Previous studies of gradedness have failed to distinguish between the issues of typicality and category membership. Thus, data which have been taken to demonstrate that membership is a matter of degree may only demonstrate that typicality is graded. The present paper reports the results of two studies that attempt to overcome limitations of past methods. In the first study, subjects were asked to rate both typicality and category membership for the same stimuli as a way of distinguishing the two questions. A second study was based on the notion that there may be no definitive answer to questions about membership in graded categories. Thus, disagreements about membership in all-or-none and graded categories may have different qualities Stimuli included animal and artifact categories as well as animals that had undergone different kinds of transformations. Results from both studies suggest some support for claims that membership in animal and artifact categories is graded.

Lockhart and Keil have written an interesting monograph focusing on the development of reasoning about medicine, a relatively underexplored area of research with potentially broad implications with respect to the design of more-effective medical interventions. In a set of 15 studies with well over 2,200 participants, they examine how children and adults combine aspects of biological and psychological reasoning to create working models of medicine. Lockhart and Keil explore developmental changes in reasoning about illness and its treatment using medicines in terms of dualism (e.g., psychological vs. physical), spatial proximity, differential timing of effects, potential side effects, and treatment tradeoffs. This commentary highlights the novel contributions of this monograph, examines issues that need additional considerations, and makes suggestions for future research.

Genetic inheritance is a fundamental biological concept that is critical to understanding more advanced biological concepts. Diagrams are frequently used to aid learning in biology, though their presentation varies greatly. We examined teachers’ expectations about how different types of diagrams would influence learning outcomes. We chose representative diagrams based on our previous analysis of inheritance diagrams, focusing on features like detailedness, label usage, and diagram type (pedigree vs Punnett square). Science teachers (K-12) were asked to rate how well their students would learn from the presented diagrams in an online survey. Overall, teachers rated the diagrams highly. Most teachers believed Punnett squares would be more beneficial to students than pedigrees. Diagrams with labels and greater detail were also rated higher. We will discuss how these findings relate to previous research on diagram-based learning in science and the prevalence of preferred diagrams in educational materials.

Within-species variability is a fundamental biological concept, essential in understanding advanced concepts like evolution. Students formally encounter variability in their study of genetics in 4th grade; however, children’s cognitive biases can constrain their learning of variability. Diagrams are often used to facilitate learning of biological concepts, so it is important to understand how genetic inheritance diagrams depict variability. We analyzed 647 diagrams collected from textbooks and websites to examine how much variation diagrams present. We coded (1) depictions of within-species variability, and (2) other perceptual features implicated in learning (e.g., concreteness, richness). Preliminary findings indicate that many diagrams depict some within-species variability. Additionally, most diagrams used abstract representations of organisms and traits, which research suggests may be less optimal for younger students’ learning but may encourage transfer in older students. We will discuss how diagram features may reinforce children’s cognitive biases and may influence students’ learning of inheritance and variability.

Do children think of genetic inheritance as deterministic or probabilistic? In two novel tasks, children viewed the eye colors of animal parents and judged and selected possible phenotypes of offspring. Across three studies (N = 353, 162 girls, 172 boys, 2 non-binary; 17 did not report gender) with predominantly White U.S. participants collected in 2019-2021, 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 a mother bias but they did show two novel biases: perceptual similarity and sex-matching. These results held for unfamiliar animals and several physical traits (e.g., eye color, ear size, and fin type), and persisted after a lesson.

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. (PsycInfo Database Record (c) 2023 APA, all rights reserved).