In an earlier paper, we have argued that for subject-verb agreement, not only the grammatical number properties of the subject phrase are important, but also the notional number properties. Speakers make agreement errors when a grammatically singular head noun is combined with a grammatically plural local noun: #The bowl with the stripes are broken (versus The bowl with the stripe is broken). But more errors are also made when a grammatically singular head noun is combined with a notionally plural subject phrase: #The bowl with the spoon are broken (versus The bowl with the stripe is broken). This notional number mismatch effect appears to be additive to the grammatical number mismatch effect (attraction). In this paper, we investigated whether the two factors work independently from each other, by observing the change in agreement error rates when the notional number is made more salient.
One group of 
participants heard subject phrases with nouns that matched and mismatched in grammatical number, and subject phrases in which the notional number matched and mismatched with the head noun. Participants had to press a button for the singular or plural verb phrase with which they wished to continue the sentence. Another group of participants heard the same subject phrases, while being presented with a drawing of that subject phrase. This drawing made the notional number of the phrase very clear.
There were effects both of grammatical and notional number mismatch, which did not interact. Moreover, the notional number effect was stronger in the group that saw the drawings, whereas the grammatical number effect was identical across both groups. This suggests that notional and grammatical number information each have their independent influences on the agreement process.
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Alma Veenstra 
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