What skill is a hallmark of the formal operational stage in Piaget's theory?

Hypothetical reasoning is a defining feature of the formal operational stage in Piaget's theory of cognitive development. This stage, which typically begins around age 12 and extends into adulthood, is characterized by the ability to think abstractly and logically. Individuals in this stage can consider hypothetical situations and reason about them systematically, moving beyond the concrete experiences that dominate earlier stages.

This capability allows for problem-solving that involves potential outcomes and various scenarios, enabling more advanced forms of thinking, such as scientific reasoning and planning for the future. It represents a significant leap in cognitive ability, as individuals can now manipulate ideas and concepts in their minds without relying solely on physical objects or real-life experiences.

Other options focus on different cognitive aspects. Concrete manipulation of objects relates to the previous operational stage where children engage with tangible, concrete phenomena. Emotional understanding pertains to interpersonal or social development rather than cognitive development, while basic arithmetic falls under the foundational skills typically developed much earlier in childhood and does not reflect the advanced cognitive capabilities of the formal operational stage. Thus, the hallmark of this stage is indeed the ability to reason hypothetically.