Do adults think about genetic inheritance as a deterministic or probabilistic process? Do adults display systematic biases when reasoning about genetic inheritance? Knowing how adults think about genetic inheritance is valuable, both for understanding the developmental end point of these concepts and for identifying biases that persist even after formal education. In two studies, we examined adults’ reasoning about genetic inheritance for familiar animals (Study 1) and unfamiliar animals (Study 2). First, participants were presented with animals that varied in eye color and were asked to judge whether each could be the offspring of a particular set of animal parents that had either the same or different eye colors. The potential offspring had eye colors that were either identical to the parents, blended the parents’ eye colors, or differed from the parents. Next, participants predicted how six offspring of the animal parents would look. Participants judged a variety of choices as possible—not only the ones resembling the parents—suggesting that they thought genetic inheritance was a probabilistic process. Additionally, many participants thought that female offspring would look more like their mothers and male offspring would look more like their fathers. Thus, systemic biases in reasoning about inheritance persist into adulthood.

An examination of life cycle diagrams from books and from an online database of science diagrams is presented. Many diagrams contained many irrelevant details, depicted the life cycle as a closed circle, and did not depict any form of biological variability. How these features might influence student learning and biological reasoning is discussed.

Do children think of genetic inheritance as deterministic or probabilistic? In two novel tasks, children viewed the eye colors of animal parents and judged (phenotypic judgement task) and selected (offspring selection task) possible phenotypes of offspring. Across three studies (N = 353) with predominantly White U.S. participants, 4- to 12-year-old children showed a probabilistic understanding of genetic inheritance, and they accepted and expected variability in the genetic inheritance of eye color. Children did not show biases identified in prior literature (i.e., mother bias) but they did show two novel biases: perceptual similarity and sex-matching. These results held for familiar and unfamiliar animals and persisted after a lesson, suggesting children use a biased probabilistic model to think broadly about genetic inheritance.

Do people think about genetic inheritance as a deterministic or probabilistic process? Do adults display systematic biases when reasoning about genetic inheritance? Knowing how adults think about genetic inheritance is valuable, both for understanding the developmental endpoint of these concepts and for identifying biases that persist even after formal education. We examined adults’ reasoning about genetic inheritance for familiar and unfamiliar animals. First, participants were presented with animals that varied in eye color and were asked to judge whether each could be the offspring of a particular set of animal parents that had either the same or different eye colors. The potential offspring had eye colors that were either identical to the parents, blended the parents’ eye colors, or differed from the parents. Next, participants predicted how six offspring of the animal parents would look. Participants judged a variety of choices as possible—not only the ones resembling the parents—suggesting that they thought genetic inheritance was a probabilistic process. Additionally, many participants thought that female offspring would look more like their mothers and male offspring would look more like their fathers. Thus, systemic biases in reasoning about inheritance persist into adulthood.

No abstract