Many people have the habit of leaving a glass of water by the bed before sleeping, although they often discover it remains untouched and must replace it the following night. Although at first glance the behaviour might seem wasteful, psychology experts argue that it responds to a deeper emotional need than simply being thirsty during the night.
Experts explain that the brain seeks to reduce uncertainty even while resting. Knowing that certain resources are available, even though they will probably never be used, generates a sense of calm that favours sleep. In this sense, the glass of water serves a symbolic function: rather than satisfying a physical need, it represents the certainty that if something happens during the night, a solution is already prepared.
This phenomenon is related to what is called the "illusion of control", a concept studied by psychologist Ellen Langer in a paper published in 1975 in the Journal of Personality and Social Psychology. Langer's research showed that people tend to feel safer when they perceive that they have some degree of influence over a situation, even when their actions do not actually change the outcome.
Psychologists refer to these behaviours as "safety behaviours": small actions that people perform to feel prepared in the face of possible difficulty. The glass of water functions as a signal to the brain that a future need has already been considered. In this way, many apparently insignificant nighttime habits serve important emotional functions in the search for anticipation and security.