It's dangerous to know a little about something. It makes us feel more competent than we are.

Remember a time when a friend or relative proceeds to regale us on the proper way to do our own job, despite having no relevant skills or experience. Just the one or two articles they may have read online.

Or the more common experience - perhaps a colleague with the aloofness and confidence of a well-versed expert whose peers wouldn't trust him or her to sharpen a pencil, let alone do the work.

These nefarious clowns are exhibiting a cognitive bias known as the Dunning-Kruger Effect (DKE), or as I like to call it, the Shut Up Dumbass Effect (SUDE - pronounced sud-ee). First described in 1999, Doctors David Dunning and Justin Kruger explained it as "people suffering the most among their peers from ignorance or incompetence, and fail to recognise just how much they suffer from it."

So what they're saying is, people are often unaware of how much they suck at something because they don't know what "good" actually looks like. To be fair, we're all guilty of this.

After a few months of starting Brazilian Jiu-Jitsu, I thought I was pretty talented against other white belts. A tap here, a choke there, I got cocky. Until some higher belts put me in my place and reinforced that ego is the enemy. I was shown what "good" meant.

Again I encountered this as a newly minted Product Manager, where I thought I had a project entirely mapped out and understood, ready to kick ass and take names. Until someone with a decade of experience tore it apart like confetti at a birthday bash. I hadn't done enough user testing, my anticipated metrics made no sense, the experiment timetable clashed with four others currently in play. Basically - I f*cked it all up.

It's vital in our personal development to both recognise when we are falling victim to the Dunning-Kruger Effect, and identifying when others are exhibiting the same behaviour.

For ourselves, when you feel you have all bases covered, ask yourself - if I looked at this with fresh eyes, will I still believe I know everything there is to know? If not, what other angles have you forgotten? If yes, you're still suffering from Shut Up Dumbass Effect, go back a step and ask what different aspects have you forgotten?

When you recognise it in others, you're presented with an opportunity to have an awkward conversation and help them understand the problem. Remember, people think they're good because they don't know what good is. That is the whole premise behind DKE/SUDE. With the right guidance, you can help conquer the mountain together.

Dunning-Kruger Effect goes hand-in-hand with Hanlon's Razor. "Never attribute to malice that which is adequately explained by stupidity". Always believe in the positive intent, and work to better yourself and others.