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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.
    Ghirlanda, Stefano
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Old and Young Individuals' Role in Cultural Change2012In: JASSS: Journal of Artificial Societies and Social Simulation, ISSN 1460-7425, E-ISSN 1460-7425, Vol. 15, no 4, article id 1Article in journal (Refereed)
    Abstract [en]

    We explore the impact of age on cultural change through simulations of cultural evolution. Our simulations show that common observations about the relationship between old and young naturally emerge from repeated cultural learning. In particular, young individuals are more open to learn than older individuals, they are less effective as cultural models, and they possess less cultural traits. We also show that, being more open to learning, young individuals are an important source of cultural change. Cultural change, however, is faster in populations with both young and old. A relatively large share of older individuals, in fact, allows a population to retain more culture, and a large culture can change in more directions than a small culture. For the same reason, considering age-biased cultural transmission in an overlapping generations model, cultural evolution is slower when individuals interact preferentially with models of similar age than when they mainly interact with older models.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 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.
    Botelho, Salome C.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Enquist, Karl
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Draheim, Roger R.
    Differential repositioning of the second transmembrane helices from E. coli Tar and EnvZ upon moving the flanking aromatic residues2015In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1848, no 2, p. 615-621Article in journal (Refereed)
    Abstract [en]

    Aromatic tuning, i.e. repositioning aromatic residues found at the cytoplasmic end of transmembrane (TM) domains within bacterial receptors, has been previously shown to modulate signal output from the aspartate chemoreceptor (Tar) and the major osmosensor EnvZ of Escherichia coli. In the case of Tar, changes in signal output consistent with the vertical position of the native Trp-Tyr aromatic tandem within TM2 were observed. In contrast, within EnvZ, where a Trp-Leu-Phe aromatic triplet was repositioned, the surface that the triplet resided upon was the major determinant governing signal output. However, these studies failed to determine whether moving the aromatic residues was sufficient to physically reposition the TM helix within a membrane. Recent coarse-grained molecular dynamics (CG-MD) simulations predicted displacement of Tar TM2 upon moving the aromatic residues at the cytoplasmic end of the helix. Here, we demonstrate that repositioning the Trp-Tyr tandem within Tar TM2 displaces the C-terminal boundary of the helix relative to the membrane. In a similar analysis of EnvZ, an abrupt initial displacement of TM2 was observed but no subsequent movement was seen, suggesting that the vertical position of TM2 is not governed by the location of the Trp-Leu-Phe triplet. Our results also provide another set of experimental data, i.e. the resistance of EnvZ TM2 to being displaced upon aromatic tuning, which could be useful for subsequent refinement of the initial CG-MD simulations. Finally, we discuss the limitations of these methodologies, how moving flanking aromatic residues might impact steady-state signal output and the potential to employ aromatic tuning in other bacterial membrane-spanning receptors.

  • 9.
    Enquist, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Fransson, Mawritz
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Boekel, Carolina
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bengtsson, Inger
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Geiger, Karin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lang, Lisa
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pettersson, Aron
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Johansson, Sofia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nilsson, IngMarie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Membrane-integration characteristics of two ABC transporters, CFTR and P-glycoprotein2009In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 387, no 5, p. 1153-1164Article in journal (Refereed)
    Abstract [en]

    To what extent do corresponding transmembrane helices in related integral membrane proteins have different membrane-insertion characteristics? Here, we compare, side-by-side, the membrane insertion characteristics of the 12 transmembrane helices in the adenosine triphosphate-binding cassette (ABC) transporters, P-glycoprotein (P-gp) and the cystic fibrosis transmembrane conductance regulator (CFTR). Our results show that 10 of the 12 CFTR transmembrane segments can insert independently into the ER membrane. In contrast, only three of the P-gp transmembrane segments are independently stable in the membrane, while the majority depend on the presence of neighboring loops and/or transmembrane segments for efficient insertion. Membrane-insertion characteristics can thus vary widely between related proteins.

  • 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.
    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.

  • 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.
    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)
  • 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. 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)
  • 13.
    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).

  • 14.
    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.

  • 15.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Hurd, Peter L.
    Ghirlanda, Stefano
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Signaling2010In: Evolutionary Behavioral Ecology / [ed] David F. Westneat, Charles W. Fox, Oxford: Oxford University Press, 2010, p. 266-284Chapter in book (Other academic)
  • 16.
    Enquist, Magnus
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Johan
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Världshistoria och kulturell evolution2010Other (Other academic)
  • 17.
    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.

  • 18.
    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)
  • 19.
    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)
  • 20.
    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)
  • 21.
    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)
  • 22.
    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)
  • 23.
    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.

  • 24.
    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.

  • 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.
    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)
  • 26.
    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).

  • 27.
    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.

  • 28.
    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.

  • 29.
    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)
  • 30.
    Hedin, Linnea E.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Öjemalm, Karin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bernsel, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hennerdal, Aron
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Illergård, Kristoffer
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Enquist, Karl
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Kauko, Anni
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lerch-Bader, Mirjam
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nilsson, IngMarie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Elofsson, Arne
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Membrane Insertion of Marginally Hydrophobic Transmembrane Helices Depends on Sequence Context2010In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 396, no 1, p. 221-229Article in journal (Refereed)
    Abstract [en]

    In mammalian cells, most integral membrane proteins are initially inserted into the endoplasmic reticulum membrane by the so-called Sec61 translocon. However, recent predictions suggest that many transmembrane helices (TMHs) in multispanning membrane proteins are not sufficiently hydrophobic to be recognized as such by the translocon. In this study, we have screened 16 marginally hydrophobic TMHs from membrane proteins of known three-dimensional structure. Indeed, most of these TMHs do not insert efficiently into the endoplasmic reticulum membrane by themselves. To test if loops or TMHs immediately upstream or downstream of a marginally hydrophobic helix might influence the insertion efficiency, insertion of marginally hydrophobic helices was also studied in the presence of their neighboring loops and helices. The results show that flanking loops and nearest-neighbor TMHs are sufficient to ensure the insertion of many marginally hydrophobic helices. However, for at least two of the marginally hydrophobic helices, the local interactions are not enough, indicating that post-insertional rearrangements are involved in the folding of these proteins.

  • 31.
    Isaksson, Sven
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory.
    Funcke, Alexander
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution. University of Pennsylvania, USA.
    Envall, Ida
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Lindenfors, Patrik
    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, Animal Ecology.
    A Novel Method to Analyze Social Transmission in Chronologically Sequenced Assemblages, Implemented on Cultural Inheritance of the Art of Cooking2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 5, article id e0122092Article in journal (Refereed)
    Abstract [en]

    Here we present an analytical technique for the measurement and evaluation of changes in chronologically sequenced assemblages. To illustrate the method, we studied the cultural evolution of European cooking as revealed in seven cook books dispersed over the past 800 years. We investigated if changes in the set of commonly used ingredients were mainly gradual or subject to fashion fluctuations. Applying our method to the data from the cook books revealed that overall, there is a clear continuity in cooking over the ages - cooking is knowledge that is passed down through generations, not something (re-) invented by each generation on its own. Looking at three main categories of ingredients separately (spices, animal products and vegetables), however, disclosed that all ingredients do not change according to the same pattern. While choice of animal products was very conservative, changing completely sequentially, changes in the choices of spices, but also of vegetables, were more unbounded. We hypothesize that this may be due a combination of fashion fluctuations and changes in availability due to contact with the Americas during our study time period. The presented method is also usable on other assemblage type data, and can thus be of utility for analyzing sequential archaeological data from the same area or other similarly organized material.

  • 32.
    Jansson, Liselotte
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Enquist, Magnus
    Testing the receiver bias hypothesis empirically with “virtual evolution”2005In: Animal Behaviour, ISSN 1095-8282, Vol. 70, no 4, p. 865-875Article in journal (Refereed)
    Abstract [en]

    Many signals found in nature seem exaggerated, for instance in size or colour. According to the receiver bias hypothesis such signal features evolve as a consequence of nonfunctional response biases in receivers. In this study we tested this hypothesis using chickens, Gallus gallus domesticus, in a virtual evolution experiment testing the potentiality of receiver bias to drive the evolution of exaggerated signals. The chickens played the role of receivers that can respond to the preferred stimuli displayed by the sender on a peck-sensitive computer screen. The preferred stimulus was kept and evolved, in the direction specified by the chicken, before being introduced to the next chicken of the successive generation. The chickens were tested on signals changing in three dimensions: length, intensity and area. In all three cases, the signals became considerably exaggerated and beyond what was required for accurate discrimination. Our results support the hypothesis that response biases emerging in discrimination tasks are sufficient to cause the evolution of signal exaggeration

  • 33.
    Jansson, Liselotte
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Forkman, Björn
    Department of Animal Science & Animal Health, Royal Veterinary and Agricultural University.
    Magnus, Enquist
    Stockholm University, Faculty of Science, Department of Zoology.
    Experimental evidence of receiver bias for symmetry2002In: Animal Behaviour, ISSN 0003-3472, Vol. 63, no 3, p. 617-621Article in journal (Refereed)
    Abstract [en]

    This experiment provides the first empirical evidence that symmetry preferences may arise as a by-product of animals' recognition mechanisms. We used a computer touch screen to train domestic fowl, Gallus gallus domesticus, to discriminate between rewarding and nonrewarding stimuli. The rewarding stimuli consisted of two slightly asymmetrical crosses that were mirror images of each other. After training, all subjects preferred a novel symmetrical cross to the asymmetrical training stimuli. Naïve hens tested on the same symbols but without any previous training did not show any symmetry preferences. These results show that symmetry preferences can emerge after experiences with different stimuli that are asymmetrical but that are symmetrical when combined. A preference for symmetrical signals may thus arise as a consequence of generalization and without any link to, for instance, quality of the signal sender

  • 34.
    Jansson, Liselotte
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Magnus, Enquist
    Receiver bias for colourful signals2003In: Animal Behaviour, ISSN 0003-3472, Vol. 66, no 5, p. 965-971Article in journal (Refereed)
    Abstract [en]

    Animals tend to respond more strongly to signals that are more colourful and such signals are also common in nature. This is the first study to explore experimentally the possibility that response biases arising in an animal's recognition mechanisms can explain these findings. We trained domestic fowls, Gallus gallus domesticus, to respond by pecking or not pecking to different colours displayed on a touch-sensitive computer screen. The colours changed in response to the birds' choices, which mimicked a simple evolutionary process. Discrimination training generated response biases for the colours more distinct from the nonrewarding colour. As a result the signals evolved towards distinct coloration. The biases developed in directions towards more intense and towards less intense colour, depending on the colour of the nonrewarding stimulus. The result may be applicable to all sorts of visual signals encountered during the same kind of experiences, that is, when one signal should be avoided and another should be approached

  • 35.
    Kolk, Martin
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Cownden, Daniel
    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.
    Correlations in fertility across generations: can low fertility persist?2014In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1779, p. 20132561-Article in journal (Refereed)
    Abstract [en]

    Correlations in family size across generations could have a major influence on human population size in the future. Empirical studies have shown that the associations between the fertility of parents and the fertility of children are substantial and growing over time. Despite their potential long-term consequences, intergenerational fertility correlations have largely been ignored by researchers. We present a model of the fertility transition as a cultural process acting on new lifestyles associated with fertility. Differences in parental and social influences on the acquisition of these lifestyles result in intergenerational correlations in fertility. We show different scenarios for future population size based on models that disregard intergenerational correlations in fertility, models with fertility correlations and a single lifestyle, and models with fertility correlations and multiple lifestyles. We show that intergenerational fertility correlations will result in an increase in fertility over time. However, present low-fertility levels may persist if the rapid introduction of new cultural lifestyles continues into the future.

  • 36.
    Lara, Patricia
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Tellgren-Roth, Åsa
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Behesti, Hourinaz
    Horn, Zachi
    Schiller, Nina
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Enquist, Karl
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Cammenberg, Malin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Liljenström, Amanda
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hatten, Mary E.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nilsson, IngMarie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Murine astrotactins 1 and 2 have a similar membrane topology and mature via endoproteolytic cleavage catalyzed by a signal peptidase2019In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 294, no 12, p. 4538-4545Article in journal (Refereed)
    Abstract [en]

    Astrotactin 1 (Astn1) and Astn2 are membrane proteins that function in glial-guided migration, receptor trafficking, and synaptic plasticity in the brain as well as in planar polarity pathways in the skin. Here we used glycosylation mapping and protease protection approaches to map the topologies of mouse Astn1 and Astn2 in rough microsomal membranes and found that Astn2 has a cleaved N-terminal signal peptide, an N-terminal domain located in the lumen of the rough microsomal membranes (topologically equivalent to the extracellular surface in cells), two transmembrane helices, and a large C-terminal lumenal domain. We also found that Astn1 has the same topology as Astn2, but we did not observe any evidence of signal peptide cleavage in Astn1. Both Astn1 and Astn2 mature through endoproteolytic cleavage in the second transmembrane helix; importantly, we identified the endoprotease responsible for the maturation of Astn1 and Astn2 as the endoplasmic reticulum signal peptidase. Differences in the degree of Astn1 and Astn2 maturation possibly contribute to the higher levels of the C-terminal domain of Astn1 detected on neuronal membranes of the central nervous system. These differences may also explain the distinct cellular functions of Astn1 and Astn2, such as in membrane adhesion, receptor trafficking, and planar polarity signaling.

  • 37.
    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.
    More synthetic work is needed2009In: Adaptive Behavior, ISSN 1059-7123, E-ISSN 1741-2633, Vol. 17, no 4, p. 329-330Article in journal (Refereed)
  • 38.
    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.

  • 39.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Enqvist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Insight Learning and Shaping.2012In: Encyclopedia of the Sciences of Learning, Springer Publishing Company, 2012, p. 1574-1577Chapter in book (Refereed)
  • 40.
    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)
  • 41.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Ghirlanda, Stefano
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Social learning through associative processes: a computational theory2019In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 6, no 3, article id 181777Article in journal (Refereed)
    Abstract [en]

    Social transmission of information is a key phenomenon in the evolution of behaviour and in the establishment of traditions and culture. The diversity of social learning phenomena has engendered a diverse terminology and numerous ideas about underlying learning mechanisms, at the same time that some researchers have called for a unitary analysis of social learning in terms of associative processes. Leveraging previous attempts and a recent computational formulation of associative learning, we analyse the following learning scenarios in some generality: learning responses to social stimuli, including learning to imitate; learning responses to non-social stimuli; learning sequences of actions; learning to avoid danger. We conceptualize social learning as situations in which stimuli that arise from other individuals have an important role in learning. This role is supported by genetic predispositions that either cause responses to social stimuli or enable social stimuli to reinforce specific responses. Simulations were performed using a new learning simulator program. The simulator is publicly available and can be used for further theoretical investigations and to guide empirical research of learning and behaviour. Our explorations show that, when guided by genetic predispositions, associative processes can give rise to a wide variety of social learning phenomena, such as stimulus and local enhancement, contextual imitation and simple production imitation, observational conditioning, and social and response facilitation. In addition, we clarify how associative mechanisms can result in transfer of information and behaviour from experienced to naive individuals.

  • 42.
    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.

  • 43.
    Lind, Johan
    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.
    Lönnberg, Sofie
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Centre for the Study of Cultural Evolution.
    Persson, Tomas
    Enquist, Magnus
    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.
    Time Does Not Help Orangutans Pongo abelii Solve Physical Problems2017In: Frontiers in Psychology, ISSN 1664-1078, E-ISSN 1664-1078, Vol. 8, article id 161Article in journal (Refereed)
    Abstract [en]

    Many questions in animal intelligence and cognition research are challenging. One challenge is to identify mechanisms underlying reasoning in experiments. Here, we provide a way to design such tests in non-human animals. We know from research in skill acquisition in humans that reasoning and thinking can take time because some problems are processed in multiple steps before a solution is reached (e.g., during mental arithmetics). If animals are able to learn through similar processes their decision making can be time consuming, and most importantly improve if more time to process information is allowed. We tested if performance of two Sumatran orangutans (Pongo abelii) increased in a two-choice experiment when they were allowed extra time before making their decisions, compared to when they were forced to decide immediately. We found that the performance of the orangutans did not depend on the time they were allowed to process the information before making their decisions. This methodology provides a potential avenue for empirical tests of mechanisms underlying reasoning in non-human animals.

  • 44.
    Lindenfors, Patrik
    et al.
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Envall, Ida
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Isaksson, Sven
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    An empirical study of cultural evolution: the development of European cookery from medieval to modern times2015In: Cliodynamics, ISSN 2373-7530, E-ISSN 2308-4294, Vol. 6, no 2, p. 115-129Article in journal (Refereed)
    Abstract [en]

    We have carried out an empirical study of long-term change in European cookery to test if the development of this cultural phenomenon matches a general hypothesis about cultural evolution: that human cultural change is characterized by cumulativity. Data from seven cookery books, evenly spaced across time, the oldest one written in medieval times (~1200) and the most recent one dating from late modernity (1999), were compared. Ten recipes from each of three categories (‘poultry recipes’, ‘fish recipes,’ and ‘meat recipes’) were arbitrarily selected from each cookery book by selecting the first ten recipes in each category, and the numbers (per recipe) of steps, separate partial processes, methods, ingredients, semi-manufactured ingredients, compound semi-manufactured ingredients (defined as semi-manufactured ingredients containing no less than two raw products), and self-made semi-manufactured ingredients were counted. Regression analyses were used to quantitatively compare the cookery from different ages. We found a significant increase in the numbers (per recipe) of steps, separate partial processes, methods, ingredients, and semi-manufactured ingredients. These significant increases enabled us to identify the development of cookery as an example of the general trend of cumulativity in long-term cultural evolution. The number of self-made semi-manufactured ingredients per recipe, however, tended to decrease over time, which may reflect the cumulative characteristics of cultural evolution at the level of society, considering the accumulation of knowledge that is required to industrialize food production.

  • 45.
    Lindenfors, Patrik
    et al.
    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.
    Enquist, Magnus
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Det unikt mänskliga2012In: Människans kunskap och kunskapen om människan: En gränslös historia / [ed] Maria Wallenberg Bondesson, Orsi Husz, Janken Myrdal, Mattias Tydén, Lund: Sekel Bokförlag, 2012, p. 31-44Chapter in book (Other academic)
  • 46.
    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.

  • 47. Rendell, L.
    et al.
    Boyd, R.
    Enquist, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Feldman, M. W.
    Fogarty, L.
    Laland, K. N.
    How copying affects the amount, evenness and persistence of cultural knowledge: insights from the social learning strategies tournament2011In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 366, no 1567, p. 1118-1128Article in journal (Refereed)
    Abstract [en]

    Darwinian processes should favour those individuals that deploy the most effective strategies for acquiring information about their environment. We organized a computer-based tournament to investigate which learning strategies would perform well in a changing environment. The most successful strategies relied almost exclusively on social learning (here, learning a behaviour performed by another individual) rather than asocial learning, even when environments were changing rapidly; moreover, successful strategies focused learning effort on periods of environmental change. Here, we use data from tournament simulations to examine how these strategies might affect cultural evolution, as reflected in the amount of culture (i.e. number of cultural traits) in the population, the distribution of cultural traits across individuals, and their persistence through time. We found that high levels of social learning are associated with a larger amount of more persistent knowledge, but a smaller amount of less persistent expressed behaviour, as well as more uneven distributions of behaviour, as individuals concentrated on exploiting a smaller subset of behaviour patterns. Increased rates of environmental change generated increases in the amount and evenness of behaviour. These observations suggest that copying confers on cultural populations an adaptive plasticity, allowing them to respond to changing environments rapidly by drawing on a wider knowledge base.

  • 48.
    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.

  • 49. Scorolli, C
    et al.
    Gihrlanda, S
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Enquist, M
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Etologi.
    Zattoni, S
    Jannini, E. A.
    Relative prevalence of different fetishes2007In: International Journal of Impotence Research, Vol. 19, no 4, p. 432-437Article in journal (Refereed)
  • 50. Sorjonen, Kimmo
    et al.
    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.
    Melin, Bo
    Male height and marital status2017In: Personality and Individual Differences, ISSN 0191-8869, E-ISSN 1873-3549, Vol. 104, p. 336-338Article in journal (Refereed)
    Abstract [en]

    Using conscription data and follow ups from a large representative sample of Swedish men, and in accordance with earlier studies, we found a bell shaped association between male height and the hazard-for not being unmarried. The shape of this association was not affected by indicators of health and socioeconomic status and it might, instead, be due to microeconomic factors such as supply and market value. A negative linear association between male height and the hazard for divorce once married was also found, and this association was accounted for by indicators of socioeconomic status.

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