Selective Binaural Attention and Attention Switching

Abstract

This chapter examines the cognitive control mechanisms underlying auditory selective attention by considering the influence of variables that increase the complexity of the auditory scene concerning technical aspects such as dynamic binaural hearing, room acoustics, head movements, and interfering noise sources as well as those that influence the efficiency of cognitive processing. Classical research in auditory selective attention does not represent realistic or close to real-life listening experiences, of which room acoustics, distracting sources, as well as the dynamic reproduction of an acoustic scene including head movements, are essential parts. The chapter starts with an introduction to the subject of maintaining and switching attention from the standpoint of cognitive psychology. A paradigm suitable for the study of intentional switching of auditory selective attention is introduced through dichotic stimulus representation with different single number words (1–9, excluding 5) uttered by speakers of different gender presented simultaneously, one to the participant’s left ear and the other to the right ear. The listener is required to categorize, as quickly as possible, the target number as being either smaller or larger than five, with a visual cue indicating the listener’s task in each trial. This paradigm is gradually extended from dichotic reproduction to a complex dynamic acoustic scene to study the binaural effects in selective attention and attention switching, including different room acoustic conditions. Various technical possibilities are evaluated to validate the binaural reproduction of the spatial scene, minimizing errors on account of the acoustic virtual reality. Additionally, the influence of different binaural reproduction methods on the selective attention and attention switching model is carefully examined and compared to a natural listening condition using loudspeakers in an anechoic setting. The application of the binaural listening paradigm in anechoic conditions tests a listener’s ability to switch auditory attention in various setups intentionally. According to the results, intentional switching of the attention focus is associated with higher reaction times compared to maintaining the focus of attention on a single source. Also, particularly concerning the error rates, there is an observable effect of the stimulus category (i.e., stimuli spoken by target and distractor may evoke the same answer (congruent) or different answers (incongruent)). The congruency effect may be construed as an implicit performance measure of the degree to which task-irrelevant information is filtered out. The binaural paradigm has also been applied to older (slightly hearing-impaired) participants, with the results of which have been compared to experiments involving young normal-hearing participants, resulting in higher error rates and reaction times. Scenarios involving even more complex environments, including room acoustics (i.e., reverberation), have shown reaction times and error rates that rely significantly on reverberation time. Switch costs, in particular, reaction time differences between switch trials and repetition trials, can highly depend on the reverberation time.