formation. We test two hypotheses. The first is that local competition should favour the evolution of mating or foraging interference, and thus of reproductive skew. Second, decreases in reproductive output caused by an individual's accumulated fighting damage, such as reduced parenting ability, will favour less intense aggression but should have little influence on reproductive skew. From individual-based simulations of the evolution of social dominance and interference, we find support for both hypotheses. We discuss to what extent our results can explain observed sex differences in reproductive skew and social dominance behaviour.
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| 5. |
- Leimar, Olof, 1949-, et al.
(författare)
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Flexible learning in complex worlds
- 2024
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Ingår i: Behavioral Ecology. - 1045-2249 .- 1465-7279. ; 35:1
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive flexibility can enhance the ability to adjust to changing environments. Here, we use learning simulations to investigate the possible advantages of flexible learning in volatile (changing) environments. We compare two established learning mechanisms, one with constant learning rates and one with rates that adjust to volatility. We study an ecologically relevant case of volatility, based on observations of developing cleaner fish Labroides dimidiatus that experience a transition from a simpler to a more complex foraging environment. There are other similar transitions in nature, such as migrating to a new and different habitat. We also examine two traditional approaches to volatile environments in experimental psychology and behavioral ecology: reversal learning, and learning set formation (consisting of a sequence of different discrimination tasks). These provide experimental measures of cognitive flexibility. Concerning transitions to a complex world, we show that both constant and flexible learning rates perform well, losing only a small proportion of available rewards in the period after a transition, but flexible rates perform better than constant rates. For reversal learning, flexible rates improve the performance with each successive reversal because of increasing learning rates, but this does not happen for constant rates. For learning set formation, we find no improvement in performance with successive shifts to new stimuli to discriminate for either flexible or constant learning rates. Flexible learning rates might thus explain increasing performance in reversal learning but not in learning set formation, and this can shed light on the nature of cognitive flexibility in a given system. Animals need to adjust to changes that occur in their environment, such as new food types becoming available or old food types becoming unsuitable. Learning about these changes could be essential for success, in particular, if the environment is complex, with many things to learn about. When changes happen, it might be advantageous to quickly learn about new things. We use computer simulations of learning to investigate how big the advantage might be.
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| 6. |
- Leimar, Olof, 1949-, et al.
(författare)
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Reproductive skew, fighting costs and winner-loser effects in social dominance evolution
- 2022
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 91:5, s. 1036-1046
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Tidskriftsartikel (refereegranskat)abstract
- Social hierarchies are often found in group-living animals and can be formed through pairwise aggressive interactions. The dominance rank can influence reproductive success (RS) with a skew towards high-ranking individuals.Using game theory, we investigate how the opportunity for differently ranked individuals to achieve RS influences the costs of hierarchy formation and the strength of winner and loser effects.In our model, individuals adjust their aggressive and submissive behaviour towards others through reinforcement learning. The learning is based on rewards and penalties, which depend on relative fighting ability. From individual-based simulations, we determine evolutionary equilibria of traits such as learning rates. We examine situations that differ in the extent of monopolisation of contested RS by dominants and in the proportion of total RS that is contested.The model implements two kinds of fighting costs: a decrease in effective fighting ability from damage (loss of condition) and a risk of mortality that increases with the total accumulated damage. Either of these costs can limit the amount of fighting.We find that individuals form stable dominance hierarchies, with a positive correlation between dominance position and fighting ability. The accumulated costs differ between dominance positions, with the highest costs paid by low or intermediately ranked individuals. Costs tend to be higher in high-skew situations.We identify a ‘stay-in, opt-out’ syndrome, comprising a range from weaker (stay-in) to stronger (opt-out) winner–loser effects. We interpret the opt-out phenotype to be favoured by selection on lower ranked individuals to opt out of contests over social dominance, because it is more pronounced when more of the total RS is uncontested.We discuss our results in relation to field and experimental observations and argue that there is a need for empirical investigation of the behaviour and reproductive success of lower ranked individuals.
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| 7. |
- Leimar, Olof, 1949-, et al.
(författare)
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Social bond dynamics and the evolution of helping
- 2024
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 120:11
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Tidskriftsartikel (refereegranskat)abstract
- Empiricists often struggle to apply game theory models to real-life cases of animal cooperation. One reason is that many examples of cooperation occur in stable groups, where individuals form social bonds that influence exchanges of help in ways that are not well described by previous models, including the extent of reciprocity and how relationships are initiated. We present a game theory model exploring the conditions under which social bonds between group members promote cooperation. In the model, bonds build up from exchanges of help in a similar way as the strength of association increases in learning, as in the Rescorla–Wagner rule. The bonds in turn affect partner choice and influence helping amounts. The model has a mechanism of reciprocity for bonded pairs, which can evolve toward either loose or strict reciprocation. Several aspects of the model are inspired by observations of food sharing in vampire bats. We find that small social neighborhoods are required for the evolutionary stability of helping, either as small group sizes, or if bonded members of larger groups can form temporary (daily) smaller groupings. The costs of helping need to be fairly low, while the benefits can be substantial. The form of reciprocity that evolves is neither immediate nor very strict. Individuals in need request help based on bond strength, but there is also an evolved preference for initiating bonds with new group members. In contrast, if different groups come into temporary contact, the evolved tendency is to avoid forming bonds between groups.
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| 8. |
- Manrique, Hector M., et al.
(författare)
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The psychological foundations of reputation-based cooperation
- 2021
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8436 .- 1471-2970. ; 376:1838
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Forskningsöversikt (refereegranskat)abstract
- Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here, we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others mental states (which allows for perspective-taking and attribution of intentions) and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation. This article is part of the theme issue The language of cooperation: reputation and honest signalling.
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| 9. |
- Quinones, Andres E., et al.
(författare)
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Reinforcement Learning Theory Reveals the Cognitive Requirements for Solving the Cleaner Fish Market Task
- 2020
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 195:4, s. 664-677
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Tidskriftsartikel (refereegranskat)abstract
- Learning is an adaptation that allows individuals to respond to environmental stimuli in ways that improve their reproductive outcomes. The degree of sophistication in learning mechanisms potentially explains variation in behavioral responses. Here, we present a model of learning that is inspired by documented intra- and interspecific variation in the performance of a simultaneous two-choice task, the biological market task. The task presents a problem that cleaner fish often face in nature: choosing between two client types, one that is willing to wait for inspection and one that may leave if ignored. The cleaner's choice hence influences the future availability of clients (i.e., it influences food availability). We show that learning the preference that maximizes food intake requires subjects to represent in their memory different combinations of pairs of client types rather than just individual client types. In addition, subjects need to account for future consequences of actions, either by estimating expected long-term reward or by experiencing a client leaving as a penalty (negative reward). Finally, learning is influenced by the absolute and relative abundance of client types. Thus, cognitive mechanisms and ecological conditions jointly explain intra- and interspecific variation in the ability to learn the adaptive response.
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| 10. |
- Roberts, Gilbert, et al.
(författare)
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The benefits of being seen to help others: indirect reciprocity and reputation-based partner choice
- 2021
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8436 .- 1471-2970. ; 376:1838
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Forskningsöversikt (refereegranskat)abstract
- When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans. This article is part of the theme issue The language of cooperation: reputation and honest signalling.
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| 11. |
- Roche, Dominique G., et al.
(författare)
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Behavioural lateralization in a detour test is not repeatable in fishes
- 2020
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 167, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Behavioural lateralization, the asymmetric expression of cognitive functions, is reported to enhance key fitness-relevant traits such as group coordination, multitasking and predator escape. Therefore, studies reporting negative effects on lateralization in fish due to environmental stressors such as ocean acidification, hypoxia and pollutants are worrisome. However, such studies tend to use a detour test and focus on population level measures, without validating whether lateralization is consistent within individuals across time. We conducted a multispecies, international assessment of the repeatability (R) of lateralization in four previously studied fish species using a detour test (T-maze), a common method for testing lateralization. We also reanalysed a published data set on a fifth species using new statistical methods. We expected the three shoaling species to exhibit greater within-individual consistency in lateralization than their nonshoaling counterparts given previous reports of stronger lateralization in group-living fishes. Absolute and relative lateralization scores were highly nonrepeatable in all five species (0.01<R<0.08), irrespective of their shoaling status. We carefully reviewed 31 published studies in which the detour test was employed to examine lateralization in fish and identified statistical issues in all of them. We develop and propose new statistical analyses to test for population and individual level lateralization. The commonly used detour test does not appear to be appropriate for quantifying behavioural lateralization in fishes, calling into question functional inferences drawn by many published studies, including our own. Potential fitness benefits of lateralization and anthropogenic effects on lateralization as a proxy for adaptive brain functioning need to be assessed with alternative paradigms.
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| 12. |
- Ros, Albert F. H., et al.
(författare)
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The impact of long-term reduced access to cleaner fish on health indicators of resident client fish
- 2020
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:24
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Tidskriftsartikel (refereegranskat)abstract
- In many mutualisms, benefits in the form of food are exchanged for services such as transport or protection. In the marine cleaning mutualism, a variety of 'client' reef fishes offer 'cleaner' fish Labroides dimidiatus access to food in the form of their ectoparasites, where parasite removal supposedly protects the clients. Yet, the health benefits individual clients obtain in the long term from repeated ectoparasite removal remain relatively unknown. Here, we tested whether long-term reduced access to cleaning services alters indicators of health status such as body condition, immunity and the steroids cortisol and testosterone in four client damselfish species Pomacentrus amboinensis, Amblyglyphidodon curacao, Acanthochromis polyacanthus and Dischistodus perspicillatus. To do so, we took advantage of a long-term experimental project in which several small reefs around Lizard Island (Great Barrier Reef, Australia) have been maintained cleaner-free since the year 2000, while control reefs had their cleaner presence continuously monitored. We found that the four damselfish species from reef sites without cleaners for 13 years had lower body condition than fish from reefs with cleaners. However, immunity measurements and cortisol and testosterone levels did not differ between experimental groups. Our findings suggest that clients use the energetic benefits derived from long-term access to cleaning services to selectively increase body condition, rather than altering hormonal or immune system functions.
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| 13. |
- Triki, Zegni, et al.
(författare)
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A proposal to enhance data quality and FAIRness
- 2022
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Ingår i: Ethology. - : Wiley. - 0179-1613 .- 1439-0310. ; 128:9, s. 647-651
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Forskningsöversikt (refereegranskat)abstract
- In recent years, we witnessed an increasing number of funding agencies, scientific journals and scientists agreeing that society and science benefit from open access to research data. Benefits derive mainly from increased access to knowledge for all and improved transparency and credibility in academia. However, despite the advances in open science and open data, three significant aspects still need considerable policing: data quality, the accompanying summaries with basic information of the data files (i.e. metadata) and computational codes used to generate the research outcomes. Only by having these three components together, we can achieve efficient data sharing and reuse, and hence higher transparency. Here, we present two complementary approaches that potentially can help with shared data quality: (i) data file(s) sharing should be guided step-by-step in public archives with mandatory metadata, and (ii) journals creating assistant data editor positions at editorial boards with a leading role in data quality and computational reproducibility. Forty-four editors-in-chief in the field of behaviour, ecology and evolution shared their opinion with us regarding these two approaches. Although most of the views were divided, the majority estimated that their current editorial board members do not have the necessary skills to assess the quality of shared data. Since data are the core of research studies, we should consider not only data presence but also quality as a requirement for publication.
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| 14. |
- Triki, Zegni, et al.
(författare)
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Brain morphology predicts social intelligence in wild cleaner fish
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The causes and consequences of social intelligence are challenging to establish. A study on wild cleaner fish reports that large forebrains enable individuals to score higher in a social competence test, suggesting forebrain size is important for complex social decision-making. It is generally agreed that variation in social and/or environmental complexity yields variation in selective pressures on brain anatomy, where more complex brains should yield increased intelligence. While these insights are based on many evolutionary studies, it remains unclear how ecology impacts brain plasticity and subsequently cognitive performance within a species. Here, we show that in wild cleaner fish (Labroides dimidiatus), forebrain size of high-performing individuals tested in an ephemeral reward task covaried positively with cleaner density, while cerebellum size covaried negatively with cleaner density. This unexpected relationship may be explained if we consider that performance in this task reflects the decision rules that individuals use in nature rather than learning abilities: cleaners with relatively larger forebrains used decision-rules that appeared to be locally optimal. Thus, social competence seems to be a suitable proxy of intelligence to understand individual differences under natural conditions.
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| 15. |
- Triki, Zegni, et al.
(författare)
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Marine Cleaning Mutualism Defies Standard Logic of Supply and Demand
- 2022
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 199:4, s. 455-467
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Tidskriftsartikel (refereegranskat)abstract
- Supply and demand affect the values of goods exchanged in cooperative trades. Studies of humans and other species typically describe the standard scenario that an increase in demand leads to a higher price. Here, we challenge the generality of that logic with empirical data and a theoretical model. In our study system, “client” fishes visit cleaner wrasse (Labroides dimidiatus) to have ectoparasites removed, but cleaners prefer client mucus, which constitutes “cheating.” We removed 31 of 65 preselected cleaners from a large isolated reef patch. We compared cleaner-client interactions at the reef and a control reef before removal and 4 weeks after removal. Cleaner fish from the experimental treatment site interacted more frequently with large clients (typically visitors with access to alternative cleaning stations), but we did not observe any changes in service quality measures. A game-theoretic analysis revealed that interaction duration and service quality might increase, decrease, or remain unchanged depending on the precise relationships between key parameters, such as the marginal benefits of cheating as a function of satiation or the likelihood of clients responding to cheating as a function of market conditions. The analyses show that the principle of diminishing return may affect exchanges in ways not predicted by supply-to-demand ratios.
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| 16. |
- Triki, Zegni, et al.
(författare)
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Relative Brain Size and Cognitive Equivalence in Fishes
- 2022
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Ingår i: Brain, behavior, and evolution. - : S. Karger AG. - 0006-8977 .- 1421-9743. ; 96:3, s. 124-136
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Tidskriftsartikel (refereegranskat)abstract
- Scientists have long struggled to establish how larger brains translate into higher cognitive performance across species. While absolute brain size often yields high predictive power of performance, its positive correlation with body size warrants some level of correction. It is expected that larger brains are needed to control larger bodies without any changes in cognitive performance. Potentially, the mean value of intraspecific brain-body slopes provides the best available estimate for an interspecific correction factor. For example, in primates, including humans, an increase in body size translates into an increase in brain size without changes in cognitive performance. Here, we provide the first evaluation of this hypothesis for another clade, teleost fishes. First, we obtained a mean intraspecific brain-body regression slope of 0.46 (albeit with a relatively large range of 0.26-0.79) from a dataset of 51 species, with at least 10 wild adult specimens per species. This mean intraspecific slope value (0.46) is similar to that of the encephalisation quotient reported for teleosts (0.5), which can be used to predict mean cognitive performance in fishes. Importantly, such a mean value (0.46) is much higher than in endothermic vertebrate species (<= 0.3). Second, we used wild-caught adult cleaner fish Labroides dimidiatus as a case study to test whether variation in individual cognitive performance can be explained by body size. We first obtained the brain-body regression slope for this species from two different datasets, which gave slope values of 0.58 (MRI scan data) and 0.47 (dissection data). Then, we used another dataset involving 69 adult cleaners different from those tested for their brain-body slope. We found that cognitive performance from four different tasks that estimated their learning, numerical, and inhibitory control abilities was not significantly associated with body size. These results suggest that the intraspecific brain-body slope captures cognitive equivalence for this species. That is, individuals that are on the brain-body regression line are cognitively equal. While rather preliminary, our results suggest that fish and mammalian brain organisations are fundamentally different, resulting in different intra- and interspecific slopes of cognitive equivalence.
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| 17. |
- Triki, Zegni, et al.
(författare)
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Sex differences in the cognitive abilities of a sex-changing fish species Labroides dimidiatus
- 2021
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- Males and females of the same species are known to differ at least in some cognitive domains, but such differences are not systematic across species. As a consequence, it remains unclear whether reported differences generally reflect adaptive adjustments to diverging selective pressures, or whether differences are mere side products of physiological differences necessary for reproduction. Here, we show that sex differences in cognition occur even in a sex-changing species, a protogynous hermaphroditic species where all males have previously been females. We tested male and female cleaner fish Labroides dimidiatus in four cognitive tasks to evaluate their learning and inhibitory control abilities first in an abstract presentation of the tasks, then in more ecologically relevant contexts. The results showed that males were better learners than females in the two learning tasks (i.e. reversal learning as an abstract task and a food quantity assessment task as an ecologically relevant task). Conversely, females showed enhanced abilities compared with males in the abstract inhibitory control task (i.e. detour task); but both sexes performed equally in the ecologically relevant inhibitory control task (i.e. 'audience effect' task). Hence, sex-changing species may offer unique opportunities to study proximate and/or ultimate causes underlying sex differences in cognitive abilities.
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| 18. |
- van Schaik, Carel P., et al.
(författare)
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A Farewell to the Encephalization Quotient : A New Brain Size Measure for Comparative Primate Cognition
- 2021
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Ingår i: Brain, behavior, and evolution. - : S. Karger AG. - 0006-8977 .- 1421-9743. ; 96:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Both absolute and relative brain sizes vary greatly among and within the major vertebrate lineages. Scientists have long debated how larger brains in primates and hominins translate into greater cognitive performance, and in particular how to control for the relationship between the noncognitive functions of the brain and body size. One solution to this problem is to establish the slope of cognitive equivalence, i.e., the line connecting organisms with an identical bauplan but different body sizes. The original approach to estimate this slope through intraspecific regressions was abandoned after it became clear that it generated slopes that were too low by an unknown margin due to estimation error. Here, we revisit this method. We control for the error problem by focusing on highly dimorphic primate species with large sample sizes and fitting a line through the mean values for adult females and males. We obtain the best estimate for the slope of circa 0.27, a value much lower than those constructed using all mammal species and close to the value expected based on the genetic correlation between brain size and body size. We also find that the estimate of cognitive brain size based on cognitive equivalence fits empirical cognitive studies better than the encephalization quotient, which should therefore be avoided in future studies on primates and presumably mammals and birds in general. The use of residuals from the line of cognitive equivalence may change conclusions concerning the cognitive abilities of extant and extinct primate species, including hominins.
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