A shorter sells without even owning the stock. He keeps selling and then when the Volume becomes flat he starts to hit the bid or buys at the bid price trying to make the price come down while covering his shares that he has already sold. The more panic he can create from week kneed investors and the more spread he can create from his sell price the more money he puts in his pocket!! Your money.

If nobody sells and the share price goes up over what he has sold at already the more money it costs him to cover the stocks he already sold at without actually owning any shares. 

Hope this helps your average investor looking for the upside.

just remember when they start asking if your on medication it's because it's something they don't want to hear or that will help them recapture their shares to cover what they have already sold.

GLTA Hope this helps.