Tuesday, April 02, 2013

Confirmation of vocal learning hypothesis instead of falsification?

It was recently shown that rhythmic entrainment, long considered a human-specific mechanism, can be demonstrated in a select group of bird species, and, somewhat surprisingly, not in more closely related species such as nonhuman primates. This observation supports the vocal learning and synchronization hypothesis (Patel, 2006) that suggests that rhythmic entrainment is a by-product of the vocal learning mechanisms that are shared by several bird and mammal species, including humans, but that are only weakly developed, or missing entirely, in nonhuman primates. However, since no evidence of rhythmic entrainment was found in many vocal learners (including dolphins, seals, and songbirds), vocal learning may be necessary, but not sufficient for beat induction – the cognitive mechanism that supports the perception of a regular pulse from a varying rhythm.



Nevertheless, on April Fool's Day another piece of evidence – according to the authors falsifying the above mentioned hypothesis – was published in the Journal of Comparative Psychology reporting on a sea lion (Zalophus californianus) that was able to learn to entrain to the beat of music (Think of Everybody of the Backstreet Boys and Boogie Wonderland of Earth, Wind and Fire).

I have to admit that my library does not have access to the journal, so I have not been able to read the full paper as yet. But the video (included above) mentions a peculiar detail: the authors claim Sea Lions not to be vocal learners, and hence to have 'falsified' the above mentioned vocal learning and synchronization hypothesis. However, in how far pinnipeds have some level of vocal mimicking capabilities is still unclear. This combined with the fact that 'absence of evidence is no evidence of absence' (cf. Fitch [and comments below]), it seems again too early to tell...

ResearchBlogging.orgCook, P., Rouse, A., Wilson, M., & Reichmuth, C. (2013). A California Sea Lion (Zalophus californianus) Can Keep the Beat: Motor Entrainment to Rhythmic Auditory Stimuli in a Non Vocal Mimic. Journal of Comparative Psychology DOI: 10.1037/a0032345

ResearchBlogging.orgArnason, U., Gullberg, A., Janke, A., Kullberg, M., Lehman, N., Petrov, E., & Väinölä, R. (2006). Pinniped phylogeny and a new hypothesis for their origin and dispersal Molecular Phylogenetics and Evolution, 41 (2), 345-354 DOI: 10.1016/j.ympev.2006.05.022

3 comments:

TH said...

Very interesting study. I unfortunately don't have access to the journal either, but was wondering about the "status" of sea lions as vocal learners, as well. My recollection was the same as yours, that they would be among the vocal learners. However, according to Adena Schachner's paper (DOI 10.1016/j.cub.2009.03.061), seals are listed as vocal mimickers while sea lions are listed in the non-vm column (Figure 2). In their study, among other things, they looked at a bunch of YouTube videos of animals "dancing", and analysed phase and period entrainment. They found relatively many sea lion videos (30), but there was no evidence of entrainment in any of them.

At a quick glance, I didn't find a reference for where their classification of seals as vocal learners and sea lions as not was coming from. Perhaps there is a difference within the Pinnipeds, Fitch also mentions only seals as examples of entrainers in that blog post you linked.

Henkjan Honing said...

Thanks for the comment, Tommi. Indeed, while harbour seals ("true" seals) are clearly vocal learners, there is no solid evidence that Sea Lions (eared seals) are (so Tecumseh Fitch ensured me :-)

Hoever, there is even more excitement going on... see next post...

Henkjan Honing said...

My mailbox is filling up with emails of e.g. Tecumseh Fitch, Ani Patel, Peter Cook and others -- I hope they'll join the forum here :-) If not, I will summarize some of it in a future post.

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