Editor’s note: Brain Basics from Scientific American Mind is a series of short video primers on the brain and how we feel, think and act. Below is a synopsis of the ninth video in the series written by a guest on this blog, Roni Jacobson, a science journalist based in New York City.

By Roni Jacobson

Cognition refers to higher order mental processes such as thinking, knowing, remembering and communicating. One of the first people to detail how cognitive ability develops throughout childhood was Swiss psychologist Jean Piaget. Piaget divided cognitive development into four stages: “sensorimotor,” which extends from birth to nearly age two, “preoperational,” which runs from ages two to seven years, “concrete operational,” which is in effect up to age 11 years, and “formal operational,” which is the stage young people enter at age 12 years.

Each of these stages, Piaget hypothesized, was marked by a unique pattern of reasoning. Babies in the sensorimotor stage use their senses and behaviors to understand the world. Yet they lack adult cognitive abilities such as “object permanence,” a term that means an awareness that things exist even when they are out of sight. In the following preoperational stage, Piaget believed that children still cannot perform various mental operations. They do not, for example, understand the idea that certain properties of a substance, the amount of juice in a cup, say, remain unchanged even if it changes shape—after, say, being poured into a taller glass. Preschool kids are also unable to perceive the world from another person’s point of view, although they eventually grow out of their egocentricity and develop “theory of mind,” which is an ability to understand that other individuals have ideas, wishes and intentions that may differ from their own.

The concrete operational stage is defined by the ability to engage in logical thinking and by the teenage years, young people can think abstractly and deal with hypotheticals, Piaget proposed. Today, child psychologists believe that Piaget’s developmental stages are more flexible than he initially thought, with more room for individual variation, but his constructs remain influential. This video provides a brief summary of Piaget’s classic stages of child development.

Other Brain Basics videos:

Multitask at Your Own Risk

Is Your Sense of Humor in Your Genes? Geneticists Crack the Code

Acts of Kindness Explained

Remember When…How Your Brain Builds A Memory

Terrified or Hopping Mad? What’s Going on Inside You

A Transformation of Light: How We See

Quick! What Is The Word for a Pair of Opposites?

The Hidden Power of Others Over You