During the experimental task of dichotic presentation, subjects are asked to focus attention on one ear or the other while stimuli are being presented separately to both ears. Participants could accurately report what they were hearing in the attended ear, but they could report very little that had been presented to the nonattended ear. 

Dichotic Presentation: Shadowing

An interesting phenomenon regarding to event-related-potentials is noticeable during dichotic presentation. Overall, the ERP's for attended stimuli were larger in amplitude than when the same stimuli at the same ear were not being attended to. This N1 effect must have been caused by selective attention somehow acting on neural mechanisms to enhance processing of information from that ear. The prefix "N" refers to the negative voltage deflection of the event-related potential.

N1 Effect

This is another ERP , event-related-potential, finding based on the dichotic presentation studies. P3, a wave also called auditory P300, is believed to reflect higher-order cognitive processing of the stimulus (ie. semantic meaning of words, identification of the speaker, etc.). The P3 effect is an example of a late-selection effect of auditory attention. The prefix "P" refers to the positive voltage deflection of the event-related potential.

P3 Effect

In a task where a participant is told to identify/recall the different sounds coming through each ear, most people will identify sounds that come from the right ear more accurately than the right ear. (Note: 50%of left-handers experience the reverse, which is a left-ear advantage).



The Right-Ear Advantage in Dichotic Presentation

Dichotic presentation is where participants listen to two different streams of dialog delivered simultaneously to the left and right ears.

Johns Hopkins University

New York University

- Attentional Spotlight
- Dichotic Presentation
- Attentional Bottleneck

Examples of Divided Attention Tasks

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Attentional spotlight is the shifting of our limited selective attention around the environment to highlight stimuli for enhanced processing. Since it is impossible to process everything in our environment at once, we must isolate or "spotlight" was is truly important to us against the noisy background. 

Attentional Spotlight

Dichotic Presentation

One of the important functions of attention is to act as a filter, blocking unimportant stimuli and directing cognitive resources to only the most important  events, and thereby protecting the brain from being overwhelmed by the world.

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