my self-reported happiness

I'm not talking about evaluating one's own internal state. I'm talking about outward signs.

I know both high-base and low-base people from, more or less, the same cultural circles. It's not that they would answer the question "How happy are you?" differently -- I don't know, I haven't asked. It's just that the high-base people smile and laugh a lot, are prone to engaging in spontaneous fun, are generally comfortable with life. And the low-base people tend to have a characteristic disapproving expression on their faces (which will actually mold their face by middle age), whine and grumble a lot, and find life generally unpleasant.

Note that here I'm talking about, basically, long-term averages. In the short term high-base people can and will get unhappy and depressed; low-base people can and will get excited and joyful. But both will revert to the mean -- I'm not talking about bipolar people who will oscillate between highs and lows, they are a separate category.