Researchers suspect that the physical warmth of a shower or bath provides people with a substitute for a lack of social warmth, or coldness, in their lives.

In one study, 51 college students were asked to complete surveys about their lifestyle habits and levels of loneliness. Undergrads who felt more socially excluded said they lingered longer in a shower or bath and preferred warmer water temperatures. (There were three questions about bathing habits: How often do you take a bath? What temperature water do you use? How much time do you spend in the bath? All had scale-like answers, plus other questions about lifestyle habits so participants wouldn’t know bathing was the topic of interest to the researchers.)

The effect was sizeable: The degree to which students felt lonely accounted for nearly 25 percent of the variation in their bathing frequency.