The rat pack gets the job done

Rats work well in teams, it seems. A new study suggests rodent groups outperform individuals in searching for a target, even when they have limited ability to communicate or share information.

Researchers in Europe report this discovery after tweaking the classic “rat in a maze” experiment to make it “rats in a maze”.

They used automated video tracking to follow individuals (all marked with bright colours) as they simultaneously explored their environment, revealing that rats use simple behavioural rules to achieve superior search performances in groups.

“Using a group of rats to model collective problem solving has pinpointed basic mechanisms employed by rodents and lent insight into underlying rules of how individuals enhance search performance by being in groups,” says Tamás Vicsek, from Hungary’s Eötvös Loránd University, senior author of a paper in the journal Cell Biology.

And those insights may provide “the means of directly inspiring algorithms for collective search applications”, adds Máté Nagy, who led the project while at Germany’s Max Planck Institute of Animal Behaviour.

For the study, the team built a relatively large and complex maze with 16 endpoints. Its structure meant rats could only see others in very close proximity. Each endpoint was equipped with a water dispenser, but only one of these provided a water reward.

In the search task, rats could locate the water alone or in groups of eight. They were tracked and their individual trajectories reconstructed via automated tracking software, which allowed for deciphering the underlying characteristics of search behaviour.

Rats in a group were more successful. When Nagy and colleagues took a close look at the decisions made at the maze junctions, they found that the actions of those in groups could be boiled down to simple rules: go down unexplored paths but follow other rats.

In order to confirm the generality of these rules, they carried out computational modelling with large numbers of simulations to show the search performance result of different combinations of these simple rules.

They found that when searching as a group, individuals performed best if they had the right balance between solo exploration and following others.

Both extremes – ignoring others completely or following others too much – resulted in lower performance for the group as a whole, as well as for individuals in the long run.