PMC4550780_01
Examples of complex recursive structures with one and two levels of embedding: Center-embeddings in German (top panel) and cross-dependencies in Dutch (bottom panel). The lines indicate noun-verb dependencies.
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F1
These two types of recursive constructions produce multiple overlapping non-adjacent dependencies, as illustrated in Figure 1, resulting in rapidly increasing processing difficulty as the number of embeddings grows. Christiansen and Chater, Forthcoming, for discussion). Can our limited ability to process multiple complex recursive embeddings similarly be shown to reflect constraints on sequence learning? The embedding of multiple complex recursive structures:whether in the form of center-embeddings or cross-dependencies:results in several pairs of overlapping non-adjacent dependencies (as illustrated by Figure 1).
Human performance (from Bach et al.,) on center-embedded constructions in German and cross-dependency constructions in Dutch with one or two levels of embedding (left). SRN performance on similar complex recursive structures (from Christiansen and MacDonald,) (right).
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F2
Figure 2 shows the results of the Bach et al. study on the left-hand side. The right-hand side of Figure 2 shows the mean sentence GPE scores, averaged across 10 novel sentences.