I have a few questions about Tactics Trainer -- although it isn't that important. I am just curious.

I see the problems are pulled from actual games. How are the problems' difficulty ratings determined? 

Also - how are points awarded? It seems like if I get it 100% right in the first 3 seconds I get 16 points, regardless of how many moves might be required. Conversely, if I get it wrong in the first 3 seconds then I am discounted 16 points. I assume I am being punished for not thinking about it longer. 

Are harder problems worth more?

Lastly, how come sometimes you play 'til mate and other times you don't? This seems like a difference in style. Are there multiple programmers?

http://www.chess.com/tactics/help.html :)

This is very helpful - thank you! So the points rewarded are based on the average # of correct response times. Ah...

The time allowed would change, but the greatest point value always remained at around 3-5 seconds regardless. So I started to wonder what the relationship was.

Not 3-5 seconds regardless. It is based on the average time. So there are some puzzles with an average solve time in minutes (1+). So those could give a high ragting increase if solved in more time than 3-5 seconds.

For example, one recent one I did had an average time in 1:37 and I did it in 48 seconds, for 90% at +14. Another, average time of 3:09, I completed in 18 seconds for 100%. So it really depends on overall time allowed on how long you have to solve it to get the maximum points for the tactic.

i think if you solve the puzzle, the rating goes down and if you fail, it goes up.

My question on the tactical trainer: When there are multiple solutions or an even better solution, should we post them in a thread such as this? I've only found a few problems like this as I've only done 3 a day for a week or two but there are problems like this. I looked fairly hard but didn't see anything the opponent could do to counter my solutions either.

did you look at the analysis lines under the "view source and analysis" link?  they use some system based on the computer analysis where the point advantage has to be greater than X.  the tactics usually stop when two or more moves are close to the same.  also, you can add comments under the problem. 

What deludes me is how the difficulty rating is determined. Sometimes the solution is as mundane as capturing your opponent's bishop. The only thing I can fathom is sometimes, for example, you'll have a queen and a rook lined up on the h file --- which is the perfect red herring. But it's hard in those first two seconds to weigh material gain over a potential mate. In a real game you have a long term relationship with the location of all your pieces.

in the link eric posted, click on the "glick rating" to see how it works.  so much math i would just say "magic", but the answer is there. 

Basically, tactic puzzles are treated just like a player. They start with some initial rating (may be listed in that link Erik posted) and as players attempt to solve it the tactic rating goes up if it is failed and down if it is passed.

Just like player ratings, the idea is that eventually the tactic will settle in to a stable rating range.

Try not to worry about how much time you have left, just try to solve it. Just like in a real game, you don't necessarily know what is the best move in the situation. Try to find that, and if you can, the continuation, and go with it. Don't get hung up with trying to do it fast.

I must confess, I view tactics trainers as Rocky Balboa views a punching bag.....as a baseball player views batting practice.....as a football player views a tackling dummy.....as the best man at a bachelor party views a blow-up doll.....when its all said and done.....its still only practice.....you can't smell the stench from the armpits of your enemy.....you can't feel them squirm in their seat.....you cant enjoy the anguish of their defeat.....AND YES.....ROWLEY.....IT IS WINTER.....AND I AM BACK ON SITE.....YOUR NIGHTMARE IS BACK!!!!!

Status: Awaiting challenges from infidels.....................

Happy Thanksgiving to you too, studman.