The ability to understand and to incorporate the rules of basic logical inference in everyday activities.

Regarded as a universal human trait, the ability to think logically, following the rules of logical inference, has traditionally been defined as a higher cognitive skill, typically beyond the ken of a very young child. The field of cognitive child psychology was dominated for more than half a century by the Swiss philosopher and psychologist Jean Piaget, whose seminal studies are considered fundamental. Piaget identified four stages of cognitive development: during the sensory-motor stage (ages 0-2), the child learns to experience the world physically and attains a rudimentary grasp of symbols; in the preoperational stage (ages 2-7), symbols are used, but thought is still "preoperational," which means that the child does not understand that a logical, or mathematical, operation can be reversed; the concrete operations stage (ages 6 or 7-11) ushers...