Scientists in Singapore have discovered that sugar is the key component of a substance produced by injured fish to warn other fish of danger. The researchers say their findings could have implications for how fear is generated - and might possibly be controlled - in humans.
The zebrafish in the video is being exposed to a slow release of pure water through the hose at the top of its tank. The fish shows no reaction. But when scientists exchange the pure water with sugary water the fish's reaction is significant.