During the experiment the scientists put three electrodes into the brains of the rats and used them to train them.
One electrode makes the rats feel pleased when they detecte the smell of a human, so finding people actually makes the rats happier.
Bomb detectors too
The second creates a signal when the rat smells what it is looking for and the third helps it plan how to get there.
A report in New Scientist magazine revealed the scientists hope to have the scheme working in nine months, and adds that the rats may be able to find bombs or explosives too.