Which phenomenon describes being unaware of visible stimuli when attention is not focused on them?

The phenomenon of being unaware of visible stimuli when attention is not focused on them is known as inattentional blindness. This concept highlights how our perception is limited by where we direct our attention; when we focus on a specific task or object, we can fail to notice other visual stimuli that are present in our environment.

Inattentional blindness occurs in situations where individuals are concentrating intensely on a particular aspect of their surroundings and may overlook unexpected objects or changes in their field of vision. A classic example of this phenomenon is the famous "invisible gorilla" experiment, where participants focused on passing basketballs often failed to notice a person in a gorilla suit walking through their field of view.

Other options relate to different cognitive phenomena. Inattentional deafness refers specifically to a failure to hear auditory stimuli when attention is focused elsewhere, and change blindness involves not noticing changes in a visual scene, typically due to a disruption like a blink or a cut in a visual display. Distractor stimuli refer more generally to irrelevant information that can divert attention but are not defined by the awareness or lack thereof. Thus, inattentional blindness is precisely the phenomenon that describes the failure to notice visible stimuli when attention is directed elsewhere.