Final answer:
The question relates to the field of Psychology, focusing on developmental milestones and behaviors. Psychologists use these insights to understand why a child may not be able to perform certain actions, involving stages of cognitive development, conditioning, and theory-of-mind.
Step-by-step explanation:
The question revolves around the developmental milestones and behaviors exhibited by individuals at different life stages, which is a characteristic subject of study within the field of Psychology. When discussing the reason a child cannot do something, psychologists often look to developmental stages, conditioning, and the child's environment to understand their behavior. For instance, an infant may put objects in their mouth as part of their sensory exploration, an integral part of their cognitive development. Similarly, an 11-year-old boy's bullying behavior might stem from how he has been conditioned by his environment or a possible manifestation of a resistant attachment style developed early in his life. A child's inability to perform a task could also be linked to a cognitive change such as the development of theory-of-mind (TOM), which allows them to recognize that others may have different thoughts and perspectives.