Dichotic listening is a psychological test commonly used to investigate selective attention and the lateralization of brain function within the auditory system.
[5][6] He suggested that due to limited capacity, the human information processing system needs to select which channel of stimuli to attend to, deriving his filter model of attention.
[6] In the early 1960s, Doreen Kimura used dichotic listening tests to draw conclusions about lateral asymmetry of auditory processing in the brain.
[10][11] In the late 1960s and early 1970s, Donald Shankweiler[12] and Michael Studdert-Kennedy[13] of Haskins Laboratories used a dichotic listening technique (presenting different nonsense syllables) to demonstrate the dissociation of phonetic (speech) and auditory (nonspeech) perception by finding that phonetic structure devoid of meaning is an integral part of language and is typically processed in the left cerebral hemisphere.
An alternative explanation of the right-ear advantage in speech perception is that most people being right-handed, more of them put a telephone to their right ear.
The significant difference in this test is "the stimuli are constructed and aligned in such a way that partial interaural fusion occurs: subjects generally experience and report only one stimulus per trial.
"[27] According to Zatorre (1989), some major advantages of this method include "minimizing attentional factors, since the percept is unitary and localized to the midline" and "stimulus dominance effects may be explicitly calculated, and their influence on ear asymmetries assessed and eliminated.
In this version individuals listen to the same word in each ear but they hear it in either a surprised, happy, sad, angry, or neutral tone.
[28] The data from the emotional dichotic listening task is consistent with the other studies, because participants tend to have more correct responses to their left ear than to the right.
[32] Converging evidence from studies of attentional modulation of the VOT effect shows that, around age 9, children lack the adult-like cognitive flexibility required to exert top-down control over stimulus-driven bottom-up processes.
From this study, researchers concluded "dichotic listening as into a neuronal circuitry which also involves the frontal lobes, and that this may be a critical aspect of speech perception.
After reviewing many studies, it was concluded that "...dichotic listening should be considered a test of functional inter-hemispheric interaction and connectivity, besides being a test of lateralized temporal lobe language function" and "the corpus callosum is critically involved in the top-down attentional control of dichotic listening performance, thus having a critical role in auditory laterality.
In the early 60s, Doreen Kimura reported that dichotic verbal stimuli (specifically spoken numerals) presented to a participant produced a right ear advantage (REA).
[38] She attributed the right-ear advantage "to the localization of speech and language processing in the so-called dominant left hemisphere of the cerebral cortex.
In "Hemispheric Specialization for Speech Perception," by Studdert-Kennedy and Shankweiler (1970)[14] examine dichotic listening of CVC syllable pairs.
REA is the strongest when the sound of the initial and final consonants differ and it is the weakest when solely the vowel is changed.
Some data gathered from dichotic listening test experiments suggests that there is possibly a small-population sex difference in perceptual and auditory asymmetries and language laterality.
Green and colleagues tried to relate "the functional integration of the left hemisphere in hallucinating and nonhallucinating psychotic patients" using a dichotic listening study.
Further study on this matter was done by Phil Bryden and his dichotic listening research focused on emotionally loaded stimuli (Hugdahl, 2015).