Message comprehension as a function of intelligibility and advance knowledge of the topic

The relationship was investigated between estimated intelligibility (EI) and message comprehension (ability to answer questions presented at various levels of intelligibility). In Exper. I, 10 young adults identified the S/N ratio they associated with 0, 25, 50, 75, and 100% intelligibility for easy story material in speech-shaped noise at a constant 75 db SPL; subsequently, at the S/N's thus determined, comprehension was measured with easy short-answer questions. There was a very strong relationship between EI and comprehension, suggesting that the two were more or less synonomous. In Exper. II, comprehension with easy short-answer questions was measured at EI's of 25, 50, and 75% when each question was preceded by relevant, irrelevant, or no cues to the general topic of the question. Relevant cues had a positive effect which was significant at the 25 and 75% EI levels. The suggestion from Exper. I on the identity of EI and comprehension was modified to show that EI levels are a psychoacoustic variable which can be used to identify a regular decrease in comprehension when the speech signal is progressively masked by speech-shaped noise, but that the actual level and rate of decrease in intelligibility is a function of other factors, including psycholinguistic features of the message itself.