Because “common sense” isn’t always accurate and can vary wildly like between cultures. One example is the idea that same-sex parents (especially two men) would “obviously” be worse parents than a man and a woman. Where I grew up, this would be common sense, but where I live now, you’d get ridiculed for expressing that idea. The literature generally finds that same-sex couples’ children tend to have better outcomes, due to fewer “happy accidents” for them and the general need to have a higher income to get approval for adoption or to support a surrogacy.

Studies also help you identify what factors can make a statement more or less accurate. For example, with this study, it would be interesting to see how the diets compare between Slovenia and wealthier western countries. I’d imagine students with higher proportions of hyper-processed food in their diets would see less of a decrease in weight.

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