An electronic device with a touch-sensitive surface, a display, and one or more sensors to detect intensity of contacts, detects a contact, determines a location and intensity of the contact on the touch-sensitive surface, and displays a response, the response being based at least in part on an input-output mapping of intensity to response at the contact location. The input-output mapping including a first input-output relationship between intensity and response over a first range of intensity values, a second input-output relationship between intensity and response over a second range of intensity values, and a transitional intensity value where the first range of intensity values meets or overlaps the second range of intensity values. At the transitional intensity value, the first input-output relationship has a first rate of change, the second input-output relationship has a second rate of change, and the first rate is substantially the same as the second rate.