The “Baby One More Time” hypothesis

I am currently teaching a field course at McGill’s beautiful Gault Nature Reserve on Mt. St. Hilaire in Quebec. Four professors lead the students through a series of modules that investigate various ecological or evolutionary questions, and then the students do their own research projects. During the course of my module, a puzzling phenomenon was exposed in stark relief, which led to the hypothesis I will here describe.

My module investigated whether or not two species of fish (perch and pumpkinseed sunfish) each show resource polymorphism in the lake found on the reserve – that is, to what extent do different individuals specialize on the two main resource types: zooplankton in the open water versus benthic foods in the littoral zone. This topic is of interest because resource polymorphisms of this sort are thought to drive the adaptive radiation of fishes in lakes.

Resource polymorphism is irrelevant to this post except that the data collection set up the conditions that lead to the hypothesis. After catching fish in the lake, we retired to a research lab to process the fish. The “we” was seven students, myself, and the TA – and we established an assembly line for processing fish. The first person measured a series of external traits, the next one removed the gills, the next one counted and measured the gill rakers, the next one removed some muscle tissue for stable isotope analysis and removed the stomach, and then several other students analyzed the stomach contents to infer diets. And so on and so forth again and again and again through a total of about 80 fish.

Catching fish on Lac Hertel.

Needless to say this is all rather tedious – not unlike so many other cases of processing field samples. The typical way to help maintain motivation under such duress is to listen to music. Many of the students had their computers or ipods that included whatever “cool” playlists they had built over the years. First one student would start their playlist and sing enthusiastically along with the songs and perhaps another student or two would join in on one song or another, with the others not knowing many of the songs. Then a different student would start their playlist and sing enthusiastically to each song with the others again not recognize many of them. And so on through a number of students.

Then DJ-TA Felipe Perez-Jvostov took matters into his own hands. He first started playing some of his own favorites, which had roughly the same effect as that explained above. Then for reasons known only to himself, he went to youtube and started playing those trashy pop songs of 10 years ago: Britney Spears (Baby one more time), Christina Aguilera (Genie in a bottle), Backstreet Boys (I want it that way), and so on. The response was instantaneous and dramatic. Within a few notes of the first song (and all subsequent songs), EVERYONE was singing along at the top of their voices, harmonizing, bobbing their heads up and down, generally having a grand time. (Check out the candid video below.) And it isn’t just the current generation. If it had been a bunch of my friends, and someone had broken out Motley Crue (Smokin’ in the boys room) or the Scorpions (Big city nights) or (god forbid) Ratt (Round and round) everyone would have been singing along.

So why is it that everyone played their sophisticated playlists even though no one knew the songs but then when the old trash stuff from their teen years came on everyone knew it and enthusiastically sang along? My hypothesis (and I will grant it probably isn’t original) is this. When young, everyone wants to fit in and so people in a group or social network converge on the same songs (positive frequency dependence in scientific parlance). But as people grow up, many make a conscious effort to stand out of the crowd (negative frequency dependence) and one way this is manifest is by finding less common and more sophisticated music that one then displays to others.

I postulate that this sort of thing is common in the animal world even beyond humans. Juveniles look more similar than adults – and have more similar diets and behaviors – and are often more spatially clustered. So perhaps this shift from conforming to non-conforming is an adaptive ontogenetic shift shared by animals in general. The real question, however, is whether or not it is adaptive – that is, did it evolve because it increased fitness in past environments …

I just stopped writing this post for a few moments to get some whisky and take a pee. In the resulting stream of consciousness, I came up with an adaptive hypothesis – susceptibility to predation. When animals are young (or small), individuals are highly susceptible to predation and so they tend to do things that don’t make them stand out from the crowd. Those that do are toast. When old (or large), however, individuals are less susceptible to predation and so they can afford to stand out. Moreover, doing so often provides mating advantages by getting yourself noticed – the “rare male effect” is one example of this. So perhaps selection really does favor conforming when young but non-conforming when older. Stated more generally, perhaps positive frequency dependence in behavior is more common during juvenile stages and negative frequency dependence is more common during adult stages.

So the next time you feel old and want to recapture the magic of your youth, put on that Vanilla Ice or Motley Crue or Britney Spears again and sing out loud. Everyone will be convinced you are 20 years younger and they will feel 20 years younger too. Although your mating prospects are likely to decrease you will at least be less noticeable to predators. Hit Me Baby One More Time!

Praying Mantis - at the research project site of Natasha, Adam, and Stephanie.

Baby snapping turtle caught by Flavia.

Barred owl.

Garter snake caught at the Gault House.

Pickerel frog - also caught by Flavia.

More photos of these and other critters from the last few days are on my Flikr site: http://www.flickr.com/photos/83007471@N04/