Understanding Natural Selection is Associated With Decreased Essentialist Thinking about Biological Variability and Change

• In Event: 3-134 - The Essence of Biological Categories: Factors Influencing Children’s Sensitivity to Variability and Change

Integrative Statement

In the biological domain, essentialist biases lead individuals to ignore trait variability (Emmons & Kelemen, 2015) and to view category boundaries as fixed (Shtulman, 2006). This makes it difficult for individuals to accept the idea that biological diversity within categories is related to historical biological unity by virtue of common ancestry. In the present study, we examine whether possessing a scientifically accurate understanding of evolutionary mechanisms, like natural selection, may help individuals overcome essentialist thinking about animal kinds because it provides them with a mechanism for representing how within-category variability (i.e., individual members of species differ) is related by the process of speciation to common ancestry (Kelemen, et al.,2014).

To assess participants’ acceptance of common ancestry, we presented them with 4 pairs of animals. Two pairs of animals were more perceptually similar (e.g., a buffalo and an elk) and two pairs of animals were less perceptually similar (e.g., a fox and a manatee ). For each pair, we asked participants whether they thought these two animals shared a common ancestor.

To assess participants’ acceptance of phenotypic variability in familiar animals, we randomly presented participants with 8 pictures each depicting a set of two adults and four offspring. In each picture, one offspring had different traits than its parents. For each picture, participants were asked whether it was possible for the two adults to have a child with atypical traits.

To assess participants’ understanding of natural selection, we used the interview protocol developed by Kelemen, et al. (2014). Participants were categorized as having or not having a foundational understanding of natural selection, i.e., not possessing any misconceptions and accurately mentioning differential survival advantage as a mechanism of natural selection.

We recruited 40 children and 40 adults (Children: 17 females, M=6.5; Range= 5 to 9; Adults: 31 females, M=42; Range= 31 to 54). On average, adults were more accepting of common ancestry, F(1,78)=9.27,p=.003, η2p=.11, and offspring variability than children, F(1,78)=5.39,p=.02,η2= .06. However, both children and adults tended to accept common ancestry when animals were perceptually similar but not when they were dissimilar, F(1,78)=127.03, p<.001,η2p=.62, Figure 1. Furthermore, both children and adults were skeptical that offspring could be born with species atypical traits. Children’s acceptance rate was no different from chance, t(39)=1.15,p=.26. Adults’ acceptance was marginally above chance, t(39)=2.05,p=.05, Figure 2. Importantly, however, this pattern of acceptance and rejection varied in association with individuals' understanding of an evolutionary mechanism. Children (n=8) and adults (n=31) who displayed a foundational or greater understanding of natural selection were more likely to accept common ancestry, F(1,78)=6.70,p = .011,η2=.08. Furthermore, their acceptance of common ancestry was correlated with their acceptance of greater within-category variability, rs(37)=.42,p=.008. This was not the case for individuals who did not display such an understanding, rs(39)=-.03,p=.85.

In summary, understanding natural selection was associated with a more coherent (and less essentialist) acceptance of how contemporary biological categories can vary greatly while sharing deep historical commonalities. Thus, teaching young children about adaptation through natural selection may help children understand the even more counterintuitive process of speciation.

Authors

• Samuel Ronfard, Boston University
  Presenting Author

• Deborah Kelemen, Boston University
  Non-Presenting Author