False consensus effect
the false consensus effect is a cognitive bias that leads you to assume that other people think the same way that you do. It is natural, and inevitable, and leads to problems in therapy.
It is both good and bad. It is bad when extremists of any sort find confirmation of their own views in the general population. It is good when it allows you to feel more comfortable in a social group.
The self reinforcing effect
The false consensus effect causes you to overestimate the extent to which other people share your own beliefs, values, morals and behaviors. Once you believe this, you stop noticing evidence that doesn't support that, and you tend to reinforce your own view of the world.
You can test this quite easily. Simply ask someone to do something a bit strange, a bit out of the ordinary, something that you might think that would be socially unacceptable or potentially embarrassing. For example, ask your friend if they would dye their hair green. Note whether your friend says yes or no. People who say no, will say that the majority of people would also say no. People who say yes, will tell you that the majority of people would also say yes. They are projecting their own feelings onto the general population. Regardless of what the actual numbers are, people always overestimate in the direction that agrees with how they feel.
False consensus effect and therapy
What does this have to do with therapy? It is important because the way that you deal with your clients reflects your personal beliefs. Your personal beliefs about therapy were determined by how you were trained. How you were trained is determined by the beliefs of the trainer. So once you have these beliefs about how to do therapy, they tend to be reinforced by speaking to other therapist trained in the same therapy. You reinforce them, and they reinforce you.
The problem is that this process prevents you from being open to new ideas, to different modalities, to better ways of doing things. Unless you deliberately set out to challenge yourself, to talk to people from different backgrounds, two experiments with new techniques, you will tend to get stuck in a rut. You will tend to allow your techniques to fossilize, to become more and more embedded in your theory of psychology.
Avoiding the false consensus effect
This is one of the reasons why most therapy associations insist on annual professional development. Going to conferences gives you the opportunity to see a different view of the world. Getting trained in a different modality might well change your perspective on what you are doing, and why you are doing it.
It is something that we all need to be aware of, and something we should all try to avoid.