Tuesday, April 9

Monkey Funk (or lack thereof)

Sea lion is first non-human animal to keep a beat

Ronan is the first known non-human mammal successfully trained to bob her head in time with a metronome-like sound — and then to apply her new skill to tempos and music she had not previously heard, according to researchers at the Long Marine Laboratory at the University of California, Santa Cruz.

This is the biggest news in auditory (or at least musical) animal behavior, right now. Make sure you get to the bottom of the linked page where you will be rewarded with video evidence. It will be worth your while.

Reminds me of a similar, recent article featuring rhesus macaques. I was quite surprised to find that I had not previously written a post about said article. I won't let it by me a second time.

In this article, the authors describe results which suggest that macaques can detect rhythmic perception, but not beat induction (according to the earlier study, sea lions are the only mammal other than humans that can do both). The theory that there is a distinction between these two faculties is know as the dissociation hypothesis.

None of these terms are intuitively obvious. Beat induction is the ability to detect regularity of beats in a rhythm. It is what gives us our ability to tap our foot along with the beat in a song. Rhythmic perception merely refers to the ability to tell that some specific amount of time has passed. This sort of timing work has been studied extensively in many animal species, and it is well known that pretty much all mammals can time intervals. In fact, I have myself done some work demonstrating rhesus macaques' flexibility in timing intervals (Diapadion et al, unpublished results or something).

There is a major drawback to this monkey study: there is no behavioral data. It is entirely EEG. In many ways, I prefer EEG to fMRI or electrophysiology for brain imaging. EEG takes a distributed look at the activity of billions of neurons, unlike eletrophysiology, where you isolate signals from single neurons and pretend that the entire brain region surrounding acts the same way. fMRI also takes a distributed look at brain activity; in fact it is often more accurate than EEG. Unfortunately you can't put monkey into a MRI scanner unless the monkey has been knocked unconscious. You have to stay still in the scanner to get good data, and monkeys, well, they're not so good at that, ever.

fMRI is also superior to EEG because fMRI allows you to see deep into the brain, whereas EEG only lets you look at surface areas because it is on the surface of the skull that you place the EEG electrodes. There might be something going on deep in the auditory cortices that the authors' EEG findings are missing. Which is why it would be nice to see some results from additional metrics. Practically speaking, I don't believe it is likely that the authors are mistaken; the primate literature supports their hypothesis.

In the sea lion video, the speaker suggests that beat keeping may be far more widespread in the animal kingdom than previously thought. No, probably not. This EEG study suggests that monkeys are totally incapable of beat induction, and it stands to reason (and evidence) that this holds for other primates. As it stands, convergent evolution is the most likely explanation.

Honing, H., Merchant, H., Háden, G., Prado, L., & Bartolo, R. (2012). Rhesus Monkeys (Macaca mulatta) Detect Rhythmic Groups in Music, but Not the Beat PLoS ONE, 7 (12) DOI: 10.1371/journal.pone.0051369

1 comment:

  1. Does this mean Sea Lion choruses (like from the Oregon coast) will soon be featured on some prominent hip hop singles?