endorphin

It's not an endorphin rush, per se, but more of an endorphin creep.

When something is crazy fun to do and gives you that adrenaline boost/endorphin rush/seratonin spike, work can wait...

Living life in a strong, supple body and a trained endorphin reward system makes every single thing more enjoyable.

Nervous voice, endorphin shakes, couldn't even figure out which bit of paper was the registration at first.

Also, in my experience, The endorphin high seems to last longer than a high intensity workout.

Small shocks could be mildly pleasurable due to the endorphin response, similar to the mechanism that makes spicy food pleasurable.

It eschews the idea of endorphin-releasing actions with the sole purpose but draining cognitive reservoirs.

Motivation starts rearing its head strongly when body picks up on the endorphin high.

You get the added benefit of endorphin-fueled contemplation of the project you're working on.

Your specific point -- that endorphin hit you get is a social reinforcement for a positive contribution to the community of Hacker News.

You need to be exercising every day to get all that endorphin goodness and plus, you meet a lot of fun people at crossfit.

They do it because it gives them little endorphin pops to think about how upset their victim must be and because it's very low risk.

I'm more productive during my "silent endorphin" rushes than any other time of day.

“We think that’s what they exist for, to trigger endorphin responses as a consequence of grooming,” Dunbar said.

I stopped at "...little is known about the social effects of pain." A long time ago I was reading Marine Corps training manuals at USC's Doheny Library (a friend was doing an endorphin study and the Marine's apparently had some some interesting work there) and I can tell you that they not only knew about the social effects of pain, they employed those effects in a variety of training exercises.