Metrical Categories in Infancy and Adulthood

Erin E. Hannon and Sandra E. Trehub

The study asks whether the ability to detect structure-violating alterations to a rhythmic pattern is learned or innate.

North American music uses simple meters based on groupings of two, three or four beats. When North American musicians conceive of complex meters, we usually think in terms of compounded simple ones. To count in 11/8, we might think "3 + 3 + 3 + 2."

Bulgarian and Macedonian adults grow up with music in complex meters, and feel these meters as complete units rather than composites of simple meters. An example of Bulgarian 11/8 (Kopanitsa): http://www.youtube.com/watch?v=Giz3glVPm-I

MethodFam: familiarization stimulusSP: structure-preserving alterationSV: structure-violating alteration

Grey dots show the drum accompaniment to the musical example. Alterations are in the form of added notes, shown by dashed lines.

The structure violation in the simple-meter example is an extra eighth note added to the bar of 4/4 time.

The structure violation in the complex-meter example is an extra eighth note added to the bar of 7/8 time.

FindingsThe top panel shows mean dissimilarity judgments of North American adults. The middle panel shows the same for Bulgarian and Macedonian adults. The bottom panel shows infants' mean looking times. Simple-meter results are on the left, and complex-meter results are on the right.

North American adults had no difficulty telling the difference between structure-preserving and structure-violating alterations in simple meters. However, they performed poorly in complex meters.

Unsurprisingly, Bulgarian and Macedonian adults performed almost identically on tests with simple and complex meters.

Against expectation, however, North American infants performed more like Bulgarian and Macedonian adults than like North American adults.

AnalysisOne would naively guess that the ability to parse simple meters is learned early in life, and that we learn more complex metrical schemes by compounding simpler ones. The experiment contradicts this assumption. It appears that North Americans learn a bias toward simple meters — or perhaps we forget how to parse complex meters.

Do infants process rhythms differently than adults? Do they just hear strings of beats without hierarchical organization? Probably not. Infants demonstrate the ability to parse other forms of musical organization. For example, they can detect:

• subtle changes in duration and tempo• isochronous (steady) versus nonisochronous

(unsteady) tone patterns• auditory patterns generalized on the basis of

rhythmic structure• unique rhythms on the basis of implied metrical

structure

Discussion QuestionsAre adult biases in temporal pattern processing learned during musical enculturation?

Is there a relationship between our innate ability to parse variations to metrical schemes and our ability to pull words and prosody from the speech stream, even though everyone speaks differently?

How do we reorganize our temporal pattern processing tools? How does exposure to music "reprogram" us? More generally, how do we figure out which distinctions meaningful in our culture?

If I play a lot of Bulgarian music at home, will Milo be able to groove to 11/8, or does he need to hear it everywhere?