LEXICAL DENSITY AND PHRASE STRUCTURE DEPTH AS VARIABLES IN SENTENCE RETENTION

Two variables, one syntactic and one lexical, were investigated for their effect on the retention of spoken English sentences. Mean phrase structure depth (d̄), based on the Yngve syntactic model, and lexical density (LD) were varied in a 2 × 2 within-subjects design, with List adding a between-subjects variable. The main results were that recall probability of individually presented sentences was not related to d̄, but was inversely related to LD, the proportion of lexical, as opposed to grammatical, words in the sentence. These results were replicated with a third list. The fact that d̄ was unrelated to retention casts further doubt on the general value of the Yngve hypothesis, at least as presently interpreted and approximated by the d̄ measure. Alternative interpretations of the model are briefly discussed. Finally, explanation of the LD effect is discussed in terms of lexical uncertainty and underlying relations. © 1969 Academic Press Inc. All rights reserved.