I would guess that every experienced poker player is familiar with the following situation: In the middle of a hand, an opponent - who is reasonably well-known to you - does something. It doesn't really matter what he does; maybe he bets, raises, check-raises, or even just calls. And at that moment, you feel sure - absolutely sure - that you know what hand he has.

OK, you say, so what if we have some hand-reading skills? Almost all decent poker players do. What's the big deal? Well, the big deal is this: This particular case is peculiar because you have absolutely no idea why you know. You just have a strong hunch and are sure it is right.

If you are playing live, there is a lot of baggage in the situation in the form of body language, tells, and so on, and you are very likely picking up on something along these lines. However, when you play online, the environment is much "cleaner." The only non-poker clue you have is the handle (an alias used for playing) of your opponent. However, anyone who allows himself to be seduced into thinking that players who choose to call themselves "TotallyOnTilt" or "RockofGibraltar" are giving away their game plan is not showing any great sophistication. Actually, all you have to base your hunch on are the betting patterns and previous play of your opponent. Occasionally, he may have just sat down at the table, and you don't even have that.

In his fascinating book Blink, Malcolm Gladwell explores just this phenomenon - although not in a poker context. He cites numerous examples of how someone's instant impression of a situation often turns out to be completely accurate - even though he is unable to articulate why this is the case or how he arrived at his judgment. Usually, it was what we like to refer to as gut instinct; it just "felt right." Of course, when the situations are analyzed carefully, it is often the case that it is possible to pick out a clear line of logical reasoning that leads to the (correct) conclusion. Doubtless, on some higher level, our brain has processed and analyzed the information; it is just that we are not aware of what has actually happened.

When we follow our gut instinct in poker and turn out to be right, it is a great feeling. However, rather than simply congratulate ourselves on our great skill and fine read, it might be more productive to think hard about the situation and try to spot the factors that could have generated our successful hunch. If we can rummage around successfully in the deep pit of our subconscious mind, we might find a useful nugget or two that we can add to our conscious poker arsenal.

Here is an example from an online hand that I played a while back. I have been playing hold'em almost exclusively for a couple of years and feel rather jaded with it. In an attempt to freshen up my play, I have been experimenting with pot-limit Omaha. This is a great game, and I have no idea why it is not more popular. Maybe the thought of having four cards to sort out rather than just two intimidates players (it did me). However, all of the usual poker principles apply, but - obviously - hand values change enormously. Also, drawing hands become much more playable, and are often favorites over strong made hands - a situation that is most unusual in hold'em.

I have forgotten the exact details of the hand that I played, but the basic idea is that I was heads up and in position with a fine drawing hand. I bet the flop, but then when a blank came on the turn, I dogged it and checked. Whether or not I should have bet, I am not sure, but it is irrelevant to the main point of this discussion. There was approximately $200 in the pot when another blank arrived on the river, leaving me with virtually no hand. My opponent thought for a moment, and made a bet that was approximately half the pot.

When this bet plunked down on the screen, I knew - absolutely for sure - that it was a bluff. However, having missed my draw, I had very little hand. I held something like top pair, which in Omaha is perhaps the equivalent of ace high in hold'em. Nevertheless, I called fairly quickly, and was not at all surprised when I took down the pot.

It was a fine result - but I was puzzled. Why was I so sure that this bet was a bluff? I have very little experience in pot-limit Omaha and thought it was unlikely that I had picked up any great clues from the betting sequence. Even if I had, my understanding of the game is so limited that it is hard to believe that I could have fashioned any such clues into a successful read. I checked out my database to see if I had seen my opponent make a similar play in a previous hand, but I had very little data on this person, and nothing to suggest that he would make such a bluff.

I was still thinking about the hand the next day, when suddenly the penny dropped and I understood why I had been so sure that this bet was a bluff. The point is that when you make a bet in an online non-limit game (for example, pot-limit or no-limit), there are generally two ways you can do it. Firstly, you can type the bet size into a box and hit the return key. Secondly, you can use a slider bar to pick out an amount and then click "OK." Since most of online play is conducted purely with a mouse (simply clicking bet, raise, or call), without needing to resort to the keyboard, the "lazy" way is to use the slider bar. However, when using this method, it is hard to make a precise bet unless you are either calling or betting the full pot. If you want to call, you simply click OK, and if you want to bet the pot, you roll the slider over to the extreme right and then click OK.

The interesting situation arises if you want to bet an amount that is more than the minimum but less than the full pot. If you want to make this amount precise (for example, $80 or $100, you have to use the keyboard. If you try to make such a bet by using the slider bar, you will end up betting something like $78.44 or $103.12. It is almost impossible - or at least very difficult - to make a precise bet with the slider bar.

It is easy to analyze my opponent's river bet as having one of the following two meanings:

1. I have a very powerful hand. If I bet the full pot, I know you will fold, so I want to bet an amount that might tempt you to call with a decent hand.

2. I have a busted draw and am bluffing.

If No. 1 were true and my opponent really did have a strong hand, surely he would think fairly hard about the amount that he wanted to bet and would go to the trouble of keying in an exact amount by using the keyboard. In that case, I would expect to see a "clean" bet, such as $90 or $100. However, he had not made such a bet. His river bet had, in fact, been one of those "ragged" amounts - approximately $100, but not exactly. Therefore, he almost certainly had used the slider bar to make the bet - which is just the kind of behavior you would expect from a player who is annoyed at missing his draw and now realizes he must make a desperate stab at the pot. He doesn't bother to make the bet precise because it's only a bluff. That's just what I would have done, and on some deep level I knew it, and it enabled me to successfully pick off the bluff.

So, now I have learned something about no-limit and pot-limit play that I didn't know before. Or, maybe I already knew it - but just didn't know why I knew it. Now I know why I know it - and I can use this information. The next time I have a busted draw, I will bet a precise amount, and when I want to induce a call, I will bet a ragged amount. With a bit of luck, my opponent will blink and come to the same conclusion that I did - but this time he will be wrong.

Byron Jacobs is the author of How Good is Your Limit Hold Em? with Jim Brier, and Beginner's Guide to Limit Hold'em. They are available through bookstores and at www.dandbpoker.com.