Pontus Strimling

When natural selection favors imitation of parents

It is commonly assumed that parents are important sources of socially learned behavior and beliefs. However, the empirical evidence that parents are cultural models is ambiguous, and debates continue over their importance. A formal theory that examines the evolution of psychological tendencies to imitate parents (vertical transmission) and to imitate nonparent adults (oblique transmission) in stochastic fluctuating environments points to forces that sometimes make vertical transmission adaptive, but oblique transmission recovers more quickly from rapid environmental change. These results suggest that neither mode of transmission should be expected to dominate the other across all domains. Vertical transmission may be preferred when (1) learned behavior affects fertility rather than survival to adulthood, (2) the relevant environment is stable, or (3) selection is strong. For those interested in the evolution of social learning in diverse taxa, these models provide predictions for use in comparative studies.

Wild Chimpanzees Rely on Cultural Knowledge to Solve an Experimental Honey Acquisition Task

Population and group-specific behavioral differences have been taken as evidence for animal cultures, a notion that remains controversial. Skeptics argue that ecological or genetic factors, rather than social learning, provide a more parsimonious explanation. Work with captive chimpanzees has addressed this criticism by showing that experimentally created traditions can be transmitted through social learning. Recent fieldwork further suggests that ecological and genetic factors are insufficient to explain the behavioral differences seen between communities, but the data are only observational. Here, we present the results of a field experiment that compared the performance of chimpanzees (P. t. schweinfurthii) from two Ugandan communities, Kanyawara and Sonso, on an identical task in the physical domain-extracting honey from holes drilled into horizontal logs. Kanyawara chimpanzees, who occasionally use sticks to acquire honey, spontaneously manufactured sticks to extract the experimentally provided honey. In contrast, Sonso chimpanzees, who possess a considerable leaf technology but no food-related stick use, relied on their fingers, but some also produced leaf sponges to access the honey. Our results indicate that, when genetic and environmental factors are controlled, wild chimpanzees rely on their cultural knowledge to solve a novel task.

One cultural parent makes no culture

The ability to acquire knowledge and skills from others is widespread in animals and is commonly thought to be responsible for the behavioural traditions observed in many species. However, in spite of the extensive literature on theoretical analyses and empirical studies of social learning, little attention has been given to whether individuals acquire knowledge from a single individual or multiple models. Researchers commonly refer to instances of sons learning from fathers, or daughters from mothers, while theoreticians have constructed models of uniparental transmission, with little consideration of whether such restricted modes of transmission are actually feasible. We used mathematical models to demonstrate that the conditions under which learning from a single cultural parent can lead to stable culture are surprisingly restricted (the same reasoning applies to a single social-learning event). Conversely, we demonstrate how learning from more than one cultural parent can establish culture, and find that cultural traits will reach a nonzero equilibrium in the population provided the product of the fidelity of social learning and the number of cultural parents exceeds 1. We discuss the implications of the analysis for interpreting various findings in the animal social-learning literature, as well as the unique features of human culture.

THE EVOLUTION OF TEACHING

Teaching, alongside imitation, is widely thought to underlie the success of humanity by allowing high‐fidelity transmission of information, skills, and technology between individuals, facilitating both cumulative knowledge gain and normative culture. Yet, it remains a mystery why teaching should be widespread in human societies but extremely rare in other animals. We explore the evolution of teaching using simple genetic models in which a single tutor transmits adaptive information to a related pupil at a cost. Teaching is expected to evolve where its costs are outweighed by the inclusive fitness benefits that result from the tutors relatives being more likely to acquire the valuable information. We find that teaching is not favored where the pupil can easily acquire the information on its own, or through copying others, or for difficult to learn traits, where teachers typically do not possess the information to pass on to relatives. This leads to a narrow range of traits for which teaching would be efficacious, which helps to explain the rarity of teaching in nature, its unusual distribution, and its highly specific nature. Further models that allow for cumulative cultural knowledge gain suggest that teaching evolved in humans because cumulative culture renders otherwise difficult‐to‐acquire valuable information available to teach.

Three-dimensional stable matching with cyclic preferences

We consider stable three-dimensional matchings of three genders (3GSM). Alkan [Alkan, A., 1988. Non-existence of stable threesome matchings. Mathematical Social Sciences 16, 207–209] showed that not all instances of 3GSM allow stable matchings. Boros et al. [Boros, E., Gurvich, V., Jaslar, S., Krasner, D., 2004. Stable matchings in three-sided systems with cyclic preferences. Discrete Mathematics 286, 1–10] showed that if preferences are cyclic, and the number of agents is limited to three of each gender, then a stable matching always exists. Here we extend this result to four agents of each gender. We also show that a number of well-known sufficient conditions for stability do not apply to cyclic 3GSM. Based on computer search, we formulate a conjecture on stability of “strongest link” 3GSM, which would imply stability of cyclic 3GSM.

Optimal Expected Rank in a Two-Sided Secretary Problem

In a two-sided version of the famous secretary problem, employers search for a secretary at the same time as secretaries search for an employer. Nobody accepts being put on hold, and nobody is willing to take part in more than N interviews. Preferences are independent, and agents seek to optimize the expected rank of the partner they obtain among the N potential partners. We find that in any subgame perfect equilibrium, the expected rank grows as the square root of N (whereas it tends to a constant in the original secretary problem). We also compute how much agents can gain by cooperation.

How does opportunistic behavior influence firm size? An evolutionary approach to organizational behavior

This paper relates firm size and opportunism by showing that, given certain behavioural dispositions of humans, the size of a profit-maximizing firm can be determined by cognitive aspects underlying firm-internal cultural transmission processes. We argue that what firms do better than markets – besides economizing on transaction costs – is to establish a cooperative regime among its employees that keeps in check opportunism. A model depicts the outstanding role of the entrepreneur or business leader in firm-internal socialization processes and the evolution of corporate cultures. We show that high opportunism-related costs are a reason for keeping firms’ size small.