Newbie question: C programing for AVR
The behavior you describe most likely indicates that the switch closure is causing the port bit to read low, not high.

This would be quite normal, as it is fairly traditional to use a pull-up resistor to put a deterministic state on an input when the connected switch is open, and have the switch closure override this by connecting to ground.

While some other microcontrollers can be configured with either an internal pull-up or an internal pull-down, the AVR offers only internal pull-up resistors.  To do things the other way around, with a button that signalled high when the contacts were closed, you would need to use an external pull-down resistor.