While a device is in an unlocked state, a sequence of one or more activations of a button of the device are detected, where a first activation of the button is detected while a respective application user interface is displayed on the display. In response to detecting the sequence of one or more activations of the button: if the sequence of activations of the button meet first criteria, display of the respective application user interface is replaced with display of a different user interface while maintaining the device in the unlocked state; and if the sequence of activations of the button meet second criteria, the device switches from the unlocked state to a locked state, where the first criteria are differentiated from the second criteria based on a number and/or timing of activations of button in the sequence of activations of the button.