Right/Left Brains & Human Auditory Perception

The Right / Left hemisphere Concept & Human Auditory Perception

By Max Stanley Chartrand, Ph.D.

One of the most persuasive arguments for the validity, indeed, the necessity, of binaural hearing aid fittings lies in how humans use the two hemispheres of the brain. Within this context we find process specialization in the various symbols of language to form whole communication.

Many years ago this author attended a course on rehabilitative speech pathology where a most amazing "theory" was being presented. It was proposed that the left hemisphere provided the technical backdrop in psychological processing of communication, while the right hemisphere provided the aesthetic mode. It was then hypothesized that the two hemispheres together provide the brain with an enormous capacity for cognizance of the aesthetic qualities of life while simultaneously interpreting abstract "meaning". Since that long ago hypothesis, virtually thousands of studies have proven the validity of such speculation.

Hence, we will cite only a few of those, along with their powerful implications that binaural hearing is much more preferable to monaural. In the fields of psychology (Corvallis and Beale, 1976), art (Arnheim, 1954), music (Critchley, 1977), education (Bruner, 1962), speech (Paivio, 1971), and others this principle has long been a major consideration in matters of curriculum and therapy. Aspiring artists (Arguelles, 1975) have long trained in the concept that they can intentionally develop cognitive shifts in their artistic skills. A cognitive shift is described as the ability to transform from one mental state to another, e.g., from L-mode to R-mode, or vice versa. In this way one could develop both abstract and expressive abilities in their artwork.

Bi-hemispheric principles adapted from the psychology field are particularly useful in the area of auditory rehabilitation. In the literature we find that the language-mediation areas of the superior temporal lobes of the human brain are significantly larger on the left side than on the right (Gerchwind and Levitsky, 1968)(Witelson and Pallie, 1973). This would make improvements in speech discrimination more critical for the right ear, which lateralizes primarily to the left hemisphere. This concept provides neurophysiological credence to the long-held "right ear advantage" (Hellige, 1993). The left ear, favoring the right hemisphere, on the other hand fulfills a more holistic, aesthetic purpose in its perception of auditory stimulus (Ley and Bryden, 1979).

Furthermore, while the differences in processing general sensory information between the two hemispheres of the brain are often small, there are astonishing differences in perceiving music and speech/language communication (von Bonin, 1962). This and other research would indicate that communication, especially language---both expressive and receptive---dominates in the left brain, received primarily by the right ear. The left ear, therefore, would provide mostly emotional and conceptual interpretation, an important component of intimate communication and in bonding in human relationships.

In the hearing health field, there are numerous examples that might be applied as evidence of this principle in action Fig. 1). In other words, the right ear (left brain) tells us what another person is saying. Is the message logical? Is the syntax and grammar correct? What is the "abstract" meaning of the message?

Likewise, the left ear may receive information helping one to perceive how another means what they are saying. Are they being cheerful? Sad? Sarcastic? Sincere? Deceitful? The left ear (e.g., right brain) is more likely to know the answer to those questions. Some might describe the information discerned by the left ear (right brain) as "intuition." Actually, this information---often described as "non-verbal" is an essential part of human communication, relying more upon voice stress, inflection, and psychosocial elements (Chartrand, 1999).

By combining both hemispheric interpretations of a single communication, or several connected symbolic subsets, we are capable of extracting significantly greater meaning out of everyday communication. Whereas, written communication can only convey essentially abstract communication, verbal communication brings immensely enhanced meaning to human communication.

These observations are particularly helpful in helping prospective hearing aid patients who may not yet appreciate or understand advantages of binaural hearing. For instance, after explaining the two separate functions of the ears, hearing professionals might ask, "Which is more important to you, to understand what a person says to you, or how they mean it?" Of course, put this way, any rational person would insist on binaural hearing. Hence, we have a reasoned and persuasive approach to justify the recommendation for binaural hearing aids, any subsequent contraindications notwithstanding.

Another application of the right/left concept: If one were to go to an orchestra concert, they would notice that the passage being listened to is, say, a Mozart Concerto, with a solo by the cello. The woodwinds and brass instruments provide the chordal background to the melody, while the tympani is quietly and gradually building in tempo and dynamic variations.

Emotional aspects of the music are being discerned via the right ear (toward the left hemisphere of the brain). We relax, allowing memories and imagination roam freely; emotions stirring with growing excitement and anticipation.

Technical aspects, such as form and analysis of the musical opus itself, including the realization that the violins carry the lead, supported in 6ths from the violas with the underlying fundamentals played by the bass violin section are all functions performed primarily through the right ear (toward the right hemisphere).

The combination of interpretations-from both hemispheres-allow us to enjoy the beauty and sparkle of music and the more abstract details of its writing, conduction, and performance. Without both messages, music loses more than half of its potential appeal. The same logic, therefore, may also carry over into human communication.

There are exceptions, of course, to recommending binaural correction in cases of bilateral deficits, though most of these can only be determined clinically, and rarely through the usual audiometric battery. Such exceptions would include Meniere's cases, post-stroke aphasia, hemiplegia, apraxia, and chemical/acoustic trauma of the cochlea.

Further, it should be noted that the right/left concept is not a cut and dried process, for though most neurological innervation of the central auditory system routes information contralaterally, a good deal of information is still routed ipsilaterally. However, the interpretive areas of the brain are still "wired" for specialization, while dichotic (two-eared hearing) comprises the normal human sensory configuration.

REFERENCES

Arnheim, 1954

Arguelles, 1975

Bruner, 1962

Chartrand, M.S., 1993

Corvallis and Beale, 1976

Critchley, 1977

Gerchwind and Levitsky, 1968

Hellige, 1993

Ley and Bryden, 1979

Paivio, 1971

von Bonin, 1962

Witelson and Pallie, 1973