Interviewers tend to have one of two different mentalities...
Some are trying to see you fail. They're looking for a reason to say "no". They tend to not be of any help on a problem, will often try to find ways to trick you. They also tend to have an ego problem -- you need to prove to them that you're worthy of joining the team.
The other class of interviewers are those that want you to succeed. They will answer questions, and help clarify things. Even if you are unqualified for the role, and they know it, they still want to help you along so they can see your best work. People that shut down when they get nervous tend to open up to these interviewers. They also tend to be the people that are more pleasant to work with.
Some are trying to see you fail. They're looking for a reason to say "no". They tend to not be of any help on a problem, will often try to find ways to trick you. They also tend to have an ego problem -- you need to prove to them that you're worthy of joining the team.
The other class of interviewers are those that want you to succeed. They will answer questions, and help clarify things. Even if you are unqualified for the role, and they know it, they still want to help you along so they can see your best work. People that shut down when they get nervous tend to open up to these interviewers. They also tend to be the people that are more pleasant to work with.