Monday, 25 November 2019

Christmas tree decorations and happiness

The New Zealand Herald reported yesterday:
A psychologist says Christmas decorations bring a sense of nostalgia for happier times and, as such, do make people happier.
"In a world full of stress and anxiety people like to associate with things that make them happy and Christmas decorations evoke those strong feelings of the childhood," psychologist Steve McKeown told Unilad.
According to McKeown, those decorations work as visual cues and a pathway back to those feelings of excitement of childhood...
A study published in the Journal of Environmental Psychology also showed that there is a correlation between decorating your home for Christmas and seeming friendlier and more social to neighbours.
The key word in that last sentence is correlation. Just because you can tell a cool story that seems to explain some observed relationship between two variables, it doesn't make that relationship causal. In this case, just because people who put up Christmas decorations are happier, it doesn't mean that decorating causes people to be happier (regardless of nostalgia or whatever).

Perhaps happier people are more likely to decorate (reverse causation). Perhaps people who are less stressed at work and have a better work-life balance are both happier, and more likely to find the time to decorate for Christmas (a third variable, work-life balance causes both happiness and decorating). Or perhaps, the observed correlation is just spurious (like the excellent selection at Tyler Vigen's site, Spurious Correlations).

As an aside, I can't find the Journal of Environmental Psychology article that McKeown refers to, unless it is this one from 1989 (gated), which doesn't mention happiness at all! All in all, this story is a bit of a fail, and as always, it pays to take these claims of causal relationships with more than a pinch of salt.

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