[jurjenh]

The way I've come to see it is "The less you know about a subject, the less you think you don't know."

In other words, you have no solid grasp on the field and so cannot make an effective guess at your ability in the field - so go for middle of the road and that's possibly your best statistical guess...

[jwdunne]

In a way, it's pretty intuitive. Beginners are looking down the rabbit hole and think "well I've got this far so it can't go that much deeper can it"? They've got a CRUD app up and running and doing stuff - I remember I felt pretty invincible at that point.

A prime example from experience: "oh I know development. I use PHP includes all the time".

The biggest humbling exercise I do is to think back 6 months, 1 year and so on. I remember how much I thought I knew and what I produced (some stuff I'm still maintaining too, which is humbling in of itself). Realising how much I've learned between those times and realising I've barely made a dent both shows me how little I know and lights the " I must learn more" fire.

[kafkaesq]

While on the other end of the scale:

"The more you know about the subject, the more you don't know."

Which explains the upper-quintiles topping out at at 70th percentile mean self-rating.