They believed that if the animals saw their shadows, winter would continue, and so they went back to sleep.

CNN: Shadows aren't just for groundhogs

If the animals saw their shadows, winter would go on for another six weeks, and they could go back to sleep, according to the tradition.

CNN: Warm temps are near, Punxsutawney Phil predicts

Winter, city life (with the concomitant shadows cast by tall buildings) and dark skin in dark climates all reduce this action.

ECONOMIST: Schizophrenia: Let the sun shine in | The