I would like to comment on the paper mentioned above (thanks Coert!). This is interesting, and I find that there’s commonality behind what’s appear as opposites (positive & negative feedback).
Indeed, my first shot was that there is a difference between someone who feels Competent with respect to some learning and someone who doesn’t. I’m using here Competent as in Self-Determination Theory that basically says that intrinsic motivation comes out of promoting Autonomy, Competence and Relatedness (thanks to @Coert for bring it to my radar, BTW).
So, if you’re pointing problems to a beginner, you’re just undermining both their sense of competence and autonomy.
It then seems to me that it all depends on whether someone thinks he’s competent (or autonomous) with respect to some knowledge or skill, or not. So, before feeling competent, you’d need to grow their intrinsic motivation (by praising their hard acquired competence and autonomy), and when they think they’ve come to some kind of expertise, then bringing that kind of positive feedback is just acknowledging the obvious to them and thus not working anymore.
And then for experts (or people who think they are), pointing to problems (gaps between perfection and where they stand) make the unobvious obvious. And if these people are willing to close the gap, then they might want to work on that gap.
I told in the beginning that there was a common principle. Here it is IMHO: it’s about what Gregory Bateson called Information. If you don’t bring information to someone, he won’t act (of course). But if you do, he might react to it.
And what did Bateson called Information? He called Information “a difference that makes a difference”.
So, to someone who thinks he’s a beginner, you point the difference with the beginner: that he’s better than that. To an expert that knows already he’s not a beginner anymore, talking of where he is doesn’t bring information. You’re not stating a difference in his mental model. But if you’re pointing to an unseen difference between his perceived expertise level and some kind of objective/better expertise level, then that is information to him, and he might work on it.
Now the problem is: how can we know where someone think he is on that scale of expertise? Well maybe that Solution Focus scale might come to help here. But then we would need another discussion about how to move up the scale: root cause analyse the gap (no way!) or find times where the gap’s sometimes smaller, and what is done at these times, and do more of it (yes).
Also, furthering the Solution Focus approach to help that expert improve, it might help to ask him about what does he wants more of. Because one can think that although he might be considered an expert when it comes to generalities about some field, he might himself doesn’t agree with that and/or think that inside the field there are some areas where he feels like a beginner.
So in the end, the difference that can make a difference mostly comes out right to someone when the person is giving hints as to where it might be.
Only when someone’s expertise claim to be encompassing might we bring to the table other mental models or situation that the so-called expert might have problems to solve. Indeed, who said one mind has the requisite variety (Wikipedia) to handle two (or more)? No one, for sure as 1 never equaled 1+1.