Did you know you can read people's minds? This mind-reading ability, otherwise known as theory of mind, is something we develop at around 1-5 years old (depending on your definition).
Imagine you, a friend and a 2-year-old are eating Pringles. The friend goes away to another room. You decide to empty all of the Pringles from the tube to the trash and fill the tube with pencils. Once the operation is done, your friend comes back to the room. You ask the 2-year-old: "What does my friend think is in the tube?"
A child without theory of mind would say "pencils". A child with theory of mind would say "Pringles", knowing that your friend believes so even if reality is different.
A complete theory of mind is important for empathy, anticipating other people's reactions, understanding beliefs, communication and so much more. If you think about it, you're constantly mind-reading people, even without being aware of it.
There are various mind-reading tasks we engage in, and we usually learn them in this order: