Developmental trajectory of understanding plants, animals, humanoids, supernatural agents, and invisibility

We investigated the developmental trajectory of beliefs about plants, animals, humans, and supernatural agents among 108 participants (age 4 – adult). Participants viewed a cartoon story wherein an alien (humanoid) interacts with an alien plant, an alien dog, and a supernatural agent. Afterwards, participants were asked a series of questions about each entity’s physicality, physiological ability to move around, and ability to think and sense. Next, verbal ability was assessed (using BPVS-2). Finally, the participant had an “invisibility test” to investigate their understanding of invisibility. In our results, we found that people are most certain about things they can see (plants, animals, humans) and uncertain otherwise. Hence, children learned fairly quickly about plants, animals, and humans (although they tended to anthropomorphise the animals and at younger ages regarded the plant more like an inanimate object). Regarding supernatural agents, there was considerable confusion that persisted into adulthood. However, for the supernatural, there was a conspicuous bias toward regarding them as being able to move and understand. The idea of animacy and cognition seemed to go together. Also, there was an unexpected bias towards assuming that the supernatural agent needs to eat. Regarding invisibility, we found that children understand the concept by age 5.