Tuesday, January 27, 2009

Do newborn infants have a sense of rhythm?

[Report related to PNAS Early Edition]

It might look somewhat disturbing, but the picture that accompanies this entry is a snapshot of a two day old baby that is healthy and sound asleep! She is one of fourteen newborns that participated in a recent listening experiment, a collaboration between the Institute for Psychology of the Hungarian Academy of Sciences and our research group at the University of Amsterdam in the Netherlands. In this project we are interested in how newborn infants perceive the musical world around them and in how far certain musical skills are innate.

We know that newborn infants are sensitive to a variety of sounds. But what do they factually hear? Can they make sense of the musical world around them? Do they have a sense of rhythm, arguably one of the fundaments of music?

To study this, we collaborated with a research group in Budapest, Hungary lead by István Winkler, a specialist in auditory perception and one of the pioneers in measuring brain activity in neonates.

Since the start of this European research project (named EmCAP) we talked a lot about how we could take advantage of existing theories in music cognition to study auditory perception in newborn infants, and how to probe their (potential) sense of rhythm. After many pilot studies, and resolving quite a few methodological issues that come with doing experiments with neonates, in the end we opted to use a simple, regular rock rhythm, consisting of hi-hat, snare, and bass drum (see below). We made several variants of this rock rhythm by omitting strokes on non-significant metrical positions (i.e. non-syncopated rhythms in music theoretical terms). We then inserted, once in a while, a 'deviant' segment: the same rhythm but with a missing ‘downbeat’ (i.e. a syncopated rhythm). The result sounded like this [click on the play button; to stop, click again]:

Since it is quite difficult to observe behavioral reactions in newborns a small number of electrodes were carefully glued to the scalp and face of the newborns to be able to measure their electrical brain signals (see photo). N.B. The baby’s were fed just before the measurements with their mother being present during the whole session that lasted twenty minutes.

What did the experiment reveal? Well, shortly after each ‘deviant’ segment began, the babies' brains produced an electrical response indicating that they had expected to hear the downbeat but had not. As such we could show that newborn infants can detect the beat in music (The results will be published this week in PNAS Early Edition).

What are the potential implications of these findings? For me, one of the most important realizations is that a cognitive skill called beat induction, which most of us think of as trivial (e.g., being able to tap your foot to the beat), is active so early in life. It can be seen as additional support for the idea that, beat perception contributed to the origins of music since it enabling such actions as clapping, making music together and dancing to a rhythm. Next to being music-specific, beat induction is also considered to be uniquely human. Even our closest evolutionary relatives, such as the chimpanzee and bonobo, do not synchronize their behavior to rhythmic sounds. This makes the topic of beat induction a fundamental issue in current music cognition research (see, e.g., Patel, 2008:402).

Furthermore, the results challenge some earlier assumptions that beat induction is learned in the first few months of life, for example by parents rocking the infant. Our study suggests that beat perception must be either innate or learned in the womb (as the auditory system is at least partly functional as of approximately three month before birth).

Finally, it should be noted that the auditory capabilities underlying beat induction are also necessary for bootstrapping communication by sounds, allowing infants to adapt to the rhythm of the caretaker’s speech and to find out when to respond to it or to interject their own vocalization. Therefore, although these results are compatible with the notion of the genetic origin of music in humans, they do not provide the final answer in this longstanding debate.

ResearchBlogging.orgIstván Winkler, Gábor P. Háden, Olivia Ladinig, István Sziller, Henkjan Honing (2009). Newborn infants detect the beat in music. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0809035106

Wednesday, January 07, 2009

Hoe was het Spinozadebat? [Dutch]

This is a short entry with a video impression of the Spinoza te Paard lecture series on recent developments in science, aimed at a general audience. The full broadcast can be viewed at spinozadebat gemist.