Ascertainment bias

I really liked learning about ascertainment bias in scientific research. It is when false results are produced because you may be looking too hard for only what you are looking for.

For example, you notice there are so many people in the world who have Birthdays in October. But really, its only because your Birthday is in October, so you are hyper-aware of those birth dates only.

I think that when people give advice they fall under the spell of ascertainment bias too. Maybe a neurologist thinks your problem lies in a pinched nerve, but a dentist insists its an abscess. I have been given some advice lately that I know was only given to me because the speaker has the same issue, and thinks that I do too.

So, if you have experienced something before are you more likely to think the whole world has what you have? or will you be detached and aware enough to admit when something new and mysterious is actually happening, that may lie beyond your scope of familiarity?