Flocking together

The latest research from Italy on the flocking behaviour of birds seems to pile on the evidence against trends starting with a handful of "Influentials".

As I've mentioned before, the recent marketing wisdom has been that a handful of trend-setting individuals are disproportionately responsible for the "viral" dissemination, and therefore success, of new products and ideas. Malcolm Gladwell popularised this notion in The Tipping Point, writing that "the success of any kind of social epidemic is heavily dependent on the involvement of people with a particular and rare set of social skills". These people are Connectors, Mavens and Salesmen. Get the right handful onside, the theory goes, and you've got a hit.

Research by Duncan Watts popularised in 2007 began to knock holes in this theory, showing that popularity and memetic dissemination were a peer effect rather being led by this handful of "influentials", and his later research confirmed this view.  Today, under the heading "Trust in Peers Trumps the A-List", Steve Rubel at Micropersuasion points to yet another set of research from Pollara seeming to confirm that view that people take their lead from their immediate peers, not a leadership of influential individuals. All that marketing effort to target these imaginary "influential" visionaries seems, increasingly, to have been wasted.

My own eye was caught last week by research from Andrea Cavagna at INFM in Italy which seems to have cracked for the first time the question of how individual birds know where to go when flocking. As regular readers will know I am too ignorant of both experimental biology and statistical analysis to usefully summarise such a piece of research, but for what it's worth what Andrea's team seems to me to have found is that starlings flock not by interacting with the birds within a certain proximity but by interacting with a fixed number of the birds that happen to be around them.

"By measuring the anisotropic structure of birds within the flock we were able to track the interaction among the birds. At variance with previous models and theories, we found that the strength of the interaction binding two individuals does not decay proportionally to the metric distance between them, as previously assumed, but rather to the topological distance. An example may clarify this result: whenever we take the bus, we do not measure the distance between two stops in meters, or kilometres (metric distance), but rather in number of stops (topological distance). Birds do something similar: they measure the distance in units of individuals, not meters. This implies that each bird interacts with a fixed number of neighbours, rather than interacting with all neighbours within a fixed metric distance, as assumed by all current models. In particular, we discovered that each bird always interacts with 6-7 neighbours, independently of the metric distance of these neighbours."

Here's a summary of the research.

Two things struck me as interesting and relevant about this.

First, that birds, when flocking, make decisions relative to a fixed number of individuals around them, irrespective of their distance from the other birds. Decisions on how to move depend on a fluctuating set, but set number, of peers. If (and, granted, it's a big "if") people behave in a similar way when deciding, for example, what music to buy this would support the view that peer effects are paramount in making decisions.

The second thing that struck me was how potentially similar to the Dunbar Number this research tales us. If animals' flocking behaviour requires them to keep in mind a similar or even the same number of individuals as the Dunbar Number suggests they are able to maintain as a social circle...then we have at least a correlation between friendship groups and decision-making.

I asked Andrea about this possibility and he said he wasn't sure there was a connection. Fair enough - after all, I'm just speculating. But it would be an interesting coincidence if people took their buying cues from, say, 148 peers.