By performing a comparison of words spoken by a speaker and defined material which is presented to the speaker, information can be determined which allows for the convenient control of the presentation of material and external devices. A comparison of a speaker's words with defined material can be beneficially used as an input for controlling the operation of an exercise apparatus, video games, material presented to an audience, and the presentation of the material itself. Similar feedback loops can also be used with measurement and stimulation of neurophysiologic states, to make the activity of reading more enjoyable and convenient, or for other purposes.