0.7 Music, biological evolution, and the brain  (Page 11/30)

A notable similarity between tonality and linguistic syntax is the existence of abstract structural categories that organize sequences of events. In tonality, for example, structural categories such as the tonic (the most stable pitch in the tonal hierarchy) or leading tone (an unstable pitch in the hierarchy) can be realized by any pitch. For example, the pitch B4 (493.9 Hz) can serve as either the tonic or leading tone of a melody, depending on prevailing tonal hierarchy. Language also has abstract structural categories, such as grammatical subject and object, that can be realized by a variety of words.

In both domains, abstract categories play an important role in mental processes involved in sequence comprehension. To take one example, in processing a melody one may expect a tonic as the next note (vs. expecting a specific tone frequency in Hz), and in processing language, it is possible to expect a grammatical object as the next word (vs. expecting a particular word) (Huron, 2006; Gibson, 2006). To take another example, in both domains incoming categories vary in how easy they are to integrate into the existing structural representation of the sequence (Bigand et al., 2003; Koelsch et al., 2007; Gibson, 1998; Levy, 2008). According to the SSIRH, difficult structural integrations in both domains draw on a shared pool of limited neural resources (see Patel, in press (a), for details).

To recap, tonality involves domain-specific knowledge : the long-term knowledge of tonal hierarchies, for example, is specific to music. Yet online processing of tonal relations appears to share mechanisms with language processing, possibly because tonality, like linguistic syntax, deals in abstract categories that are processed in terms of hierarchical structures. The deeper lesson, in terms of exploring links between music cognition and other domains, is the importance of distinguishing domain-specific representations from non-domain-specific processing mechanisms. Indeed, in the case of tonality, non domain-specific mechanisms may be important not only for online processing, but also for the acquisition of knowledge. According to Krumhansl and Cuddy (in press), two psychological principles underlie the development of tonal hierarchies in the mind of a listener: the use of cognitive “reference points” and mechanisms of statistical learning. They note that neither principle is unique to music, but that the application of these principles to music results in domain-specific musical knowledge. In other words, tonal music may represent a case of the mind creating domain-specific knowledge via non domain-specific processes (cf. McMullen and Saffran, 2004).

3.2 entrainment to a musical beat: connections to vocal learning

In every human culture there is some form of music with a periodic beat pattern, to which people synchronize their rhythmic movements, e.g., in dance (Nettl, 2000). Periodic beat patterns need not be based on an isochronous (metronomic) pulse. For example, Balkan rhythms can have temporally-repeating cycles ofbeats, with each cycle having asymmetric time intervals between beats (cf. Patel, 2008: 98). Musical beat perception and synchronization (BPS) is an example of the entrainment of rhythmic action to rhythmic sound. BPS does not appear to be an offshoot of language. Language has rich rhythmic structure and can involve tight temporal coordination (e.g., in conversational turn-taking), but does not have temporally periodic beats and does not elicit periodic rhythmic movement from listeners (Patel, 2008, Ch. 3). Notably, BPS (e.g., head bobbing and foot tapping to music) emerges without any special instruction in humans, which makes it an intriguing topic of study from the standpoint of evolutionary biology. Has the human brain been specifically shaped to support this ability?