After seeing 27 comments on FSP's post, I've added a bit and brought the post to the top - as I commented and posted a link here.
Again, over at FemaleScienceProfessor, there is an interesting post regarding confidence. Or lack of.
I know a person, exactly as FSP mentions, who has a "colossal lack of confidence". I put it in brackets, as I am not sure whether it is or not (and I don't know the person very well - I have observed her a few times, which led me to the conclusion). I think the person does not know how to take criticism, or understand that there are alternative ways of doing things.
Everything has to be done her way, in her time. Obviously that is not the way things work in a lab where you have other people working beside you.
Anyway, going back to the original topic of confidence. The question asked was:
Can a lifetime of lack of confidence be overcome during graduate school?
Personally, I think it is hard to overcome that during graduate school. Why? Because you are still considered a trainee by all accounts - and that includes taxation in this country. Being in graduate school is only slightly different from being an undergraduate. There are a lot of things you can get away with, which (in my view) you shouldn't or couldn't when you are properly working. Having said that, being a postdoc isn't much different sometimes. You just pay tax.
Anyway, let me change tack here and talk about a practial solution to change.
FSP mentions about coping mechanisms. One very good coping mechanism is disengaging your self-worth from your job. If you consciously think that criticisms to your work, has nothing to do with you as a person, it makes life a hell of a lot easier. This disengagement is crucial if you want to make working life easier for yourself. And for me, it is something that has come along with time.
Another thing, which goes hand in hand with the above point, is to understand that these are other people you are dealing with. They have their own agenda. They are different to you. This is something that is hard to really grasp, and really appreciate, when you are in your early-20's. Hell, it was, for me.
So the next time a postdoc is criticising your experimental procedure, you can think that it's all your fault, or:
(1) the postdoc just doesn't like you because of the way you dress, or
(2) the other half of the said postdoc is cheating on him/her and he/she just found out, or
(3) the postdoc just had his paper rejected, or
(4) the postdoc just lost a fellowship he was writing due to a computer fault, or
(5) the postdoc couldn't sleep last night because his next door neighbour was playing music too loud.
i.e., it is absolutely, not about YOU.
As FSP mentions, there may not be much that an advisor (or even a friendly postdoc, i.e. someone senior but helpful) can do. It sounds cruel to say, but sometimes such people with extreme lack of confidence can be thought of as being overly concerned with themselves. They are too self-conscious. They cannot, and sometimes do not, see themselves as being part of a society - it is just them, against others. And they often see the others as enemies.
In a way, they are consumed with themselves, which you can call a type of narcissistic trait without the ego or self-love. A negative narcissist (I'm sure there's a psychological term for it, but hell if I know).
The problem here is that such people do not listen to advice easily, because advice given to them is an "external" input. Something inside has to trigger a reaction - they have to have an inner reason to want to make life easier for themselves.
I've noticed that the comments for the post over at FPS is full of people suggesting counseling - which I think is the best way to go. I think the student in question will respond well to counseling, which is basically talking and analyzing about yourself to someone without their own agenda (but to help you).
But the point is, all of them wanted to do something about it. And the key is, the want to change must come from the student him/herself. FSP can help by letting the student know that his/her attitude/personality will not be helpful in his/her scientific career. She can help by suggesting counseling. But whether the student listens to her or not, is up to the student.
And that is where FSP, or any other person's influence stops.
What else?
The quickest way to change a person is to have something catastrophic happen to them - to shock their way out. Something that makes them evaluate their ways, their habits, their life to an extent. The person will not change overnight, but hat something will make them recognize the "problem".
Which is stupid, because a catastrophic occurance cannot be planned, and the person cannot know when, where, what or if it will happen. And it will be painful to them, because...well, it is catastrophic.
Otherwise, only time and change of circumstance (such as graduation) will help.