A key debate in the psycholinguistic study of grammatical language production is whether the process is a syntactocentric one, driven by grammatical information and grammatical rules, or a dynamic, interactive one, involving both semantic and syntactic information. Examining how speakers produce subject-verb number agreement has been useful in addressing this debate. Verb agreement is widely considered to be primarily a syntactic process in which grammatical number features of the subject are copied onto the verb. Variation in verb agreement patterns can, however, reflect the construal of the subject number. Such variation suggests that speakers are sensitive to both syntactic and semantic information about the subject during the production of agreement. However, psycholinguistic accounts of how speakers integrate these two types of information cannot yet account for the full range of variation seen in agreement in spontaneous, natural speech. This dissertation concerns a subject-verb number agreement pattern that cannot be explained either in terms of grammatical form or semantic construal of the subject, exemplified by the utterance ["One thing I thought about the other day"]-SG were-PL "batteries." The research presented here examines how verb agreement is affected by grammatical and semantic features outside of the subject noun phrase: the number of the post-verbal nominal, the concreteness of the post-verbal noun relative to the subject, and the semantics of the construction in which agreement is produced. I used a corpus study and three elicited production experiments to investigate how these features correlated with speakers' likelihood of producing verb agreement that did not match the grammatical number of the subject. Results demonstrate that speakers are sensitive to both grammatical and semantic information outside of the subject when producing verb number agreement. Specifically, the grammatical number of the post-verbal nominal affects speakers' production of verb agreement. Furthermore, the effects of post-verbal number are modulated by constructional semantics. These findings cannot be accounted for by syntactocentric models of language production, in which grammatical forms are processed in isolation from semantic information. Rather, they suggest that grammatical language production is an interactive process in which semantic information can modulate the effects of activated syntactic features. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]