Referential processing: Evidence from eye tracking and ERPs

Peter C. Gordon
University of North Carolina at Chapel Hill

Tamara Y. Swaab and C. Christine Camblin
Duke University

Language comprehension involves the creation and the maintenance of a discourse model that embodies the meaning of a sentence (or a series of sentences) and which serves as a basis for the continued interpretation of linguistic input. Processing referential expressions can in some instances lead to the creation of new entities in the discourse model that must be stored in working memory while in other instances existing entities in working memory must be accessed in order to achieve a coreferential interpretation. A coordinated pair of studies, one tracking eye movements during normal reading and the other measuring ERPs during RSVP reading, was conducted to examine the impact of the memory requirements imposed by the number of entities in the discourse model and to examine how working memory is accessed during the comprehension of coreferential expressions. The experimental sentences manipulated two factors: (1) whether the first clause of the sentences had one name (singular condition) or two names (conjoined condition); (2) whether the referential expression in the second clause was a repeated name or a pronoun (see example). John (and Mary) went to the store so that he/John could buy some candy.

Both eye tracking and ERP measures showed effects of the number of names on the comprehension of the words following the matrix subject but before the coreferential expression. Gaze durations on those words were longer and ERPs showed a stronger negativity in the N400 region in the two-name condition than in the one-name condition. In
addition, both measures showed that the type of coreferential expression (pronoun versus repeated name) interacted with the number of names in the first clause. Of particular interest, gaze durations to repeated names were longer in the one-name (singular) condition than in the two-name (conjoined) condition, a pattern that was matched by a larger N400 to the repeated name in the one-name than in the two-name condition. This pattern is consistent with previous findings showing that repeated names are processed more readily when referring to non-prominent referents than to prominent referents.
The results show that eye tracking and ERPs provide consistent evidence about referential processing in discourse, with respect both to the memory requirements imposed by representing multiple discourse entities and with respect to how those representations are accessed during the establishment of coreferential relations.