Example methods and systems determine viewing states, blinks, and blink intervals of an eye of a wearer of a head-mountable device. The head-mountable display can emit IR radiation from an associated IR radiation source toward a target location. An IR sensor associated with the head-mountable display can receive reflected IR radiation, such as the IR radiation emitted by the IR radiation source and reflected from the target location. The IR sensor can generate amplitude data for the reflected IR radiation. The head-mountable display can be used to determine a viewing state of the target location. The viewing state can be based on the amplitude data. The viewing state can determined from among a no-wearer-present viewing state, a wearer-present viewing state, a closed-eye viewing state, an open-eye viewing state, a non-display-viewing viewing state, and a display-viewing viewing state.
