A metaphor for when two people are in a relationship and Person 1 feels like they are a bird wanting to fly but are trapped inside of a cage (aka: Person 2).
It is basically a great way of telling someone you want to break-up due to your animalistic nature of being wild and free and not wanting to be tied down to them.
Anne: "Ricky, I'm feeling like our relationship is based off the Bird and the Cage theory.
Ricky: "Wait, what do you mean?"
Anne: "I mean that I'm a bird and you're a cage; I just want to fly."
Ricky: "Oh... *sobs uncontrollably*
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