There are two (2) types of gamblers: first is the one who chases for profits; the other is the one who finds it purely for entertainment.
Actually there are more type than that.
Some gamble due to curiousness, other for social benefits and more.~
I don't know, can't all that be labelled as entertainment? I mean, I agree with qwertyup23, your goal can be either getting money, or getting entertainment from gambling. With this simple classification we can easily separate what's wrong from what's right.
When you started spinning slots with entertainment purposes in mind, but in the process of the game, after losing $20 you suddenly want to win it back, you should know you are stepping on the wrong road.
Curiosity is neither of those though, so I think it is definitely more, but well does it matter? I think not as long as we are able to control ourselves and not get lost in the process of engaging in gambling. The type is actually used to treat kinds of gambling addiction. Something to do with the root cause so it is quite important for the medical practitioner to know this type of gambler.
But, well it is always better to simplify stuff to identify the right path and the wrong path. And in your given case, I greatly agree that when that thing that you stated happen, (a player starting to chase his losses) the player is indeed going to the wrong path and is very concerning because it might make that person's life miserable if he failed to notice it and stop chasing loses.