Lexical and grammatical processing of unshadowed messages: A re-examination of the Mackay effect

Mackay (1973) claimed to have provided evidence that subjects could process the grammatical structure and lexical content of nonshadowed messages. In the present study, it was found impossible to repeat Mackay's findings when controls for several factors that had been ignored in Mackay's study were employed. Subsequent experiments indicated that two major factors contributing to Mackay's results were that he had a gap between sentences in his experiment and that the nonshadowed material came out of a background of silence. Both of these probably enabled subjects to switch attention to the nonshadowed material without disruption of shadowing performance.