A hand region is detected in a captured image, and for each part of the background area, a light source presence degree indicating the probability that a light source is present is determined according to the luminance or color of that part; on the basis of the light source presence degree, a region in which the captured image is affected by a light source is estimated, and if the captured image includes a region estimated to be affected by a light source, whether or not a dropout has occurred in the hand region in the captured image is decided; on the basis of the result of this decision, an action is determined. Gesture determinations can be made correctly even when the hand region in the captured image is affected by a light source at the time of gesture manipulation input.