What's the name and purpose for inclusion of secret elements?

Question

I really don't know how to better enunciate this question. The best way is to go to your profile and see the "hats". This is something StackExchange does at the end of the year. And it's basically some kind of gamification process with no real purpose other than being "festive".

See example below:

However, my question goes around this part of the pattern: what is the purpose of having "secret hats"? It clearly violates rules of UX (specifically Locus of Control) and adds no purpose. Furthermore, it let the user wonder what did she do in order to get that hat. Did she do something good or something wrong? Is this and expression of StackExchange measuring behaviors? And if so, what's the purpose and would this affect users? There's even a leaderboard for this, which suggest this is related to engagement

Independent of StackExchange, what could be a possible use or advantage for this pattern?. There's even a leaderboard for this, but

Also, what's the name of this (anti) pattern? At first I though of Easter Egg, but the concept of Easter Egg goes around DISCOVERING it, not HIDING it. It's hidden, just not completely secret.

Answer 1

I believe there are some explanations for the "hats" (its been around for a few years at least I think) but some are complete mysteries as you mentioned in the question. Generally mysteries create some element of excitement and anticipation, as well as the element of surprise and delight (but only when the basic requirements of user experience are satisfied).

I feel like in terms of gamification principles, it falls more into the 'unlocking' of achievements (without a specific description of the criteria) than anything else. You might even think of them as 'temporary' badges.

There are probably a number of psychological behaviours and mechanisms at work here, but this is probably also a relevant question to ask in meta to understand the intent of this and whether there are similar patterns used outside of the StackExchange network of sites.