This two volume set brings together the key research articles and papers on our basic attentional limitations when listening to two messages spoken at once and the major opposing theories which have sought to account for these limitations. It also includes the evidence which has been used to attempt to distinguish between these theories as well as contemporary analyses of the role of attention in the regulation of verbal and non-verbal behaviour.In addition to milestone research papers which set out our attentional limitations and the major explanations of these limitations, the articles in these two volumes represent contemporary investigations of attention and consciousness by experimental psychologists.