System, recording medium, and method for estimating user's psychological state

A system according to a certain embodiment of the present disclosure is provided with: a light source that emits pulse light to be applied to a user's head; an optical detector that detects at least a part of reflected pulse light having returned from the head and that outputs one or more signals corresponding to the intensity of the at least a part of the reflected pulse light; an electric circuit that controls the light source and the optical detector and that processes the one or more signals outputted from the optical detector; and a memory that stores an emotion model indicating the relationship between the one or more signals and a plurality of emotions. On the basis of change of the one or more signals, the electric circuit selects at least one emotion from among the plurality of emotions with reference to the emotion model. The one or more signals include a first signal corresponding to the intensity of a first portion of the reflected pulse light, and a second signal corresponding to the intensity of a second portion different from the first portion of the reflected pulse light. The first portion includes a portion before start of a falling period, and the second portion includes at least a part of the falling period.