Differences in the cognitive demands of word order, plural, and subject-verb agreement constructions.

The syntactic devices of subject-verb-object word order, regular plurals, and subject-verb agreement differ in age of acquisition and susceptibility to error within language-disordered populations. In the present article, the performance of adults on a grammaticality judgment task is used to explore whether such differences are related to working memory (both in terms of an externally imposed load and individual differences in capacity) and phonological ability. The results show that word order, the earliest acquired and most resilient device, is not affected by load, memory span, or phonological ability. Plurals are affected marginally by load and significantly by phonological ability. Agreement, the last acquired and least resilient device, is affected by load, memory span, and phonological ability. Thus, consistent with a processing-based explanation, later acquired and less resilient devices have higher working memory and phonological demands.