He's trying to lure a call by using such strange behavior that his opponent will become suspicious.
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While this may look similar to a tell discussed in the category of tells called Strong Means Weak, it isn't. In the former case the bettor grabbed for the chips while the opponent was passing, acting strong to keep him from reconsidering. Remember, players with winning hands will give an opponent every opportunity to call. What you see in this example is a ploy. The opponent hasn't even decided what to do yet. The bettor's hands remain outstretched while he awaits that decision. When you see a pot-snatching mannerism this blatant, you can be pretty sure the bettor wants his actions to appear bizarre. He figures that will earn him a call Ñ and it usually does.