One of these theorists is Piaget. Piaget believed that children are active thinkers and that their minds develop through a series of universal, irreversible stages from simple reflexes to abstract reasoning. Throughout these stages, Piaget hypothesized that children's growing brains construct patterns that are used and adjusted through assimilation and accommodation. The first of these stages theorized by Piaget is the sensorimotor stage. This stage, which extends from birth to almost 2 years of age, is one during which infants experience the world primarily in terms of their sensory impressions and motor activities. Infants learn through adaptation, assimilation and accommodation. Infants also acquire object permanence, or the awareness that things continue to exist even when they are not perceived, during this period of rapid development. The preoperative phase occurs between 2 and 7 years of age. At this stage, children are learning to use language but are unable to execute complex logic. It is during this period that children develop a sense of self-centeredness, as well as a theory of mind, or the ability to read the mental states of others. Once a child reaches approximately 7 years of age, he or she enters a concrete operational phase that lasts until approximately 11 or 12 years of age. At this stage, children acquire the ability to think logically about concrete events. Piaget believed that during the concrete operational phase, children become capable of