Final answer:
Inattentional blindness is the term used to describe situations when changes in the environment are not noticed because the person is focused on something else. This phenomenon was demonstrated in a study where participants didn't notice a person dressed in a gorilla costume while counting basketball passes.
Step-by-step explanation:
Inattentional blindness is the term used to describe those situations when changes in the environment are not noticed because the person is actively attending to something else and does not pay attention to other things. This phenomenon was demonstrated in the famous study conducted by Daniel Simons and Christopher Chabris in which participants watching a video of people passing basketballs failed to notice a person dressed in a gorilla costume walking among them. Inattentional blindness is a failure to notice something that is completely visible because of the focus on a specific task or object.