I have worked as a software engineer for a long time, especially in testing and quality assurance activities. I worked in embedded software, or business computing (for banks, airlines and other web companies), with different development lifecycles, from waterfall to Agile. Today, I am still working in the IT testing domain, mainly as coach or trainer.I am a pure scientist engineer. All my studies were about mathematics, physics, and theoretical computer science. So I was very confident in my logical and mathematical skills while testing. And I thought that using a good and logical test plan should make me deliver a quite “bug free” software. But sometimes, I discovered that I could miss very big issues, and I could not understand how this could occur as I trusted the way I tested. So, I started to focus on cognitive science and I began reading some interesting concepts about cognitive biases.A cognitive bias refers to a systematic pattern of deviation from rationality in judgment, whereby inferences about other people and situations may be drawn in an illogical fashion. This illogical behaviour can clearly interfere with our testing ability.If you want to understand that we can easily be affected by a cognitive bias, just think about top-class magicians or the last time you sent back an order to enter a fantastic sweepstakes.But videos are better than words, so please take a look to: