PARIS(AFP).- Scientists believe Leonardo da Vinci's super-fast eye may have helped him catch the enigmatic magic of Mona Lisa's smile.

This superhuman trait, which top tennis and baseball players may also share, allowed the Renaissance master to capture accurately minute, fleeting expressions and even birds and dragonflies in flight.

Art historians have long talked of Leonardo's "quick eye", but David S Thaler of Switzerland's University of Basel has tried to gauge it in a new study published Thursday alongside another paper showing how he gave his drawings and paintings uncanny emotional depth.

Professor Thaler's research turns on how Leonardo's eye was so keen he managed to spot that the front and back wings of a dragonfly are out of synch -- a discovery which took slow-motion photography to prove four centuries later.

The artist, who lived from 1452 to 1519, sketched how when a dragonfly's front wings are raised, the hind ones are lowered, something that was a blur to Thaler and to his colleagues when they tried to observe the difference themselves.

Thaler told AFP that this gift to see what few humans can may be the secret of Leonardo's most famous painting.

"Mona Lisa's smile is so enigmatic because it represents the moment of breaking into a smile. And Leonardo's quick eye captured that and held it," he said.