Comment by bonoboTP

That's definitely insightful. Everyone reaches a level where coasting on smarts is no longer sufficient.

Many reach this realization when starting university, but some can still coast okay in college since the material to learn is well defined and upper bounded. A PhD is not really upper bounded. There's no set out amount of papers to read per week like in a college course. There's no "this won't be part of the exam". Anything is fair game. The returns on being smarter never flatten out, but simply there's no ceiling. You can always do more, read more to keep up with the literature firehose, improve your experiments, your method, etc.

You also need soft skills and a network. You need to keep your finger on the pulse of the community by going to conferences and getting to know people, grabbing coffee or going out to dinner with them. You also need to be slef driven instead of waiting for instructions like it was in college. You need to be just the right amount of skeptical and critical regarding existing methods to be able to come up with new things while being also understood and accepted and seen relevant and exciting by the community.

You also need to manage your time and set your own deadlines and maintain a routine without the external sync given by university lectures and exams. All this basically has no upper limit and even the expectations are vaguely defined. You face rejections maybe for the first time despite having done a thorough work because the reviewers don't see enough novelty or it doesn't slot neatly into what is in fashion at the moment.

My point is that a PhD can push everyone to meet their mental limits. It can be frustrating and it's a notoriously hard period of time for many PhD students. Of course if your only goal is to graduate to get the doctorate, there are possible strategies to "coast", but those who go for the academic path often expect to achieve more than the bare minimum, especially if they managed to coast with good results in college.