Much research and debate around theory of mind (the ability to attribute mental states to actions) have revolved around whether X have a theory of mind. X might be 3-year-olds, infants, children with autism, chimpanzees, rhesus macaques, and so forth. I will argue that the better question is  what aspects or types of theory of mind are used by X. Numerous studies  have shown that children develop different components or aspects of  mental-state understanding at different ages, and nonhuman animals demonstrate some components of mental-state understanding in certain situations. Research in my lab has shown that children with different developmental disabilities and typically-developing children from different cultures have shared and non-shared trajectories in their developmental progression of understanding different mental states. In addition, we have discovered different neural circuitries associated with reasoning about different mental states. Our findings provide a framework for understanding similarities and differences in mental-state understanding across different human populations and different species.