“Five years ago, the main view of beat perception and beat induction was that it is something human-specific, something only humans can do. Then there was Snowball, the dancing cockatoo, that seems to be able to synchronize with the rhythm. Interestingly enough, they cannot train primates to synchronize to the beat. Why can other primates not do this? One of the possibilities is that the cognitive system is able to perceive the beats, but it is not that well integrated with the motor system. In that case, we might be able to find something using EEG-techniques which we will not be able to find using behavioral measures.”

“In my research I try to find a minimal stimulus set to induce a beat. Something that you can get into, get synchronized with and something that is at the same time of minimal complexity. The rationale behind finding this stimulus set is that we want to be able to test groups that are not really good at giving behavioral responses such as  infants and different kinds of animals.”

Newborn babies

“As a PhD-student, I worked on a project where we tested newborn infants, still in the hospital. This would be hard to do in the Netherlands, because women give birth much more often at home than in hospitals. In Hungary it is customary to give birth in a hospital, so we have a time window of a couple of days to test newborn babies. We tested a couple of really basic abilities in newborns. We chose the abilities that in our opinion underlie music perception. We did a study on relative pitch: how you can extract sizes of pitch steps when the absolute pitch varies or is randomized over a window of different pitches. It seems that babies can do this. We also had a an experiment on timbre-independent pitch perception: how you can recognize a middle C on both a piano and flute.”

“We had an experiment where we tested adults in meter perception. Meter is just beats organized in a hierarchical fashion. Most people are able to perceive meter when paying attention and we tried to test whether their brains can automatically do that. It seems they can. We also did a simplified version of this experiment with the babies, only testing a simple beat. It seems that babies, just as adults, are able to extract this beat. The stimulus set was really fun to work with, because it was something like a 4-4 rock ‘n roll rhythm. We could always hear what the subject was hearing. The babies would look like they were sleeping, but from the brain it seems that they were rocking hard!”

“What I am doing now in Amsterdam, is basically the replication of the baby experiment in monkeys. We want to see how the monkeys perform with the stimulus set from which babies were able to extract the beat. It turns out that monkeys were not able to extract the beat. But they actually do something really interesting. The stimulus set consists of a 1.2 second long sequence. If you know it is a sequence and focus a lot, you can recognize the sequence, but for all we know, automatic processes do not work for such a long time interval. It turns out that the monkey seems to extract this whole pattern. Not the beat, not the gap in the pattern, but the whole sequence and they just treat it as a whole. This would be much more memory related than music related, but really merits further investigation.”

Mismatch

“In the EEG signal, we are looking for a component which is called the mismatch negativity (MMN). This is a bump in the averaged EEG signal in response to events that violate some auditory regularity, something different from what has been expected by the auditory system. Basically with MMN you can test whether some kind of rule has been extracted by the auditory system: if you see an MMN when the rule is violated in the auditory signal, you can infer that the brain is using the rule. Of course it is very important to use good controls to make sure that the brain is hypothesizing exactly this rule. What we did is looking at omissions on different positions of the beat to see if they resulted in MMN signals.”

“Based on these results, you cannot say that monkeys cannot perceive beat, but you should be a bit more reserved: it seems that they cannot do this in this task. This result is consistent with the vocal learning theory of Aniruddh Patel, which says that beat induction is a privilege or a necessary skill for vocal learning species like songbirds, humans, certain kinds of seals and whales that learn their vocal repertoire and have a kind of intricate and full social life.”

You said that auditory perception is based on the brain knowing what stimulus to expect, would you say that that is in general the role of a brain?

“I would say that this is really the function of the auditory system or in the general sense the function of the brain. The brain is a prediction machine, it tries to predict what comes and if something unexpected comes up, it just deals with it. That is the whole point of having a brain: that you can know what is normal and if something abnormal comes in, then you can deal with the situation.”

“I had some really nice debates with a friend of mine who is into Gibsonian direct perception. In a sense you get the feeling: yes, this approach is right, it has a really strong ecological validity. But then you ask: “ok, how can I test this? Even if action and perception are a coupled system, it still has parts. Maybe I am not to come up with the best theory of automobiles by looking at either the engine, the wheels or the suspension system, but I am going to learn something about cars.:

“This is also the kind of logic behind what we did with the monkeys. If we were completely theory-driven, then we would say: if monkeys cannot do it behaviorally, then they just cannot do it. But it might still be the case that they can perceive it, they just do not act on it. It can still be the case that if we motivated them better we would get different results. These were actually passive experiments, the monkey was basically just sitting there.”

Dolphins and seals

“In the future I would love to do more comparative research. I would like to get into contact with people who are working with birds, with marine mammals, dolphins or seals and have a collaboration on these kind of beat things. I want to go after the vocal-learning hypothesis in a really methodological way. In order to do that, one has to come up with an even better paradigm. Like I was saying at the beginning: one would have to have a good stimulus set that induces beat. My big dream is to give a general theory of how people perceive different sequences and patterns in time. Be it something linguistic, be it something in music, just how people do deal with patterns from the millisecond timescale to really larger timescales. On one side drifting to neurobiology of timing and on the other side towards circadian rhythms, memorizing structure and how people have structure in their perception and in their lives.”