Download Title: What is Pitch, and How is it Perceived in the Brain

Title: What is Pitch, and How is it Perceived in the Brain
Group 5
Group Members:
Carlton Davis
David Givens
Marion Lykins
Karen Wheeler
Evan White
Stephanie Zier
Class: EDP 101C
Introduction:
The human perception of sound is a process where the ears and brain work
together, as a series of spiral sheets and brain cells. Human ears are capable of picking
up a wide variety of frequencies and sounds, while the brain processes the incoming
information and interprets the meaning of what is heard. In the course of discussing
music and cognition, this group explored the relations between music and intelligence.
This discussion led to the questions about pitch and perception, which eventually led to
questions about perfect pitch and Amusia.
This group’s paper focuses on discovering what pitch is, and how it is perceived it
in the brain. Additionally, why do certain people excel at perceiving pitch, and why are
other people completely incapable of perceiving pitch. The answers to these questions
will be found by exploring several concepts: pitch, how the brain processes sound,
perfect pitch and its development, and Amusia.
Any discussion of perfect-pitch and Amusia must first begin with a discussion of
pitch itself. Musically speaking, pitch is a sound that is heard, in contrast to a specific
note, which is a name for a pitch that indicates how the pitch functions in relation to the
other pitches in a specific musical context. (Cooke, 2007-2008, New Grove Dictionary of
Music).
A more scientific definition of the word pitch, provided by Levitin, is: “The word
pitch refers to the mental representation an organism has of the fundamental frequency of
sound. That is, pitch is a purely psychological phenomenon related to the frequency of
vibrating air molecules. … Sound waves-molecules of air vibrating at various
frequencies-do not themselves have pitch. Their motion and oscillations can be
measured, but it takes human (or animal) brain to map them to that internal quality we
call pitch” (Levitin, 2006, pp 22). In short, pitch is a brain’s interpretation of sound
waves.
It is important to note that measurements of sound waves described above are
measured in Hertz, or Hz. For example, many orchestras tune to an “A” before a concert,
where this A sounds to a frequency of 440 Hz. When the orchestra tunes to the note “A”,
they are in reality tuning to a specific frequency. Another interesting fact about pitch is
that an “A” sounding at the frequency of 442 Hz will still sound like an “A” to a
listener’s ears. In fact, from 1762-89 the turning note “A” varied between frequencies of
377 and 428 Hz (Matthews, 2002, pp 53). Furthermore, since pitches are comprehended
in relation to other pitches, as long as the orchestra plays the other notes proportionally
sharper, the audience is unlikely to think the orchestra is playing “sharp”.
Another interesting fact to point out about pitch is that no animal can hear a pitch
for every frequency that exists (Levitin, 2006, pp 24). A human, can on average, hear
sounds from 20 Hz to 20,000 Hz. To put this into perspective, the lowest key on a
piano’s keyboard sounds at 27.5 Hz, and one of the highest notes a piccolo can sound
(C8) is 4186.0 Hz (Levitin, 2006, pp 23). In fact, sounds above 6000 Hz and more,
sound like high-pitched whistling to most people. So, bringing the discussion back to a
musical context, the range of musical notes that convey the strongest sense of pitch, range
from 55Hz to about 2000Hz (Levitin, 2006, pp 26).
While a sound wave, does not have pitch, per se, its motions and oscillations are
mapped by the brain, and thus pitch is perceived. The ability to detect pitch is based on
physiology, and varies from one animal to another. Basilar membranes in the inner ear
contain hair cells that are frequency selective. The membrane is located in the cochlea of
the inner ear, where movement of the cochlear fluid causes it to vibrate. The organ of
Corti is the structure located on the basilar membrane of the inner ear that contains the
actual auditory receptors. (Davis, 2007, pp 102)
The lower the frequency sound of a pitch, the farther towards one side of the
basilar membrane it is. The hair cells are spread out according to how intense the
frequency is that excites it. Those hair cells that are excited by very high frequencies are
on the other side of those that respond to low frequencies. There is an outlay of hair cells
stretched across the cortial surface called the tontotopic map. Electronic signals are sent
from here up to the auditory cortex for more processing (Levitin, 2006, pp 32).
Whatever hertz at which a tone is played, the brain electrodes emit electrical
activity of an identical frequency. Unknowingly, the brain keeps track of how many
times particular notes are sounded. The computational process in the brain makes an
inference about the key the note is in based on a few properties which include: how many
times the particular notes are sounded, whether or not they are strong or weak beats, and
how long they last. Amazingly, humans can process tones without any musical training
or declarative knowledge. Additionally, more often and longer a pitch is played, the
better one can perceive it (Levitin, 2006, pp 35).
There have been many studies conducted concerning how pitch affects parts of
the brain that lead to emotions. For example, in the occurrence of an unpleasant pitch,
the posterior cingulate cortex is affected, which triggers conflict and emotional pain. The
theories that pitch affect emotions can be observed in everyday life. For example, people
react differently when people use different tones with them. A more aggressive pitch
leads to a sense of fear and uneasiness, where a more relaxed pitch creates a more
comfortable environment. (Luu, 2003, Oxford Journals Online)
As stated earlier, a hertz is a unit of measure of the frequency of a sound wave
(Davis, 2007, pp 102). It was also noted earlier that rather than the existence of a
specific frequency for each note, there is a general range of frequencies, which can be
interpreted as a note. Our perceptions of notes relative to other notes, is thus based on
proportions, not specific frequencies. The distance from one pitch to the next is a musical
system that is spaced out equally. The frequency level of the next note up the scale is
exactly 6% greater than the previous one, and vice versa. Our auditory systems are
sensitive to relative and proportional changes in pitch, so each 6% increase in frequency
seems to be the same amount. The organization of the cells that are responsive to pitch
change from daily to monthly. Interestingly, though, people that have what we call
“perfect pitch” rarely experience changes in these cells, which is what allows them to
recognize “perfect pitch” (Levitin, 2006, pp 38).
But what is perfect pitch? Perfect pitch, also referred to as absolute pitch, is the
ability of a person to name or recreate a pitch without needing to hear a reference. When
a person with absolute pitch hears any note, they are able to instantaneously and without
thought name the pitch. They may have a wide range of abilities that could include:
identifying and naming individual pitches played on instruments, naming pitches of
common everyday noises, singing a given pitch without any reference, naming the key of
a given piece of tonal music, and/or identifying and naming all of the tones of a given
chord. Absolute pitch can be found in people in varying degrees, but most with it can
identify up to about seventy tones. While a person with relative pitch may need to hear a
reference point in order to identify a pitch, those with absolute pitch identify each pitch
with “a unique and characteristic quality that distinguished it absolutely from any other
note” (Oliver Sacks, 2007, pp 120). It is as though they have acquired another sense and
it seems odd to them that not everyone possess it.
Many people with perfect pitch compare this ability to seeing color. Just as most
people can look at a banana and immediately identify it as yellow, individuals with
perfect pitch can hear a tone and immediately identify its pitch, without any thought
processing. One man explains, “he perceived pitches instantly, absolutely, as he
perceived color- no mental process was involved, no inference, no reference to other
pitches or intervals or scales” (Oliver Sacks, 2007, pp 124).
Absolute pitch is a psychological fiction, just like color, in that our brains create a
categorical structure (Levitin, 2006, pp 151). Absolute pitch is not a heightened ability to
perceive and discriminate fine gradations of sound frequencies, as an absolute listener's
sense of hearing is no keener than that of a non-absolute.
Absolute pitch is very rare, occurring in less than one in ten thousand and is not
universal (Levitin, 2006, pp 149). It has been found to be more common among speakers
of tonal languages, such as Chinese or Vietnamese, which depend heavily on pitch for
lexical meaning. This suggests that absolute pitch may develop in infants when they learn
to speak in a tonal language or in a pitch stress language. However, further studies show
that if these individuals receive musical training they will be more likely to acquire
absolute pitch. Level-tone languages found in Africa may also be better suited to acquire
absolute pitch compared to contour-tone languages of East Asia. Speakers of non-tonal
languages, such as English, are less likely to acquire absolute pitch compared to speakers
of tonal languages.
There is also a correlation between the age of musical training and the
development of absolute pitch. The ages of eight and younger have been identified as the
critical period for the development of absolute pitch. A study showed that when students
were trained at ages 4 and 5 60% of the Chinese students and only 14% of the US nontonal language speakers acquired absolute pitch (Oliver Sacks, 2007, pp 127). Once they
trained students above the age of eight, none of the US students acquired absolute pitch
and only 42% of the Chinese students did. Researchers have come to the conclusion that,
“absolute pitch may be universal and highly adaptive in infancy, but becomes
maladaptive later and is therefore lost” (Oliver Sacks, 2007, pp 129). Another study was
done in which a pre-school group of students and an adolescent group of students were
musically trained for six weeks. Results showed that, “the pre-school group showed
significant improvements in reference tone identification and reproduction, compared
both with themselves and with the adolescent group” (Crozier, 1997, pp 110). While there
are many similarities in the auditory processing of infants and adults, studies have shown
that pitch processing and knowledge of tonal structure, change throughout development.
Results from experiments have shown that adults process both absolute and relative pitch
patterns, whereas infants process absolute pitch patterns in continuous tone sequences
(Saffran, 2003, pp 35).
There are many other factors, other than age and language, that can also affect
an individual’s development of absolute pitch. Genetic differences are believed to play an
important role in absolute pitch development. Some researchers are attempting to locate
genetic correlates in order to find an underlying genetic basis for absolute pitch. There
have currently been no correlations found involving gender differences. However,
absolute pitch has also been found to be higher among those who are blind from birth,
due to optic nerve hypoplasia. It is also believed to be higher among those with an autism
spectrum disorder or Williams Syndrome. Daniel Levitin explained in This Is Your Brain
On Music how there are even some individuals who have absolute pitch and yet they are
tone deaf. Therefore, just because someone is able to name pitches exactly, does not
necessarily mean that they will be able to sing in tune (Levitin, 2006, pp 188).
Studies have also shown that absolute pitch is less common in the general public
compared to musicians. However, in 1990 Daniel Levitin did a study on the accuracy of
the average person’s memory for music. He chose many non-musicians and had them
sing their favorite song, which had to be a single well-known recording in only one key.
He was surprised to find that the non-musicians sang very close to the absolute pitches of
their songs. Therefore, they were storing absolute pitch information in memory (Levitin,
2006, pp 151-153).
Earlier, it was stated that a small group of people have perfect pitch, in fact, only
an estimated one person in ten thousand. Another small group of the population suffer
from Amusia, or, colloquially, tone-deafness. There are many people all over the world
who believe their horrible singing voice is a result of being “tone deaf”. The term “tonedeaf” is often used to describe people with poor musical skills, when in truth, very few
people in the population actually have this perceptual disorder. People who are truly tonedeaf seem to lack the knowledge and procedures required for mapping pitches and
musical scales (Sacks, 2007, pp 100). Amusia, the technical term for tone deafness,
affects almost 1 out of every 20 people who think they suffer from it, which is a very
small amount of people (Harvard Medical School, 2007). Amusia is also known as the
inability to recognize musical tones or to reproduce them. This disorder can be
congenital, or be acquired sometime later in life, (i.e. brain damage) (MedicineNet.com
2002). There are many different types of Amusia, which are all classified under
“receptive,” “interpretive,” or “performance” Amusia. An example of this disorder is
rhythm deafness, slight or profound, congenital or acquired (Sacks, 2007, pp 99).
There are two basic categories of musical perception, one involving the
recognition of melodies, the other the perception of rhythm or time intervals.
Impairments of melody usually go with right-hemisphere lesions, but representation of
rhythm is much more widespread and robust, involving not only the left hemisphere, but
also many subcortical systems in the basal ganglia, the cerebellum, and other areas
(Sacks, 2007, pp109). Infants at six months can readily detect all rhythmic variations, but
by twelve months their range has narrowed (Sacks, 2007, pp 99). This is the first time
frame during which Amusia or a similar problem can be detected, however, in many
cases, Amusia won’t be diagnosed until later in ones life. Amusia has been described for
centuries, but it is only recently that Amusia has been recognized as a true disease. Even
so, many people are still unaware of the seriousness of this condition, and how it affects
those who suffer from it.
Conclusion:
In researching the topics of pitch, perfect-pitch, and Amusia, this group has
discovered some interesting findings. The development of Perfect-pitch is not yet
entirely understood, although, thus far, it appears to be an interesting blend of genetics,
talent, and environment, with environment playing an especially large role in the
development of perfect-pitch. Factors such as which language one is brought up to
speak, and when or if musical training occurs appear to greatly influence the development
of this skill. Amusia, on the other hand, is a perceptual disorder that is either congenital,
or developed later on in life through brain damage. Thus, the environment has very little
to do with the development of this disorder, unless, of course, the environment was the
cause of the brain damage. The course texts, in particular Levitin’s book This is your
brain on music: The science of a human obsession have helped guide our research as
they are useful resources on how the brain perceives sound and pitch.
Reference List:
Cooke, P. (2007-2008). Pitch. In The New Grove Dictionary of Music (Online). Retrieved
April, 23, 2008, from
http://www.oxfordmusiconline.com.proxy.lib.muohio.edu/subscriber/article/grove
/music/40883?q=pitch&search=quick&pos=1&_start=1#firsthit
Crozier, J. B. (1997). Absolute pitch: practice makes perfect, the earlier the better. Sage,
25(2), 110-119.
Davis, S.F. & Palladino, J.J. (2007). Psychology (5th Edition). Upper Saddle River, NJ:
Prentice-Hall.
Levitin, D.J. (2006). This is your brain on music: The science of human obsession. New
York, NY: Dutton.
Luu, Phan and Posner, Michael. (2003). Anterior cingulate cortex regulation of
sympathetic activity. In Oxford Journals (Online). Retreived March 23, 2008,
from http://brain.oxfordjournals.org/cgi/content/full/126/10/2119.
Sacks, O. W. (2007). Musicophilia: tales of music and the brain. New York, NY: Alfred
A. Knopf.
Saffran, J. R. (2003). Absolute pitch in infancy and adulthood: the role of tonal structure.
Developmental Science, 6(1), 35-43.
Wade-Mathews, M. and Thompson, W. (2002). The Encyclopedia of Music: Instruments
of the Orchestra and the Great Composers. New York, NY: Hermes House.