What do you do when it appears that someone has just sort of levelled off in their academic growth? They get the work done, they make progress in their experiments, but their academic development into an independent, critical scientist just isn't taking off?
In those cases, I give feedback whenever the opportunity presents itself, but I try to do it nicely - because I am afraid that I will completely turn them off and/or demotivate them if I'm too harsh. I will point out areas that need improvement - over and over again, but for some reason it's as if they just don't get it. (There are others in the lab that do pick up on these things and I can see that they slowly progress as they become more critical, so it is not something inherent to my overall mentoring, I don't think)
Should I just accept that that's what it is? That some people might just never reach the next level that would qualify them for continuing on in science (mind you, I am by no means of the opinion that that is what everybody should aspire to - we have enough postdocs without the prospect of an academic career-, but as a PI and supervisor it is my job to make sure that come graduation, all PhD students are well equipped to be an independent scientist if they so choose)? Apart from letting them try over and over again (and then showing what holes they missed, which critical steps they omitted, which specifics they just skipped.... over and over again), what can I do? I feel like a broken record, but perhaps I'm playing the wrong song.