Sensory adaptation, also called neural adaptation, is the change in the responsiveness of a sensory system that is confronted with a constant stimulus. This change can be positive or negative, and does not necessarily lead to completely ignoring a stimulus.
One example of sensory adaptation is sustained touching. When you rest your hands on a table or put clothes on your body, at first the touch receptors will recognize that they are being activated and you will feel the sensation of touching an object. However, after sustained exposure, the sensory receptors will no longer activate as strongly and you will no longer be aware that you are touching something.
This follows the model of sensory adaptation presented by Georg Meissner, which is known as "Meissner's corpuscles." Meissner's corpuscles are sensory triggers of physical sensations on the skin, especially areas of the skin that are sensitive to light and touch. These corpuscles rapidly change and adapt when a stimulus is added. Then they quickly decrease activity, and eventually cease to react to the stimulus. When the stimulus is removed, the corpuscles regain their sensitivity. For example, the constant touch of clothes on our skin leads to our sensory adaptation to the sensations of wearing clothing. Notice that when you put an article of clothing on, after a brief period you no longer feel it; however you continue to be able to feel other sensations through it. This is because the additional stimuli are new, and the body has not yet adapted to them.
In contrast, sensitization is an increase in behavioral responses following repeated applications of a particular stimulus. Unlike sensory adaptation, in which a large amount of stimulus is needed to incur any further responsive effects, in sensitization less and less stimulation is required to produce a large response. For example, if an animal hears a loud noise and experiences pain at the same time, it will startle more intensely the next time it hears a loud noise even if there is no pain.
There are many stimuli in life that we experience everyday and gradually ignore or forget, including sounds, images, and smells. Sensory adaptation and sensitization are thought to form an integral component of human learning and personality.