Half-Awake: The First Night Effect and the Brain’s Adaptive Response to Unfamiliar Environments

The First Night Effect refers to the phenomenon in which, during the initial night in a new environment, only half of your brain experiences deep sleep. This is believed to be an evolutionary response that helps individuals stay vigilant and alert for potential threats when in unfamiliar surroundings. In addition to causing lighter sleep, the First Night Effect can also lead to more frequent awakenings and decreased overall sleep quality, which may impact cognitive performance and mood the following day.