Download Devin St. John - Northeastern University

Agreement Interference in Sentence Comprehension: Evidence from Self-paced Reading
Devin St. John
Advisor: Neal Pearlmutter
Northeastern University
Sentence comprehension often involves linking words with agreement features over
variable distances. In English, for example, the number of the subject must match the number of
the verb; that is, singular subjects require singular verbs and plural subjects require plural verbs.
The comprehension system must keep track of these number features over time in order to
successfully compute agreement relations. The current study examines how these features are
tracked and the contexts in which difficulty processing subject-verb agreement might arise.
In a self-paced reading experiment, Pearlmutter, Garnsey, and Bock (1999) examined
processing of sentences in which two nouns preceded the verb. They varied the second noun’s
number as well as the verb’s number (e.g., The lock for the [cabinet/cabinets] [was/were] in the
drawer of the cupboard). When the verb was ungrammatical (were), a match in number between
the subject and the second noun resulted in slower reading times after the verb than a mismatch
in number. Conversely, when the verb was grammatical (was), reading times were faster when
the subject and second noun matched in number than when they mismatched. These findings
indicate that agreement features are continuously tracked over time in both grammatical and
ungrammatical cases, and that this tracking is susceptible to interference from distracting nouns.
Wagers, Lau, and Phillips (2009) contend that the slower performance in the
grammatical-mismatch condition was due to the complexity of the plural feature. That is, plural
nouns take more effort to process than singular nouns, which is reflected in slower reading times.
Because this additional processing load can carry over to the following sentence region, slower
reading times after the verb in the grammatical-mismatch condition may indicate “spill-over”
from the preceding plural noun, rather than an effect of mismatching nouns. Wagers and
colleagues expect to see a reading time difference between the ungrammatical conditions, but
they argue that there is no such difference between the two grammatical cases. Contra
Pearlmutter et al. (1999), this would indicate that the comprehension system ignores agreement
features until it encounters an ungrammatical verb.
To more clearly delineate the region of spill-over from the critical agreement region – the
verb and the following word – we extended the region between the second noun and the verb
(e.g., The lock for the [cabinet/cabinets], although left out earlier, [was/were] in the drawer of
the cupboard). Any spill-over from the plural noun should disappear by the end of this
intervening material. Thus, an effect of the second noun’s number at the critical region in the
grammatical conditions would indicate interference from the second noun, rather than spill-over
from the plural number marking.
The results from a self-paced reading experiment indicate that reading times for the
grammatical mismatch case were marginally slower at the critical region than for the match case.
If this effect bears out in subsequent experiments, it would indicate that feature tracking during
sentence comprehension is subject to interference from a distracting number-marked noun. This
would suggest that the comprehension system processes agreement features as they are read,
rather than only when an ungrammatical verb is encountered.