Perfect Pitch: A Central Pattern Generator Leftover?

    In all of my four years here at Bryn Mawr, I have been a part of one of the on-campus a capella groups.  Last year, I had the privilege of being the 'pitch,' or better known as the musical director, of that a capella group. The musical director of the a capella group came to be know as the 'pitch' because one of its main responsibilities is to give the starting notes of each song in rehearsal and in performance.  Right before one of our a capella concerts last year, I realized I had forgotten my pitch pipe, a device which serves as a note or pitch reference used by musicians and 'pitches' of a capella groups.  How could I ever start our songs if I did not have my pitch pipe to refer to for our starting notes?  At that moment, I wished that I had perfect pitch, also referred to as absolute pitch, the unique and rare ability to identify or produce a specific pitch without any external references.  Perfect pitch is a skill demonstrated in less than 1/10,000 of the population and is seemingly difficult if not impossible to learn at an adult age (Bossomaier & Synder 181). Lucky for me that night, the other a capella group we were performing with let me borrow their pitch pipe.
    I first learned of perfect pitch when I met a girl in a choir who claimed that she could distinguish an F from an E from a G or any given tone for that matter just by listening to it. Furthermore, if you asked her to sing a C# without the use a pitch pipe or any type of reference, she could do so! This talent amazed and baffled me. This girl claimed that she was not taught how to identify pitches without reference, it was just something she could do from before she could even remember.  How could someone possess such a specialized and amazing skill?
    While we discussed in class the role and function of central pattern generators, or neural circuits and networks that produce specific outputs, I began to wonder if perfect pitch could somehow be explained in the context of central pattern generators.  I contrasted the presence of perfect pitch in certain individuals with the unlearned egg-ejecting behavior of a newly hatch Cuckoos, a behavior that so clearly exemplifies a central pattern generator. It is this central pattern generator that allows the Cuckoo to naturally and instinctively expel the unhatched host's egg out of the nest. The Cuckoo's egg-ejecting behavior, a clearly highly developed survival mechanism, demonstrates how central pattern generators are integrally shaped by evolution.  Obviously, perfect pitch is not naturally present in the general human population and serves no great survival purpose, however, could there be a link between central pattern generators and this rare skill?  Could perfect pitch be a peripheral left over of a central pattern generators related to speech formation in humans?
    There is still a lot to learn about the science behind perfect pitch but recent research seems to suggest that we are born with the raw equipment to confer perfect pitch.  Jenny Saffran, a psychologist and director of the Infant Learning Laboratory at the University of Wisconsin-Madison, was doing research on the innate tools that help babies acquire language and in that research, she discovered that infants may not have 'dedicated hardware' just for language acquisition. She suggests that infants are not born as blank slates; they instead come with general standard operating equipment that allows for the development of a multitude complex functions such as language acquisition, learning, and even perfect pitch (University Of Wisconsin-Madison 2001).  In other words, the raw apparatus necessary for absolute pitch is available to us all as young babies. In essence, all infants are capable of perfect pitch, though they most likely do not recognize an A as an A or an F# as an F# since they have no concept of notes or scales.
    But why would perfect pitch be a function contained within the standard operating equipment that comes with an infant? Perfect pitch seems to somehow be tied to the learning of speech and language in humans. While no other species match humans in language sophistication, perfect pitch abilities are seen within other animals in their modes of communication.  For example, wolves have been observed to use perfect pitch identification to help in recognizing members of their own pack (Levitin & Rogers 29). In humans, research has shown that the planum temporale, a region of the brain associated with language and speech processing, is consistently larger in the left hemisphere than in the right hemisphere of the brain for individuals exhibiting perfect pitch (Deutsh & Henthorn). While this certainly does not point to a neuroanatomical causation for perfect pitch, it does indicate that perfect pitch is correlated, at least partly, to regions of the brain associated with language processing.
    If perfect pitch seems to be an ability that we are all born with, why then do we lose this ability? Research has come to suggest that the association between perfect pitch and speech may be the very reason this skill so quickly fades out.  It seemingly makes sense that evolutionarily, perfect pitch in other species such as birds or wolves served as great importance in communication and survival. However, in humans, the acquisition of language and speech overcomes the need to keep perfect pitch. Retaining perfect pitch becomes disadvantageous because it puts too much emphasis on the fine details of tone and frequency that it would make it difficult to acquire and comprehend the higher level structures of language. Thus, perfect pitch is inhibited in most individuals within the first year of life with the onset of speech and language acquisition (Bossomaier & Snynder, 181).  Saffran argues that, "If that's [perfect pitch] all we knew, we couldn't generalize any of the sounds we hear. If we only used absolute pitch as adults, we wouldn't understand that 'Happy Birthday' in two different pitches is the same song, or that the word 'cup' spoken by a man and a woman was the same word' (University Of Wisconsin-Madison 2001). This of course is not the case with adults who have retained perfect pitch. The case that Saffran suggests would only be true if we could process only perfect pitches.
    However, there are still those very few that have retained perfect pitch past infancy. Why is that? There has been significant controversy over the nature of perfect pitch because there have been no solid breakthroughs as to why only certain people possess this ability. Some have suggested that genes may play a subtle role in the population possessing perfect pitch since the skill seems more prevalent family clusters, but isolating any genes responsible for perfect pitch will certainly deem difficult (Hall 2002). Other researchers explain that early exposure to music during the critical period in which perfect pitch is still present in our systems is a significant factor that promotes the retention of perfect pitch (Levitin & Rogers 30).  A study done on a group of musicians found that for those that began musical training before the age of 4, 40% of them had perfect pitch. Twenty-seven percept of those who began musical training between the ages of 4 and 6 had perfect pitch, 8% of those who began musical training between 6 and 9 had perfect pitch, 4% of those who began training between 9 and 12 had perfect pitch, and lastly, only 2.7% of those who began training after age 12 had perfect pitch (Deutsch et al 343). There has also been some correlation between perfect pitch and individuals learning tonal languages such as Mandarin, Cantonese, Thai, and Vietnamese (Deutsch et al 343). These languages require a heightened sense of tone and inflection in order to be able to distinguish between lexical meanings. Perfect pitch could possibly have been advantageous in the acquisition of certain languages because of their tonal properties and thus those individuals may display perfect pitch to a certain extent (Deutsch et al 344).
    In the broader picture, the ability to distinguish an F from a C does not hold much survival value for humans as opposed to the egg-ejecting behavior or Cuckoos. While perfect pitch may not be based on a central pattern generator in humans, perhaps it is in other species that heavily rely on pitch recognition as a means of survival. With evolution, however, the perfect pitch central pattern generator could have changed and developed into our complex neural circuit which better suits our need for our primary form of communication, language and speech. Thus, maybe, just maybe, perfect pitch is a peripheral yet specialized skill indicative of the evolution of central pattern generators.  
 

References

Bossomaier, Terry, and Allan Snyder. "Absolute Pitch Accessible to Everyone by Turning off Part of the Brain?" Organised Sound 2 (2004): 181-89. Web. 27 Mar. 2010. <http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=250460>.

Deutsch, Diana, Trevor Henthorn, and Mark Dolson. "Absolute Pitch, Speech, and Tone Language: Some Experiments Anda Proposed Framework." Music Perception 21.3 (2004): 339-355. Web. 27 Mar. 2010. <http://caliber.ucpress.net/doi/abs/10.1525/mp.2004.21.3.339>.

Hall, Carl T. "Noting the Perfect Pitch -- Rare Musical Ability to Distinguish Sounds by Ear Could Be Genetic." Noting the Perfect Pitch. 14 Jan. 2002. Web. 27 Mar. 2010. <http://www.wsf.org/family/news/sfchronicle.htm>.

Levitin, Daniel J., and Susan E. Rogers. "Absolute Pitch: Perception, Coding, and Controversies." TRENDS in Cognitive Sciences 9.1 (2005): 26-33. Science Direct. Web. 27 Mar. 2010. <http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VH9-4DXTHVD-1&_user=400777&_coverDate=01%2F01%2F2005&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1280733668&_rerunOrigin=scholar.google&_acct=C000018819&_version=1&_urlVersion=0&_userid=400777&md5=76d4a5f8cacc79411aef1953e37ddd5f>.

University Of Wisconsin-Madison. "Born With The Perfect Pitch?." ScienceDaily 27 February 2001. 4 April 2010 <http://www.sciencedaily.com_ /releases/2001/02/010222074848.htm>.