Final answer:
The Simons and Levin (1998) experiment demonstrated inattentional blindness, showing how individuals may not observe a clear change in their environment when their attention is focused elsewhere, a concept further supported by similar experiments.
Step-by-step explanation:
The experiment conducted by Simons and Levin (1998) illustrated a psychological phenomenon known as inattentional blindness. This occurs when an individual fails to notice a fully visible, but unexpected, object or event because their attention is engaged on another task or aspect of their environment. The subjects in the study were so focused on giving directions to the stranger that when the stranger was briefly obscured and replaced by another person, half of them did not notice the switch.
This concept is similar to the study by Most, Simons, Scholl, and Chabris (2000) where participants did not notice a red cross on a computer screen because they were focusing on black and white objects. Another well-known study by Simons and Chabris (1999) had participants count basketball passes among players, leading to many overlooking a person in a gorilla suit. These studies collectively highlight how our perception is influenced by where we direct our attention, underlining the importance of attention in perception.