There's a theory in poker, called the "Honesty Principle". I'll dive further into that in another article, but to summarize it in a sentence, it means that poker players as a whole bluff less than they should.
It's a fact that even the best poker players struggle to keep a perfectly balanced strategy from a theoritical standpoint. There is a growing field of artifical intelligence that's trying to master just that, but for a human it's near impossible to do.
What that means, and more importantly what we can do to improve our game as a result, is that any indivudual player is going to have a betting strategy that is either too value based, or to bluff based. As a result, the majority of players tend to be on the value side of the equation as opposed to the bluff side.
So why? Why is it that as a group, poker players tend to bet different amounts with their strong hands and draws vs their hand that have totally missed the board?
This is where we get into some psychology. Humans are doubtful by nature, and it's hard for us to accept someting before we've actually seen it with our own eyes. Millions of years of evolution have taught us this, and it's built right into our DNA. Suspicion instincively keeps us away from danger, and being gullibe can get you killed (from an evolutionary standpoint - not at the table).
Interestingly, this is the same reason why many players make calls that they shouldn't. There's someting in the back of our mind that makes us want to "know", even if we know the play we're making is likely the incorrect one.
The Honesty Principle At Work
A good way to illustrate how this can come into play at a hand, is to examing a players actions at all stages of the hand. Preflop all the way to the river.
Preflop, most people will not fold AA before the flop (No, I don't want to have the debate about the correct times to fold aces preflop) but with will fold 72o. On the other side of the coin, a player who makes a raise is going to have AA more often than they're going to have 72o. Now, the fact that someone called or raised doesn't mean they specifically have either AA or 72o, but in the event they did, one of these hands is going to be more or less likely.
As we go through every possible hand (I'm not going to list all 1326 of them) we can conclude that people have a preference for playing more profitable hands than less profitable ones. Duh. But what we can learn from this is that this creates a bias that we need to be aware of and apply to later decisions.
After the flop, people will generally continue to apply the same bias. The better your hand, the higher your confidence level in making a bet or raise. A hand like 55 which looked good enough to call a raise preflop starts to look more like 72o on a flop of [Qh][Js][Td] vs four other players. Makes sense, because it's hard to imagine a pair of fives is going to be the best hand in a multiway pot.
This bias will continue through all streets. If you want to see this happen in front of you, watch a few sessions of unedited poker where you can see the hole cards (Live at the Bike or Poker Night in America). You can see a trend among all players, and it's so obvious you probably haven't given it a thought before.
1. Mostly playable hands get to the flop
2. Mostly only hands that improve on the flop will continue to the turn
3. etc, etc...
It's true that some people will do someting different at times, but what we're looking at is the larger pattern. I like to say that an exception does not disqualify the rule, but rather proves that the rule exists in the first place.
Summary
Now, it goes without saying that the analysis to this point is being done in a vaccum and for a large group of players, not indivuduals. Indivuduals do different things at different times. Every situation is only to itself, and when we evaluate a situation at the table it's important we look at it that way. With that said, we also shouldn't ignore the honesty prinicile when making decisions and this is especially important at lower stakes games.
