Perhaps you and your opponent were simply optimizing for different goals ? For example, it's possible that your goal was "defeat the opponent as quickly as possible", whereas his was "defeat the opponent while looking as good as possible (in order to derive maximum enjoyment from the task)" or "defeat the opponent whose challenge level falls within some optimal range, handicapping self if needed (in order to derive maximum enjoyment from the task)" . Your opponent may or may not have been aware of his true goals at the time.
My point is, it's kind of tricky to declare an action "worse than worthless" without having very detailed information about all of the actors involved.
If I am about to go and fence a bout, the color of the shirt that I wear under my jacket is of no concern to me-- but if I had spent significant time before the bout debating over what shirt to wear instead of training, it would become a damaging detail rather than a meaningless one.
Unfortunately, worrying about whether you should worry is also harmful for the same reasons. Luckily, that question should resolve itself more quickly, so it should be a net benefit.
However, in more difficult cases, worrying about whether your should worry is harder to resol...
Despite being at +13, this post has been somewhat controversial, with a positive vote ratio of only 73%-- I'd be interested in hearing what caused some people to downvote it.
My current feeling is that this comment should have been part of the original post-- I thought it was implicit, but evidently this was not the case. Therefore, I'm especially interested in hearing comments from downvoters who downvoted the post for reasons other than the above.
I've had many just such experiences in various sorts of gaming (World of Warcraft, D&D), attempting to teach less-experienced players how to play effectively. (I can elaborate if anyone wants.) I can attest that there's definitely a common attitude of "well, at most this is doing no good, and it's how I like to play".
In fact, one particular aspect of this is that people seem to place value on personalization — doing things their way. The problem is, if there exists some optimally-effective way of doing things, then most deviations are likely to make performance worse (quite often because, as the OP says, the modified/added action consumes resources or otherwise has an opportunity cost).
Here's an example from World of Warcraft:
In group content in WoW (i.e. teaming up with other players to kill big monsters — the high-end, maximally challenging game content), one of the key roles is the damage-dealer, or "DPS" (damage per second). One of the DPS classes is the hunter, a ranged attacker. The hunter's job is to deal as much damage to the enemies as fast as possible.
Like all DPS classes, hunters have a wide variety of damage-dealing abilities, with names like Aimed Shot, Arcane Shot, Serpent Sting, etc. Traditionally, damage-dealing classes use their abilities in complex, shifting sequences, called a "rotation", to maximize DPS. (The reasons for this are beyond the scope of this discussion.)
At one point, I was playing a hunter in high-end raid encounters, and consistently performing very well (doing significantly more damage than anyone else). I would often group with other hunters, who were not performing nearly as well. I often had conversations that went like this:
Other hunter: Hey, how are you doing that much damage?
Me: Oh, I just use Steady Shot over and over. Nothing else.
OH: Haha (they think I am joking)
Me: No, seriously. Look at the damage ...
I wonder what is the equivalent of the Steady Shot in real life that I keep ignoring...
Perhaps "exercise, go out to meet new people, and keep smiling"?
That said, in the more general sense the DPS aggro monkeys were victims of over-fitting
I'm not entirely sure what you mean here. Could you clarify?
Right, sorry, that was kind of a weird metaphor on my part.
Imagine that you're building a classifier (f.ex. a neural network or something) that tells you which houses are "good" and which are "bad". You have a bunch of features that describe each house; among them are longtitude and latitude. You feed some training data to the classifier, hoping that it will draw you some volume in the feature-space. Everything inside the volume is "good", everything outside of it is "bad".
Over-fitting occurs when you don't give the classifier enough training data, and when you punish it too severely for any errors. Thus, it either ends up drawing a really convoluted shape that fits exactly those 5 data points that you gave it; or it ends up ignoring most of the features because they didn't have as much of an impact on the outcome; or both. So, your classifier gets a perfect score on the 10 houses it knows about, and fails miserably at real-world data.
Similarly, these Hunters, and many WoW players in general, have been trained on low-level encounters, where the mobs are weak and the penalty for dying is small. They don't know anything about aggro management, mana conservation, bandaging, etc... All they ever look at is the DPS readout. Thus, when they get to end-game content, they fail miserably.
You can sometimes see the same pattern occur in other situations, too. For example, programmers who are used to working with microcontrollers typically end up writing really terrible host-computer code. Their code is extremely fast and uses very little memory... and is also impossible to modify or maintain. In a microcontroller, using 2x less RAM is the difference between success and failure; on a PC, using 2x less RAM is usually not even noticeable.
e.g. fencing (people are watching you) vs. WoW huntering (no one can see what buttons your are pressing on your keyboard).
You might be right about that, though every WoW move does have a corresponding animation that other people (as well as yourself) can see. I know at least one person who picks their characters based on how awesome they look, but I have no idea whether that is a common pattern or not.
There are things that are worthless-- that provide no value. There are also things that are worse than worthless-- things that provide negative value. I have found that people sometimes confuse the latter for the former, which can carry potentially dire consequences.
One simple example of this is in fencing. I once fenced with an opponent who put a bit of an unnecessary twirl on his blade when recovering from each parry. After our bout, one of the spectators pointed out that there wasn't any point to the twirls and that my opponent would improve by simply not doing them anymore. My opponent claimed that, even if the twirls were unnecessary, at worst they were merely an aesthetic preference that was useless but not actually harmful.
However, the observer explained that any unnecessary movement is harmful in fencing, because it spends time and energy that could be put to better use-- even if that use is just recovering a split second faster! [1]
During our bout, I indeed scored at least one touch because my opponent's twirling recovery was slower than a less flashy standard movement. That touch could well be the difference between victory and defeat; in a real sword fight, it could be the difference between life and death.
This isn't, of course, to say that everything unnecessary is damaging. There are many things that we can simply be indifferent towards. If I am about to go and fence a bout, the color of the shirt that I wear under my jacket is of no concern to me-- but if I had spent significant time before the bout debating over what shirt to wear instead of training, it would become a damaging detail rather than a meaningless one.
In other words, the real damage is dealt when something is not only unnecessary, but consumes resources that could instead be used for productive tasks. We see this relatively easily when it comes to matters of money, but when it comes to wastes of time and effort, many fail to make the inductive leap.
[1] Miyamoto Musashi agrees: