Final answer:
The phenomenon by which one fails to notice unexpected objects due to focused attention elsewhere is called inattentional blindness.
Step-by-step explanation:
The phenomenon by which one fails to notice unexpected objects in one's surroundings is known as inattentional blindness. This occurs when a person is so focused on a particular element or task that they overlook other, unexpected stimuli. An example of this is the study by Simons and Chabris (1999), where participants counting basketball passes failed to notice a person in a gorilla costume walking through the scene. Inattentional blindness differs from change blindness, where one fails to notice changes in a visual scene, and visual agnosia, a neurological disorder leading to the inability to recognize visually presented objects.