1. An information displaying apparatus comprising: a displaying unit configured to display first content on a display; an audience state detecting unit configured to detect (i) a first audience state representing a physical state of an audience member positioned in front of the display at a first point in time, and (ii) a second audience state representing the physical state of the audience member positioned in front of the display at a second point in time after the first point in time; an interest degree estimating unit configured to estimate (i) a first interest degree based on the first audience state detected by said audience state detecting unit, the first interest degree indicating a degree of interest of the audience member in the first content displayed on the display by said displaying unit at the first point in time, and (ii) a second interest degree based on the second audience state detected by said audience state detecting unit, the second interest degree indicating the degree of interest of the audience member in the first content displayed on the display by said displaying unit at the second point in time after the first point in time, and; and a display control unit configured to (i) calculate a magnitude of a rate of change from the first interest degree to the second interest degree and (ii) cause said displaying unit to display second content with a clarity degree or an exposure degree of at least a part of the second content reduced below a predetermined clarity degree or a predetermined exposure degree when the magnitude of the rate of change from the first interest degree to the second interest degree is smaller than a first threshold.