Some studies use a "probe verification" task rather than an overt acceptability judgment; in this paradigm, each experimental sentence is followed by a "probe word", and subjects must answer whether or not the probe word had appeared in the sentence. This task, like the acceptability judgment task, ensures that subjects are reading or listening attentively, but may avoid some of the additional processing demands of acceptability judgments, and may be used no matter what type of violation is being presented in the study.