A “Contact Discriminator” provides various techniques for differentiating between valid and invalid contacts received from any input methodology by one or more touch-sensitive surfaces of a touch-sensitive computing device. Examples of contacts include single, sequential, concurrent, or simultaneous user finger touches (including gesture type touches), pen or stylus touches or inputs, hover-type inputs, or any combination thereof. The Contact Discriminator then acts on valid contacts (i.e., contacts intended as inputs) while rejecting or ignoring invalid contacts or inputs. Advantageously, the Contact Discriminator is further capable of disabling or ignoring regions of input surfaces, such tablet touch screens, that are expected to receive unintentional contacts, or intentional contacts not intended as inputs, for device or application control purposes. Examples of contacts not intended as inputs include, but are not limited to, a user's palm resting on a touch screen while the user writes on that screen with a stylus or pen.