It's hard enough getting four people to agree on a rental video. Several hundred ants, however, pick the best among possible nest sites with ease. Each small act of an individual ant ensures that, together, the colony makes the right move.

Laboratory colonies of the European ant, Leptothorax albipennis, were made homeless by Stephen Pratt, of the University of Bath, UK. Pratt triggered migration by dismantling the ants' artificial nest, and giving them a choice of new homes.

When an ant scout finds a potential nest site she inspects it. The ants, who nest in rock crevices in the wild, prefer wide, dark crannies with small entrances. The scout returns to the old nest, and leads another ant there in a nose-to-tail procession. The new recruit forms a second opinion, returns home to lead a third, and so on.

But an ant thinks twice before she recruits the next advocate; the less she likes her potential new home, the longer she waits, found Pratt. "The ants are taking a sort of poll of their nest mates," he told the meeting of the Animal Behavior Society in Corvallis, Oregon. Desirable residences attract recruits quickly, while dumps' popularity withers.

If an ant arrives at a new site and finds many nest mates already there, her behaviour switches. Instead of leading new recruits, she starts to move belongings: carrying ants, larvae and eggs from old to new sites. A point seems to be reached when the colony's collective mind is made up, and migration accelerates.

Many individuals following a few simple rules result in complex and powerful behaviour. "You don't need a complex set of rules for patterns to emerge," says Jennifer Fewell, who studies ants at Arizona State University in Tempe. Brains, embryonic development and ecosystems show similar complex 'emergent' properties from simple interactions, says Fewell.

Such patterns may be an inevitable result of the interactions, rather than being favoured by natural selection, she says - studying them requires a different way of thinking. "We've looked at things from the perspective of evolution, rather than how the pattern gets there in the first place," says Fewell.

The idea that lots of little brains can solve problems better than a big one has captured the imagination of computer scientists. "There's an entire field developing based on ant algorithms," says Pratt. This tackles complex problems such as designing distribution networks.

Robotics engineers also foresee that groups of many simple machines could be adaptable and robust, as each individual is expendable.