When I was running earlier subject-verb agreement experiments, I noticed that some people make a lot more agreement errors than others. Although the overall mean error rates were similar to the existing literature, I became intrigued by the large individual variation in agreement production.
Some studies had already shown (some more convincingly than others) that working memory might have something to do with it. We also hypothesized that inhibitory control might prove useful in producing correct agreement. Remember the sentence “the key to the cabinets are missing”? Whereas the number of the head noun has to te kept active until the point in time where the agreement link with the verb is made, the number from the local noun has to be inhibited so that the verb does not accidentally agree with the local noun.
We tested this hypothesis with two groups of children: monolingual Dutch speakers and bilingual French-Dutch speakers. Some studies have suggested that bilinguals have better executive control skills than monolinguals. If these skills are needed for agreement, bilinguals might be better at agreement production as well.
All children completed a agreement production task (which we first introduced here), a verbal and a non-verbal working memory task, a switch task, and the Attentional Networks Task. A bit to our surprise, the monolingual and bilingual children did not differ in their executive control skills or in their agreement error rates. However, we did find overall correlations of verbal working memory with agreement error rates: children with a higher working memory made fewer errors. Although there was a trend for inhibitory control in the hypothesized direction, this effect did not reach significance. More children are being tested to see whether this is a power issue.
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Alma Veenstra 
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