Habituation

Habituation is a decrease in response to a stimulus after repeated presentations. It is considered to be one of the simplest and most common forms of learning. Habituation allows people to tune out non-essential stimuli and focus on the things that really demand attention. If the habituation stimulus is not presented for a long enough period before a sudden reintroduction, the response will once again reappear at maximum strength.  This is something that happens regularly in your everyday life and it often goes unrecognized.