Desireurban has given a good discussion in the first answer, but be careful with it: -- Yes, skimming instead of reading carefully can be non-productive. -- Using credible sources is MORE productive, and using less reliable sources can be LESS productive.
Another nonproductive learning behavior ... one that I worry about a lot ... is slapping the question up on Brainly and waiting for someone to give you the answer, instead of taking some time to think about it.