Theory of Mind

The Sally-Anne Test

Sally

Anne

"My marble is in the basket"

"I'll move the marble..."

Basket

Box

This is Sally and Anne. Sally has a marble that she loves.

Where will Sally look for her marble?

Theory of Mind

Understanding that others have different thoughts

Theory of Mind is the ability to understand that other people have their own thoughts, beliefs, and knowledge—which may be different from yours.

The Sally-Anne test (1985) is a classic experiment by Simon Baron-Cohen that reveals when children develop this ability.

Children under ~4 typically fail this test. They say Sally will look in the box (where the marble actually is) because they can't separate their own knowledge from Sally's.

Around age 4-5, most children begin to understand that Sally doesn't know what they know—she has a "false belief" about where her marble is.

Pass Rate by Age

3 years

~15%

4 years

~50%

5 years

~85%

Adults

~98%

Why it matters: Theory of mind is fundamental to social interaction, empathy, deception, teaching, and understanding that someone can be wrong about something you know to be true.