Feynman said "The first principle is that you must not fool yourself and you are the easiest person to fool."
Walter Kauzmann emphasised that people will often believe what they want to believe rather than what the evidence before them suggests they should believe.
Students need to learn skepticism. Furthermore, it needs to be modelled to them by their advisors.
In particular, students should not just believe something because
- their advisor/supervisor believes it or tells them it is true
- it has been published, especially if it is in a luxury journal
- someone famous [or a group of famous people] claims it is true
- it is an exciting idea.
Basic but important questions to ask are:
What is the evidence? How reliable is the evidence?
Is there an alternative explanation, particularly a simpler one?
Maybe I am just becoming a grumpy old man, but I think I do increasingly encounter students and young researchers who lack this basic skill.
I fear that this is because of the seductive power of "sexy" explanations and topics. Furthermore, some of the students mentors and role models don't model or practise skepticism, particularly if their career success and funding [or hope thereof] depends on the exotica favoured by the luxury journals.
Good science is just plain hard work and not as exciting or clear cut as we might wish.