Hi, the tough part is in deciding whether something you are observing is actually "form" or just a random series of events. If you are playing roulette and red comes up twice in a row, is red "in form" now? You know the answer is "no" because of statistics and probabilities. But with racing many people draw a different conclusion. A horse has two good races in a row and he's "in form." But how do you KNOW it's form and not just a statistical coincidence?

Well, the way that you determine that is by actually studying hundreds of horses. If such a thing as "form" exists, then you should be able to see it by using sequential comparisons. A performance in a given race should be closer to a performance in his previous race than to his career average. (You have to be VERY careful when doing this, or you will see CLASS ladder artifacts and mistake them for form, or you will see lifecycle effects at the beginning and end of careers.) But I've done study after study and never seen a statistically-significant relationship between adjacent performances. In every study, a horses adjacent performance look exactly like what you would expect from random performance around their average talent level, given their standard deviation. Thus my conclusion, at least with current evidence, that form doesn't exist as a predictive factor.
Cheers