The inclusion of human-like shapes like arms or faces in rather abstract pictures triggers the tendency of anthropomorphism, which is defined as the attribution of human characteristics to nonhuman objects. Anthropomorphism-triggering features in digital learning materials were found to enhance the performance of students. However, the probability of how effective such anthropomorphic features are might be dependent on the degree of the elicited anthropomorphism. In this study, 3 experiments were conducted to examine if varying degrees of anthropomorphism (low vs. medium vs. high) differently affect the learning performance of students. Participants were taken from different class levels; ranging from Class 5 and 6 (Experiment 1) to Class 8 and 9 (Experiment 2), and Class 11 to 13 (Experiment 3). The instructional material covered the topic of blood cell types. Subjective measurements of cognitive load, aesthetics, intrinsic motivation, and valence were included. Results show that an increased degree of anthropomorphism led to significant differences in the learning, intrinsic motivation, and aesthetics scores. The learning results of the 3 experiments were additionally checked by a meta-analysis. On a descriptive level, only students in Class 8 and 9 profited the most from a high degree of anthropomorphism. While students in Class 5 and 6 suffered from a high cognitive load in the high anthropomorphism condition, students in Class 11 to 13 were not as strongly affected by anthropomorphism as the other students. Results are partly explained by differences in prior knowledge. Educational Impact and Implications Statement: This study revealed that the inclusion of anthropomorphic features like faces into learning materials is a learning-enhancing design element. However, designers should be aware of the moderating role of domain-specific prior knowledge or the age of their target group. A high amount of anthropomorphic features is only helpful for students with a medium amount of prior knowledge, while students with either a low or a high level of prior knowledge only profit from a spare display of these features.