The ability to correctly recognize and process ambiguous information is an important cognitive skill, though the neuronal correlates of false recognition of ambiguity have received insufficient study. The present investigation addressed verification of the hypothesis that there is a common neuronal marker for erroneous recognition of different types of ambiguous information as unambiguous. Ambiguous stimuli were verbal (anecdotes) and nonverbal (images with double interpretations) information presented to subjects visually as event-related potentials were recorded by electroencephalography. We expected that the neuronal correlate of this response might consist of so-called error-related negativity (ERN). ERN was detected only in the case of the erroneous perception of double images as unambiguous, but not in the case of erroneous perception of anecdotes as unfunny stories. We suggest that ERN can serve as markers for automatic monitoring of the correspondence of stimulus meaning with behavioral response and also as a measure of the level of awareness of the alternative meanings of a stimulus.