Orson lives near train tracks. Trains pass by several times a day sounding their horns. After living there for several years, he often doesn't even notice the sound of the trains passing by. What is this an example of?

Answer: Sensory adaptation

Explanation:

Sensory adaptation is defined as the mechanism in which sensitivity decreases towards any component due to the continuous exposure towards it. This process increases attention towards other element in surroundings by decreasing alertness towards the already exposed stimulus for long time.

According to the question, Orson is impacted with sensory adaptation as he does not become aware by train's sound anymore as he has heard it from many years due to constant exposure. Thus, his senses are adapted to that sound of train and sensitivity is reduced.