A portable device with a touch screen display detects a contact area of a finger with the touch screen display and then determines a first position associated with the contact area. The cursor position of the finger contact is determined, at least in part, based on: the first position, one or more distances between the first position and one or more of the user interface objects; and one or more activation susceptibility numbers, each associated with a respective user interface object in the plurality of user interface objects. If the cursor position falls into the hidden hit region of a virtual push button on the touch screen display, the portable device is activated to perform operations associated with the virtual push button.