Confirmation bias describes the tendency that we as humans seek out, favor and pay more attention to those information that confirms our pre-made assumptions and beliefs and we selectively ignore information that disconfirms our beliefs.
When people would like something – like an idea or hypothesis – to be true, they tend to believing it to be true. This bias can cause that people will stop gathering further information when the pieces of evidence gathered so far are confirming the pre-made views and hypothesis one would like to be true.
For example, if you believe that a system or solution is usable and will perform well, it is more likely that you will be looking for pieces of evidence that confirm your pre-made hypothesis than to notice pieces of evidence that goes somehow against that belief. Even more this bias often leads to phrase questions – for example in an interview – in a way that is more likely to confirm our own beliefs, so you may get the information you are subconsciously looking for.
So this is a bias that actually you as the researcher/interviewer is likely to experience.
How to minimize the effect:
1) First, accept that you are biased, because we all are, even if that’s a hard truth to admit. Don’t worry, you aren’t alone.
2) As with the effects of demand characteristics especially designers of a product can have a hard time hearing negative feedback about the system they have worked on. So whenever possible it’s a very good idea to have usability tests and the interviews that are connected to them conducted by neutral third parties who are not directly connected to the design or development team.
If this is not possible, it’s important to be aware of the tendency towards conformation bias and always question your perception critically.