1. A system, comprising: a data collector to obtain first response data from a first frequency band and second response data from a second frequency band of brain activity of a subject exposed to an advertisement or entertainment, the first frequency band and the second frequency band being different and occurring at a first time; a response systhesizer to: detect a first pattern of oscillation in the first frequency band; detect a second pattern of oscillation in the second frequency band; identify a degree of phase synchrony between the first pattern from the first frequency band and the second pattern from the second frequency band by detecting a repeating sequence of relative phase angles between the first pattern of oscillation in the first frequency band and the second pattern of oscillation in the second frequency band; and an effectiveness estimator to determine an effectiveness of the advertisement or entertainment based on the degree of the phase synchrony at the first time.