The Development of Risk Preferences in Chimpanzees

• In Event: The Development of Risk Preferences and Exploration Strategies in Human Children and Chimpanzees

Abstract

Both human and nonhuman animals regularly make decisions involving risks. Depending on the discipline, the term “risk” can refer to danger, undesirable events, variance in food and monetary outcomes, or uncertainties. Responses to these properties of the environment are commonly referred to as “risk preferences” and are typically elicited through questionnaires (stated-preferences) or behavioral measures (revealed-preferences). Across disciplines, one important question concerns the development of risk preferences over the lifespan. Various theoretical and empirical accounts have proposed that in humans age and sex are especially robust predictors: risk preferences increase in adolescence and early adulthood (especially for men), followed by a decline across the adult lifespan (e.g. Dohmen et al., 2011; Mata et al., 2016) and men are generally more risk seeking than women (e.g. Frey et al., 2020). It remains an open question whether these patterns are uniquely human or shared with one of human’s closest living relatives. Chimpanzees and humans are highly genetically related, live in large, mixed sex social groups and have similar developmental stages with a long infant dependency, a period of adolescence and a long life expectancy of up to 50 years. Studying how one of our closest living relatives deal with risks will help us shed light on the evolutionary roots of human risk preferences and exploration strategies of different environments.
In the current project, we investigated the development of chimpanzees’ risk preferences across different measurements and domains. We applied a multimethod approach, adapting both a survey to measure risk preferences in social and nonsocial domains and an experiment to assess the willingness to explore risky and ambiguous environments. The total sample for the survey comprised 86 semi-free-ranging chimpanzees (46 females) from infancy to adulthood (age: M = 22.2 years ± 9.24 SD, range = 2 – 40) from Ngamba Island Chimpanzee Sanctuary in Uganda and Sweetwaters Chimpanzee Sanctuary in Kenya. Raters for the survey were caregivers (N = 17) at the sanctuaries who interacted with the chimpanzees on a daily basis. The experimental sample is a subsample of the survey sample and comprises 55 semi-free-ranging chimpanzees (31 females) from childhood to adulthood (age: M = 20.73 years ± 7.18 SD, range = 6 – 35) from both sanctuaries.
We investigated whether across measurements and domains (1) chimpanzees’ risk preferences increase in adolescence and early adulthood (especially for males), followed by a decline across the adult lifespan and whether (2) chimpanzee males are generally more risk prone than females. Over the life course, in most domains we find an inverted U-shape pattern, with a peak in young adulthood for males, and a flatter curve for females. Moreover, across measurements and domains male chimpanzees are generally more risk seeking than females. The results of the current study suggest that the development of human and chimpanzees’ risk preferences and exploration strategies follow similar trajectories. I will discuss advantages of the multimethod approach and possible implications of our findings.

Authors

• Lou M. Haux, Max Planck Institute for Human Development
  Presenting Author

• Jan Engelmann, University of California - Berkeley
  Non-Presenting Author

• Ruben Arslan, Max Planck Institute for Human Development
  Non-Presenting Author

• Ralph Hertwig, Max Planck Institute for Human Development
  Non-Presenting Author

• Esther Herrmann, University of Portsmouth
  Non-Presenting Author