Their stock splits aren't the main reason for these stocks' huge gains this year.Everyone knows that slicing a pizza into six or eight pieces doesn't provide more food than slicing it into four pieces. Such slicing is basically what stock splits do.However, stock splits can sometimes attract new investors who otherwise wouldn't have bought the stock. And this can drive the share price higher. We've perhaps seen this phenomenon in effect this year with several high-profile stock splits. Here are the three be ...