A clock that once seemed loud fades into the background after an hour. Habituation is the decrease in response to a repeated, harmless stimulus. It is one of the simplest forms of learning.

Habituation allows organisms to ignore predictable, non-informative events and conserve attention for novelty or change. It is stimulus-specific; a slight alteration can restore the response (dishabituation). Infants show habituation to repeated visual patterns, providing a window into early perception and memory. In adults, habituation appears in sensory adaptation, reduced startle, and the fading of emotional reactions to familiar stressors.

Researchers use habituation paradigms to study attention, learning, and certain clinical conditions. Failure to habituate can leave a person overwhelmed by ordinary stimulation. The process demonstrates that even at the most basic level, the nervous system filters experience according to relevance.

What we cease to notice frees capacity for what still matters.