Like Mother, Like Daughter: Adults' Judgments About Genetic Inheritance

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. Public Significance Statement We studied adults' thinking about biology and found that they had some correct knowledge (such as understanding that offspring can look different from their parents), but also some misunderstandings (such as believing that offspring will resemble the parent of the same sex). This information can be used to tailor secondary and undergraduate genetics instruction to build on the knowledge students already have while correcting the misunderstandings they might hold.