The study isn’t from Oxford. It’s from a team of Chinese scientists (likely in China) who used a large dataset collected in the UK.

The study is published in The Journal of Clinical Endocrinology & Metabolism, which the Oxford Academic collects and reproduces for their academic press.

Is it covert if you know it’s happening and have agreed to it?

It is hard to stay afloat as a comic book store.

It depends on what I’m trying to maximize.

If I just want the happiness spike ASAP, then I would just buy $15 worth of Magic cards, or maybe a booster pack or three, depending on the set.

If I’m trying to maximize my overall happiness over any amount of time, I think spending $15 on something reusable, like a nice pair of socks or a hat would work out for me.

If I want to maximize happiness in general, then spending it on someone else I care about does double duty. It makes someone else happy, and I get happiness from being involved in the process.