What is the Barnum effect (Forer effect)?

We accept vague, general statements as uncannily accurate descriptions of ourselves, even though they'd fit almost anyone.

The mechanism combines confirmation bias with a wish to be understood: a statement loose enough to apply to everyone gives us room to fill in our own specifics, and we then read our personalised version as evidence the description "really gets me." We notice the parts that fit and ignore the parts that don't.

Example: "You have a great deal of unused potential, and at times you're outgoing while at other times reserved." It feels personal, yet it's true of nearly everyone — which is exactly how horoscopes, cold readings and many personality tests create their illusion of insight.

Tip: Before being impressed by how well a description fits you, ask "would this also fit my completely different friend?" Usually it would.