Hi Rodrigo Partida! I’m also interested in exploring the biases in testing so that was definitely a good read for me. I’m bookmarking it for reference.

I recently wrote an article on this (and the guys at UX Collective gave me an opportunity to include it with their publication too). It’s a kind of exploration of what you wrote about membership bias.

I’ve noticed that especially beginners may tend to introduce membership bias. We all tend to pick one of our current hobbies as our first project’s subject, that’s understandable. This makes us feel that we are the insider and may lead to introducing bias. There’s a tendency in this situation to assume that what we know and how we do things is the same as everyone who is interested in the same field. This may lead to missed opportunities and excluding some types of users straight away from our design decisions.

What I proposed is a simple to use approach: reverse any assumption I find in my initial notes. I try to come up with something completely opposite, no matter how outlandish I think it is. Then I validate both and see how the participants (in a survey for example) respond.