This is Hidden Brain, I'm Shankar Vedantam.

All parents have moments when their kids test their patients.

Lian Yang is no exception.

I often yell at my kids for things that they did by accident,

like spilling a smoothie or leaving a cap off of a permanent marker

and, you know, making black permanent stains all over the sofa.

When this happens and the couches covered in black splotches or their smoothie on the floor,

the perpetrators inevitably offer this defense.

It was an accident. It's not my fault. I didn't mean to do it.

I shouldn't say this, but I tell them it doesn't matter that you didn't mean to do it.

What matters is that you won't do it again.

Lian's reaction, while understandable, is deeply ironic.

She's a psychologist who studies how we read other people's intentions.

We need to think about other people's minds in order to figure out who our friends are,

who to avoid, whom to punish, whether to punish,

and we need to read people's intentions in any ordinary interaction,

like having a conversation and figuring out what to say and how to respond.

As we go through life, we are constantly making sense of people's actions

by interpreting their intentions.

Our ability to read what is happening in other people's minds

is like an invisible compass guiding us through life.

But sometimes, it leads us astray.

...