This analogy for ADHD is accurate for me:
Brown compared the problem to “erectile dysfunction of the mind”: “If a task you’re trying to do is something that turns you on or that you’re really interested in, you can perform. But if the task you’re trying to do is not something that’s intrinsically interesting, it doesn’t turn you on and you can’t perform. And if you can’t perform in that situation, it doesn’t matter how much you may say to yourself, ‘I need to do this’ or ‘I should make this happen’—it is simply not possible.”
BUT I cannot find many studies that look into this aspect of ADHD or ways that you could reliably measure this in a lab environment.