Is the belief that a consultant knows more than the team a form of cognitive bias? I've noticed that many people assume that consultants know more than they themselves do and/or more than their team does.  That is, when a team is stuck on a problem, some people believe that a consultant can figure it out even without knowing that consultant. True, more heads might help, but I've also seen teams who believe everything a consultant says, especially at the beginning of the relationship yet scrutinize the people they work with.  Why?

I've read about the halo effect in Wikipedia, which contains the statement, "The halo effect is a type of immediate judgement discrepancy, or cognitive bias, where a person making an initial assessment of another person, place, or thing will assume ambiguous information based upon concrete information."

This would suggest to me that any concrete information can bias someone when filling in the ambiguous information.  However, reading more about the halo effect, it seems mainly focused on how people look.

So my questions are, what goes on in people's minds to create the belief that a consultant knows best when they don't have evidence to believe so?  Is it a bias?  If so, which one?  Or just human behaviour?  Something else?  Does it depend on the situation?
Yes, this could be a cognitive bias. Quite clearly, a consultant is expected to be more knowledgeable about the specific topic they were hired to consult on.


  A consultant (from Latin: consultare "to deliberate") is a
  professional who provides expert advice.


Consultants are supposed to be experts in their field, and as a result they carry some authority. Therefore, authority bias comes to mind:


  Authority bias is the tendency to attribute greater accuracy to the
  opinion of an authority figure (unrelated to its content) and be more
  influenced by that opinion.


The bolded addendum in between parentheses is important. As long as based on the content the consultant brings to the table you respect their opinion, there is no cognitive bias (no irrationality); they are simply doing a good job.

But, not all 'consultants' are experts per se. In software development specifically, I have the impression 'consultancy' has almost become synonymous with 'temporary hire'. Newly grads often get hired straight out of school in consultancy firms. In such cases, there might be a cognitive bias at play, when it is not the contributed content which is evaluated (as you outline in your answer), but merely the title the consultant carries.