Lévy Flight Strategies in Human Mental Searches

When: Thursday, February 28, 2013 at 1:30 pm
Where: DA 5th fl
Speaker: Andrea Baronchelli
Organization: MoBS, Northeastern University
Sponsor: Joint Network Seminar

Lévy flights are a special class of random walk whose step
lengths follow a power-law tailed distribution. They represent the
best strategy that can be adopted by a random searcher looking for a
target in an unknown environment, and have have been widely observed in
many natural contexts. Here we report empirical evidence that Lévy
flights describe not only movement patterns in real space, but also
searches performed by humans in non-physical spaces during online
games. The power-law scaling can be measured over several decades and
represents the best supported observation of Lévy flights in nature
reported so far. We show that the histogram describing single
individual exponents is well peaked, pointing out the existence of an
almost universal behaviour. Surprisingly, a simple model reveals that
the observed strategies (i.e., Lévy flight exponents) are furthermore
nearly optimal. We rationalize these findings through a simple
evolutionary process that is able to account for the empirical
measurements by assuming that the reproductive fitness of a searcher is
proportional to her search ability. Our results generalize previous
research, showing that humans share with the other animals universal
patterns in general searching processes, and raise fundamental issues
in cognitive, behavioural and evolutionary sciences.