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  • 1.
    Acerbi, Alberto
    et al.
    Department of Psychology, University of Bologna.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Department of Ethology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Cultural evolution and individual development of openness and conservatism2009In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, no 45, p. 18931-18935Article in journal (Refereed)
    Abstract [en]

    We present a model of cultural evolution in which an individual's propensity to engage in social learning is affected by social learning itself. We assume that individuals observe cultural traits displayed by others and decide whether to copy them based on their overall preference for the displayed traits. Preferences, too, can be transmitted between individuals. Our results show that such cultural dynamics tends to produce conservative individuals, i.e., individuals who are reluctant to copy new traits. Openness to new information, however, can be maintained when individuals need significant time to acquire the cultural traits that make them effective cultural models. We show that a gradual enculturation of young individuals by many models and a larger cultural repertoire to be acquired are favorable circumstances for the long-term maintenance of openness in individuals and groups. Our results agree with data about lifetime personality change, showing that openness to new information decreases with age. Our results show that cultural remodeling of cultural transmission is a powerful force in cultural evolution, i.e., that cultural evolution can change its own dynamics

  • 2.
    Acerbi, Alberto
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Regulatory traits: Cultural influences on cultural evolution2014In: Evolution, Complexity and Artificial Life / [ed] Stefano Cagnoni, Marco Mirolli, Marco Villani, Springer Berlin/Heidelberg, 2014, p. 135-147Chapter in book (Refereed)
    Abstract [en]

    We use the term regulatory traits to indicate traits that both regulate cultural transmission (e.g., from whom to learn) and are themselves culturally transmitted. In the first part of this contribution we study the dynamics of some of these traits through simple mathematical models. In particular, we consider the cultural evolution of traits that determine the propensity to copy others, the ability to influence others, the number of individuals from whom one may copy, and the number of individuals one tries to influence. We then show how to extend these simple models to address more complex human cultural phenomena, such as ingroup biases, the emergence of open or conservative societies, and of cyclical, fashion-like, increases and decreases of popularity of cultural traits. We finally discuss how the ubiquity of regulatory traits in cultural evolution impacts on the analogy between genetic and cultural evolution and therefore on the possibility of using models inspired by evolutionary biology to study human cultural dynamics.

  • 3.
    Acerbi, Alberto
    et al.
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Brooklyn College, US.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Regulatory Traits in Cultural Evolution2012In: Proceedings of WiVACE 2012, 2012, p. 1-9Conference paper (Refereed)
    Abstract [en]

    We call "regulatory traits" those cultural traits that are transmitted through cultural interactions and, at the same time, change individual behaviors directly influencing the outcome of future cultural interactions. The cultural dynamics of some of those traits are studied through simple simulations. In particular, we consider the cultural evolution of traits determining the propensity to copy, the number of potential demonstrators from whom one individual may copy, and conformist versus anti conformist attitudes. Our results show that regulatory traits generate peculiar dynamics that may explain complex human cultural phenomena. We discuss how the existence and importance of regulatory traits in cultural evolution impact on the analogy between genetic and cultural evolution and therefore on the possibility of using evolutionary biology inspired models to study human cultural dynamics.

  • 4.
    Acerbi, Alberto
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    The logic of fashion cycles2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 3, p. e32541-Article in journal (Refereed)
    Abstract [en]

    Many cultural traits exhibit volatile dynamics, commonly dubbed fashions or fads. Here we show that realistic fashion-like dynamics emerge spontaneously if individuals can copy others' preferences for cultural traits as well as traits themselves. We demonstrate this dynamics in simple mathematical models of the diffusion, and subsequent abandonment, of a single cultural trait which individuals may or may not prefer. We then simulate the coevolution between many cultural traits and the associated preferences, reproducing power-law frequency distributions of cultural traits (most traits are adopted by few individuals for a short time, and very few by many for a long time), as well as correlations between the rate of increase and the rate of decrease of traits (traits that increase rapidly in popularity are also abandoned quickly and vice versa). We also establish that alternative theories, that fashions result from individuals signaling their social status, or from individuals randomly copying each other, do not satisfactorily reproduce these empirical observations.

  • 5.
    Aguilar, Elliot
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. City University of New York, United States.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. City University of New York, United States; Brooklyn College, United States.
    Modeling the genealogy of a cultural trait2015In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 101, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The mathematical study of genealogies has yielded important insights in population biology, such as the ability to estimate the time to the most recent common ancestor (MRCA) of a sample of genetic sequences or of a group of individuals. Here we introduce a model of cultural genealogies that is a step toward answering similar questions for cultural traits. In our model individuals can inherit from a variable, potentially large number of ancestors, rather than from a fixed, small number of ancestors (one or two) as is typical of genetic evolution. We first show that, given a sample of individuals, a cultural common ancestor does not necessarily exist. We then introduce a related concept: the most recent unique ancestor (MRUA), i.e., the most recent single individual who is the earliest cultural ancestor of the sample. We show that, under neutral evolution, the time to the MRUA can be staggeringly larger than the time to MRCA in a single ancestor model, except when the average number of learning opportunities per individuals is small. Our results point out that the properties of cultural genealogies may be very different from those of genetic genealogies, with potential implications for reconstructing the histories of cultural traits.

  • 6.
    Aronsson, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Parental effects on sexual preferences in humans: A web study of attraction to glassesManuscript (preprint) (Other academic)
  • 7.
    Aronsson, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Lind, Johan
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Parental influences on sexual preferences: The case of attraction to smoking2011In: Journal of Evolutionary Psychology, ISSN 0737-4828, Vol. 9, no 1, p. 21-41Article in journal (Refereed)
    Abstract [en]

    We investigated whether a sexual preference for smoking can be related to past experiences of parental smoking during childhood, as predicted by the theory of sexual imprinting, but also by sexual conditioning theory. In a sample of over 4000 respondents to five Internet surveys on sexual preferences, we found that parental smoking correlates with increased attraction to smoking in self-reported hetero- and homosexual males. Maternal smoking was associated with an increase in attraction to smoking both in hetero- and homosexual males, while paternal smoking was associated with an increase in attraction to smoking only in males who prefer male partners. We could not explain these findings by considering other factors than parental smoking habits, such as possibly biased reporting, indicators of a sexually liberal lifestyle or phenotype matching. Our data are consistent with the hypothesis that sexual preferences are acquired early in life by exposure to stimuli provided by individuals in the child’s environment, such as caregivers. The sex specificity of the parental effect is consistent with sexual imprinting theory but not with conditioning theory.

  • 8.
    Contucci, Pierluigi
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Modeling society with statistical mechanics: an application to cultural contact and immigration2007In: Quality & Quantity, Vol. 41, p. 569-578Article in journal (Refereed)
  • 9.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Aronsson, Hanna
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Jansson, Liselott
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Jannini, Emmanuele A.
    Exposure to Mother's Pregnancy and Lactation in Infancy is Associated with Sexual Attraction to Pregnancy and Lactation in Adulthood2011In: Journal of Sexual Medicine, ISSN 1743-6095, E-ISSN 1743-6109, Vol. 8, no 1, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Introduction.  Several theories, including psychodynamic theories, sexual imprinting and early conditioning have been formulated to explain sexual development. Empirical data, however, remain insufficient for a thorough evaluation of these theories.

    Aim.  In this study, we test the hypothesis that a critical period exists for the acquisition of sexual preferences, as suggested by empirical findings in birds and mammals (sexual imprinting).

    Methods.  An Internet questionnaire was used.

    Main Outcome Measures.  We gather data from individuals with a sexual preference for pregnant and/or lactating women, under the hypothesis that pregnancy or lactation may become sexually attractive in adulthood following an exposure to pregnant or lactating women in infancy.

    Results.  We find that these preferences are more common in older siblings, i.e., in individuals who have been exposed to more maternal pregnancy and lactation. This result is independent of respondent and sibling sex. In addition, only maternal pregnancies and lactations experienced between 1.5 and 5 years of age are associated with the preferences.

    Conclusions.  We discuss our findings in relation to theories of sexual development and to earlier reports of birth order effects on sexual behavior. We suggest that this age range may constitute a sensitive period for the acquisition of sexual preferences.

  • 10.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Eriksson, Kimmo
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Critical social learning: a solution to Rogers paradox of non-adaptive culture2007In: American Anthropologist, Vol. 109, p. 727-734Article in journal (Refereed)
  • 11.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Evolution of social learning does not explain the origin of human cumulative culture2007In: Journal of Theoretical Biology, Vol. 246, no 1, p. 129-135Article in journal (Refereed)
  • 12.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Eriksson, Kimmo
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Modelling the evolution and diversity of cumulative culture2011In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 366, no 1563, p. 412-423Article in journal (Refereed)
    Abstract [en]

    Previous work on mathematical models of cultural evolution has mainly focused on the diffusion of simple cultural elements. However, a characteristic feature of human cultural evolution is the seemingly limitless appearance of new and increasingly complex cultural elements. Here, we develop a general modelling framework to study such cumulative processes, in which we assume that the appearance and disappearance of cultural elements are stochastic events that depend on the current state of culture. Five scenarios are explored: evolution of independent cultural elements, stepwise modification of elements, differentiation or combination of elements and systems of cultural elements. As one application of our framework, we study the evolution of cultural diversity (in time as well as between groups).

  • 13.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Jarrick, Arne
    Stockholm University, Faculty of Humanities, Department of History. Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Wachtmeister, C-A
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Why does human culture increase exponentially?2008In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 74, no 1, p. 46-55Article in journal (Refereed)
    Abstract [en]

    Historical records show that culture can increase exponentially in time, e.g., in number of poems, musical works, scientific discoveries. We model how human capacities for creativity and cultural transmission may make such an increase possible, suggesting that: (1) creativity played a major role at the origin of human culture and for its accumulation throughout history, because cultural transmission cannot, on its own, generate exponentially increasing amounts of culture; (2) exponential increase in amount of culture can only occur if creativity is positively influenced by culture. The evolution of cultural transmission is often considered the main genetic bottleneck for the origin of culture, because natural selection cannot favor cultural transmission without any culture to transmit. Our models suggest that an increase in individual creativity may have been the first step toward human culture, because in a population of creative individuals there may be enough non-genetic information to favor the evolution of cultural transmission.

  • 14.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. Brooklyn College, USA; Graduate Center of the City University of New York, USA.
    The power of associative learning and the ontogeny of optimal behaviour2016In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 3, no 11, article id 160734Article in journal (Refereed)
    Abstract [en]

    Behaving efficiently (optimally or near-optimally) is central to animals' adaptation to their environment. Much evolutionary biology assumes, implicitly or explicitly, that optimal behavioural strategies are genetically inherited, yet the behaviour of many animals depends crucially on learning. The question of how learning contributes to optimal behaviour is largely open. Here we propose an associative learning model that can learn optimal behaviour in a wide variety of ecologically relevant circumstances. The model learns through chaining, a term introduced by Skinner to indicate learning of behaviour sequences by linking together shorter sequences or single behaviours. Our model formalizes the concept of conditioned reinforcement (the learning process that underlies chaining) and is closely related to optimization algorithms from machine learning. Our analysis dispels the common belief that associative learning is too limited to produce ‘intelligent’ behaviour such as tool use, social learning, self-control or expectations of the future. Furthermore, the model readily accounts for both instinctual and learned aspects of behaviour, clarifying how genetic evolution and individual learning complement each other, and bridging a long-standing divide between ethology and psychology. We conclude that associative learning, supported by genetic predispositions and including the oft-neglected phenomenon of conditioned reinforcement, may suffice to explain the ontogeny of optimal behaviour in most, if not all, non-human animals. Our results establish associative learning as a more powerful optimizing mechanism than acknowledged by current opinion.

  • 15.
    Eriksson, Kimmo
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Critical points in current theory of conformist social learning2007In: Journal of Evolutionary Psychology, Vol. 5, p. 67-87Article in journal (Refereed)
  • 16.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. Brooklyn College, USA; CUNY Graduate Center, USA.
    Can squirrel monkeys learn an AB(n)A grammar? A re-evaluation of Ravignani et al. (2013)2017In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 5, article id e3806Article in journal (Refereed)
    Abstract [en]

    Ravignani et al (2013) abituated squirrel monkeys to sound sequences conforming to an ABnA grammar (n = 1, 2, 3), then tested them for their reactions to novel grammatical and non -grammatical sequences. Although they conclude that the monkeys consistently recognized and generalized the sequence AB(n)A, I remark that this conclusion is not robust. The statistical significance of results depends on specific choices of data analysis, namely dichotomization of the response variable and omission of specific data points. Additionally, there is little evidence of generalization to novel patterns (n = 4, 5), which is important to conclude that the monkeys recognized the AB(n)A grammar beyond the habituation patterns. Lastly, many test sequences were perceptually similar to habituation sequences, raising the possibility that the monkeys may have generalized based on perceptual similarity rather than based on grammaticality.

  • 17.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution. City University of New York, United States.
    Studying associative learning without solving learning equations2018In: Journal of mathematical psychology (Print), ISSN 0022-2496, E-ISSN 1096-0880, Vol. 85, p. 55-61Article in journal (Refereed)
    Abstract [en]

    I introduce a simple mathematical method to calculate the associative strengths of stimuli in many models of associative learning, without solving the models' learning equations and without simulating the learning process. The method applies to many models, including the Rescorla and Wagner (1972) model, the replaced elements model of Brandon et al. (2000), and Pearce's (1987) configural model. I illustrate the method by calculating the predictions of these three models in summation and blocking experiments, allowing for a degree of similarity between the training stimuli as well as for the effects of contextual stimuli. The method clarifies the models' predictions and suggests new empirical tests.

  • 18.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Acerbi, Alberto
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Nakamaru, Mayuko
    Department of Value and Decision Science, Tokyo Institute of Technology.
    The Sometimes Evitable Route to Conservatism and Persuasiveness: A Reply to Xue and Costopoulos2010In: Current Anthropology, ISSN 0011-3204, E-ISSN 1537-5382, Vol. 51, no 2, p. 271-272Article in journal (Refereed)
  • 19.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. City University of New York (CUNY), USA.
    Acerbi, Alberto
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. University of Bristol, England.
    Herzog, Harold
    Dog Movie Stars and Dog Breed Popularity: A Case Study in Media Influence on Choice2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 9, p. e106565-Article in journal (Refereed)
    Abstract [en]

    Fashions and fads are important phenomena that influence many individual choices. They are ubiquitous in human societies, and have recently been used as a source of data to test models of cultural dynamics. Although a few statistical regularities have been observed in fashion cycles, their empirical characterization is still incomplete. Here we consider the impact of mass media on popular culture, showing that the release of movies featuring dogs is often associated with an increase in the popularity of featured breeds, for up to 10 years after movie release. We also find that a movie's impact on breed popularity correlates with the estimated number of viewers during the movie's opening weekend-a proxy of the movie's reach among the general public. Movies' influence on breed popularity was strongest in the early 20th century, and has declined since. We reach these conclusions through a new, widely applicable method to measure the cultural impact of events, capable of disentangling the event's effect from ongoing cultural trends.

  • 20.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, NY, USA.
    Acerbi, Alberto
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. University of Bristol, England.
    Herzog, Harold
    Serpell, James A.
    Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 9, p. e74770-Article in journal (Refereed)
    Abstract [en]

    We investigate the relationship between characteristics of dog breeds and their popularity between years 1926 and 2005. We consider breed health, longevity, and behavioral qualities such as aggressiveness, trainability, and fearfulness. We show that a breed's overall popularity, fluctuations in popularity, and rates of increase and decrease around popularity peaks show typically no correlation with these breed characteristics. One exception is the finding that more popular breeds tend to suffer from more inherited disorders. Our results support the hypothesis that dog breed popularity has been primarily determined by fashion rather than function.

  • 21.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Cumulative culture and explosive demographic transitions2007In: Quality & Quantity, Vol. 41, no 4, p. 591-600Article in journal (Refereed)
  • 22.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    How training and testing histories affect generalisation: a test of simple neural networks2010In: Modelling Perception with Artificial Neural Networks / [ed] Colin R. Tosh, Graeme D. Ruxton, Cambridge: Cambridge University Press, 2010, p. 295-307Chapter in book (Refereed)
  • 23.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Etologi.
    How training and testing histories affect generalization: a test of simple neural networks2007In: Philosophical Transactions of The Royal Society B-Biological Sciences, Vol. 362, p. 449-454Article in journal (Refereed)
  • 24.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution. Brooklyn College, USA; City University of New York Graduate Center, USA.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution.
    On the Role of Responses in Pavlovian Acquisition2019In: Journal of experimental psychology: Animal learning and cognition, ISSN 2329-8456, Vol. 45, no 1, p. 59-74Article in journal (Refereed)
    Abstract [en]

    A defining feature of Pavlovian conditioning is that the unconditioned stimulus (US) is delivered whether or not the animal performs a conditioned response (CR). This has lead to the question: Does CR performance play any role in conditioning? Between the 1930s and 1970s. a consensus emerged that CR acquisition is driven by CS-US (CS, conditioned stimulus) experiences, and that CRs play a minimal role, if any. Here we revisit the question and present 2 new quantitative methods to evaluate whether CRs influence the course of learning. Our results suggest that CRs play an important role in Pavlovian acquisition, in such paradigms as rabbit eye blink conditioning, pigeon autoshaped key pecking, and rat autoshaped lever pressing and magazine entry.

  • 25.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Coevolution of intelligence, behavioral repertoire, and lifespan2014In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 91, p. 44-49Article in journal (Refereed)
    Abstract [en]

    Across many taxa, intriguing positive correlations exist between intelligence (measured by proxy as encephalization), behavioral repertoire size, and lifespan. Here we argue, through a simple theoretical model, that such correlations arise from selection pressures for efficient learning of behavior sequences. We define intelligence operationally as the ability to disregard unrewarding behavior sequences, without trying them out, in the search for rewarding sequences. We show that increasing a species' behavioral repertoire increases the number of rewarding behavior sequences that can be performed, but also the time required to learn such sequences. This trade-off results in an optimal repertoire size that decreases rapidly with increasing sequence length. Behavioral repertoire size can be increased by increasing intelligence or lengthening the lifespan, giving rise to the observed correlations between these traits.

  • 26.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Corrigendum to "Coevolution of intelligence, behavioral repertoire, and lifespan" [Theoret. Popul. Biol. 91 (2014) 44–49]2014In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 97, p. 57-57Article in journal (Other academic)
  • 27.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Perc, Matjaz
    Physics Department, University of Maribor, Slovenia.
    Sustainability of culture-driven population dynamics2010In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 77, no 3, p. 181-188Article in journal (Refereed)
    Abstract [en]

    We consider models of the interactions between human population dynamics and cultural evolution, asking whether they predict sustainable or unsustainable patterns of growth. Phenomenological models predict either unsustainable population growth or stabilization in the near future. The latter prediction, however, is based on extrapolation of current demographic trends and does not take into account causal processes of demographic and cultural dynamics. Most existing causal models assume (or derive from simplified models of the economy) a positive feedback between cultural evolution and demographic growth, and predict unlimited growth in both culture and population. We augment these models taking into account that: (1) cultural transmission is not perfect, i.e., culture can be lost; (2) culture does not always promote population growth. We show that taking these factors into account can cause radically different model behavior, such as population extinction rather than stability, and extinction rather than growth. We conclude that all models agree that a population capable of maintaining a large amount of culture, including a powerful technology, runs a high risk of being unsustainable. We suggest that future work must address more explicitly both the dynamics of resource consumption and the cultural evolution of beliefs implicated in reproductive behavior (e.g., ideas about the preferred family size) and in resource use (e.g., environmentalist stances).

  • 28.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Frasnelli, Elisa
    Vallortigara, Giorgio
    Intraspecific competition and coordination in the evolution of lateralization2009In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 364, no 1519, p. 861-866Article in journal (Refereed)
    Abstract [en]

    Recent studies have revealed a variety of left-right asymmetries among vertebrates and invertebrates. In many species, left-and right-lateralized individuals coexist, but in unequal numbers ('populationlevel' lateralization). It has been argued that brain lateralization increases individual efficiency (e. g. avoiding unnecessary duplication of neural circuitry and reducing interference between functions), thus counteracting the ecological disadvantages of lateral biases in behaviour (making individual behaviour more predictable to other organisms). However, individual efficiency does not require a definite proportion of left-and right-lateralized individuals. Thus, such arguments do not explain population-level lateralization. We have previously shown that, in the context of prey-predator interactions, population-level lateralization can arise as an evolutionarily stable strategy when individually asymmetrical organisms must coordinate their behaviour with that of other asymmetrical organisms. Here, we extend our model showing that populations consisting of left-and right-lateralized individuals in unequal numbers can be evolutionarily stable, based solely on strategic factors arising from the balance between antagonistic (competitive) and synergistic (cooperative) interactions.

  • 29.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. City University of New York.
    Ibadullayev, Ismet
    Solution of the comparator theory of associative learning2015In: Psychological review, ISSN 0033-295X, E-ISSN 1939-1471, Vol. 122, no 2, p. 242-259Article in journal (Refereed)
    Abstract [en]

    We derive an analytical solution of the comparator theory of associative learning, as formalized by Stout and Miller (2007). The solution enables us to calculate exactly the predicted responding to stimuli in any experimental design and for any choice of model parameters. We illustrate its utility by calculating the predictions of comparator theory in some paradigmatic designs: acquisition of conditioned responses, compound conditioning, blocking, unovershadowing, and backward blocking. We consider several versions of the theory: first-order comparator theory (close to the original ideas of Miller & Matzel, 1988), second-order comparator theory (Denniston, Savastano, & Miller, 2001), and sometimescompeting retrieval (Stout & Miller, 2007). We show that all versions of comparator theory make a number of surprising predictions, some of which appear hard to reconcile with empirical data. Our solution paves the way for a fuller understanding of the theory and for its empirical evaluation

  • 30.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jansson, Liselotte
    Stockholm University, Faculty of Science, Department of Zoology.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Chickens prefer beautiful humans2002In: Human Nature, ISSN 1936-4776, Vol. 13, no 3, p. 383-389Article in journal (Refereed)
    Abstract [en]

    We trained chickens to react to an average human female face but not to an average male face (or vice versa). In a subsequent test, the animals showed preferences for faces consistent with human sexual preferences (obtained from university students). This suggests that human preferences arise from general properties of nervous systems, rather than from face-specific adaptations. We discuss this result in the light of current debate on the meaning of sexual signals and suggest further tests of existing hypotheses about the origin of sexual preferences.

  • 31.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA; CUNY Graduate Center, USA.
    Lind, Johan
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    ‘Aesop's fable’ experiments demonstrate trial-and-error learning in birds, but no causal understanding2017In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 123, p. 239-247Article in journal (Refereed)
    Abstract [en]

    Experiments inspired by Aesop's fable The crow and the pitcher have been suggested to show that some birds (rooks, Corvus frugilegus, New Caledonian crows, Corvus moneduloides, and Eurasian jays, Garrulus glandarius) understand cause–effect relationships pertaining to water displacement. For example, the birds may prefer to drop stones in water rather than in sand in order to retrieve a floating food morsel, suggesting that they understand that only the level of water can be so raised. Here we re-evaluate the evidence for causal understanding in all published experiments (23 928 choices by 36 individuals). We first show that commonly employed statistical methods cannot disentangle the birds' initial performance on a task (which is taken as an indicator of causal understanding) from trial-and-error learning that may occur during the course of the experiment. We overcome this shortcoming with a new statistical analysis that quantifies initial performance and learning effects separately. We present robust evidence of trial-and-error learning in many tasks, and of an initial preference in a few. We also show that both seeming demonstrations of causal understanding and of lack of it can be understood based on established properties of instrumental learning. We conclude that Aesop's fable experiments have not yet produced evidence of causal understanding, and we suggest how the experimental designs can be modified to yield better tests of causal cognition.

  • 32.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. Brooklyn College, USA; Graduate Center of the City University of New York, USA.
    Lind, Johan
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Memory for stimulus sequences: a divide between humans and other animals?2017In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 6, article id 161011Article in journal (Refereed)
    Abstract [en]

    Humans stand out among animals for their unique capacities in domains such as language, culture and imitation, yet it has been difficult to identify cognitive elements that are specifically human. Most research has focused on how information is processed after it is acquired, e.g. in problem solving or 'insight' tasks, but we may also look for species differences in the initial acquisition and coding of information. Here, we show that non-human species have only a limited capacity to discriminate ordered sequences of stimuli. Collating data from 108 experiments on stimulus sequence discrimination (1540 data points from 14 bird and mammal species), we demonstrate pervasive and systematic errors, such as confusing a red-green sequence of lights with green-red and green-green sequences. These errors can persist after thousands of learning trials in tasks that humans learn to near perfection within tens of trials. To elucidate the causes of such poor performance, we formulate and test a mathematical model of non-human sequence discrimination, assuming that animals represent sequences as unstructured collections of memory traces. This representation carries only approximate information about stimulus duration, recency, order and frequency, yet our model predicts non-human performance with a 5.9% mean absolute error across 68 datasets. Because human-level cognition requires more accurate encoding of sequential information than afforded by memory traces, we conclude that improved coding of sequential information is a key cognitive element that may set humans apart from other animals.

  • 33.
    Ghirlanda, Stefano
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Magnus, Enquist
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Nakamaru, Mayuko
    Department of Systems Engineering, Shizuoka University.
    Cultural Evolution Develops Its Own Rules: The Rise of Conservatism and Persuasion2006In: Current Anthropology, ISSN 0011-3204, E-ISSN 1537-5382, Vol. 47, no 6, p. 1027-1034Article in journal (Refereed)
  • 34.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA.
    Animal memory: A review of delayed matching-to-sample data2015In: Behaviour Analysis Letters, ISSN 0376-6357, Vol. 117, p. 52-58Article, review/survey (Refereed)
    Abstract [en]

    We performed a meta-analysis of over 90 data sets from delayed matching-to-sample (DMTS) studies with 25 species (birds, mammals, and bees). In DMTS, a sample stimulus is first presented and then removed. After a delay, two (or more) comparison stimuli are presented, and the subject is rewarded for choosing the one matching the sample. We used data on performance vs. delay length to estimate two parameters informative of working memory abilities: the maximum performance possible with no delay (comparison stimuli presented as soon as the sample is removed), and the rate of performance decay as the delay is lengthened (related to memory span). We conclude that there is little evidence that zero-delay performance varies between these species. There is evidence that pigeons do not perform as well as mammals at longer delay intervals. Pigeons, however, are the only extensively studied bird, and we cannot exclude that other birds may be able to bridge as long a delay as mammals. Extensive training may improve memory, although the data are open to other interpretations. Overall, DMTS studies suggest memory spans ranging from a few seconds to several minutes. We suggest that observations of animals exhibiting much longer memory spans (days to months) can be explained in terms of specialized memory systems that deal with specific, biologically significant information, such as food caches. Events that do not trigger these systems, on the other hand, appear to be remembered for only a short time. This article is part of a Special Issue entitled: In Honor of jeriy Hogan.

  • 35.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Insight learning or shaping?2009In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, no 28, p. E76-Article in journal (Refereed)
  • 36.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Lindenfors, Patrik
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Brooklyn College, USA.
    Lidén, Kerstin
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Dating human cultural capacity using phylogenetic principles2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, article id 1785Article in journal (Refereed)
    Abstract [en]

    Humans have genetically based unique abilities making complex culture possible; an assemblage of traits which we term cultural capacity. The age of this capacity has for long been subject to controversy. We apply phylogenetic principles to date this capacity, integrating evidence from archaeology, genetics, paleoanthropology, and linguistics. We show that cultural capacity is older than the first split in the modern human lineage, and at least 170,000 years old, based on data on hyoid bone morphology, FOXP2 alleles, agreement between genetic and language trees, fire use, burials, and the early appearance of tools comparable to those of modern hunter-gatherers. We cannot exclude that Neanderthals had cultural capacity some 500,000 years ago. A capacity for complex culture, therefore, must have existed before complex culture itself. It may even originated long before. This seeming paradox is resolved by theoretical models suggesting that cultural evolution is exceedingly slow in its initial stages.

  • 37.
    Rendell, L
    et al.
    University of St. Andrews.
    Boyd, R
    University of California, Los Angeles,.
    Cownden, D
    Queen's University, Jeffery Hall, University Avenue, Kingston, Ontario.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Eriksson, Kimmo
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Feldman, W.M
    Stanford University, Stanford.
    Fogerty, L
    University of St. Andrews.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Lillicrap, T
    Queen's University, Jeffery Hall, University Avenue, Kingston, Ontario.
    Lalland, K
    University of St. Andrews.
    Why Copy Others?: Insights from theSocial Learning Strategies Tournament2010In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 328, no 5975, p. 208-213Article in journal (Refereed)
    Abstract [en]

    Social learning (learning through observation or interaction with other individuals) is widespread in nature and is central to the remarkable success of humanity, yet it remains unclear why copying is profitable and how to copy most effectively. To address these questions, we organized a computer tournament in which entrants submitted strategies specifying how to use social learning and its asocial alternative (for example, trial-and-error learning) to acquire adaptive behavior in a complex environment. Most current theory predicts the emergence of mixed strategies that rely on some combination of the two types of learning. In the tournament, however, strategies that relied heavily on social learning were found to be remarkably successful, even when asocial information was no more costly than social information. Social learning proved advantageous because individuals frequently demonstrated the highest-payoff behavior in their repertoire, inadvertently filtering information for copiers. The winning strategy (discountmachine) relied nearly exclusively on social learning and weighted information according to the time since acquisition.

  • 38.
    Scorolli, C
    et al.
    Department of Psychology, University of Bologna, Italy.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Department of Ethology.
    Jannini, E A
    Department of Experimental Medicine, L'Aquila University, L'Aquila, Italy.
    Relative prevalence of different fetishes2007In: International journal of impotence research, ISSN 0955-9930, E-ISSN 1476-5489, Vol. 19, p. 432-437Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to estimate the relative frequency of Fetishes in a large sample of individuals. Using the Internet as a data source, we examined 381 discussion groups. We estimate, very conservatively, that at least 5000 individuals were targeted. The relative frequency of each preference category was estimated considering (a) the number of groups devoted to the category, (b) the number of individuals participating in the groups and (c) the number of messages exchanged. The three measures agree both parametrically (Cronbach's =0.91) and non-parametrically (Kendall's W=0.94, P<0.01). Preferences for body parts or features and for objects usually associated with the body were most common (33 and 30%, respectively), followed by preferences for other people's behavior (18%), own behavior (7%), social behavior (7%) and objects unrelated to the body (5%). Feet and objects associated with feet were the most common target of preferences. These findings provide the first large database in an area, where the knowledge is particularly scarce.

  • 39. Yang, Yanpeng
    et al.
    Clément, Romain J. G.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution. Brooklyn College, United States; The Graduate Center of the City University of New York (CUNY), United States.
    Porfiri, Maurizio
    A Comparison of Individual Learning and Social Learning in Zebra fish Through an Ethorobotics Approach2019In: Frontiers in Robotics and AI, E-ISSN 2296-9144, Vol. 6, article id 71Article in journal (Refereed)
    Abstract [en]

    Social learning is ubiquitous across the animal kingdom, where animals learn from group members about predators, foraging strategies, and so on. Despite its prevalence and adaptive benefits, our understanding of social learning is far from complete. Here, we study observational learning in zebra fish, a popular animal model in neuroscience. Toward fine control of experimental variables and high consistency across trials, we developed a novel robotics-based experimental test paradigm, in which a robotic replica demonstrated to live subjects the correct door to join a group of conspecifics. We performed two experimental conditions. In the individual training condition, subjects learned the correct door without the replica. In the social training condition, subjects observed the replica approaching both the incorrect door, to no effect, and the correct door, which would open after spending enough time close to it. During these observations, subjects could not actively follow the replica. Zebra fish increased their preference for the correct door over the course of 20 training sessions, but we failed to identify evidence of social learning, whereby we did not register significant differences in performance between the individual and social training conditions. These results suggest that zebra fish may not be able to learn a route by observation, although more research comparing robots to live demonstrators is needed to substantiate this claim.

  • 40. Young, Briana
    et al.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Brooklyn College, USA.
    Grasso, Frank W.
    Parallel Implementation of Instinctual and Learning Neural Mechanisms in a Simulated Mobile Robot2012In: Biomimetic and Biohybrid Systems: Living machines / [ed] Tony J. Prescott, Nathan F. Lepora, Anna Mura, Paul F. M. J. Verschure, Springer, 2012, p. 298-308Conference paper (Refereed)
    Abstract [en]

    The question of how biological learning and instinctive neural mechanisms interact with each other in the course of development to produce novel, adaptive behaviors was explored via a robotic simulation. Instinctive behavior in the agent was implemented in a hard-wired network which produced obstacle avoidance. Phototactic behavior was produced in two serially connected plastic layers. A self-organizing feature map was combined with a reinforcement learning layer to produce a learning network. The reinforcement came from an internally generated signal. Both the adaptive and fixed networks supplied motor control signals to the robot motors. The sizes of the self-organizing layer, reinforcement layer, and the complexity of the environment were varied and effects on robot phototactic efficiency and accuracy in the mature networks were measured. A significant interaction of the three independent variables was found, supporting the idea that organisms evolve distinct combinations of instinctive and plastic neural mechanisms which are tailored to the demands of the environment in which their species evolved.

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