The contribution of individual words to the meaning of sentences

The studies purpose was assessing the contribution of individual words of a sentence to its overall intelligibility. The dependent variable was number of target words in each sentence correctly identified at each of three possible word positions, initial, middle, and last. The question of interest was how degradation of audibility of the initial word would affect other words by decreasing the semantic context for those later words resulting from the audibility of the first word. Other variables in the design included presentation levels that resulted in overall performance from 50 to 100 percent correct. There was a three way interaction of word position, masker, and presentation level on performance scores. Noise levels were fixed at 60 dB SPL, and speech levels were varied to -3, -6 and -9 signal-to-noise ratio (SNR). Between subject factors in the ANOVA design were SNR (-3, -6, and -9 db), and masker (flat or enhanced).