Question

Participants are shown a pair of similar pictures separated by a blank interval. the pictures are identical except for a single aspect (e.g., a man is wearing a hat in one scene but not in the other). in these kinds of tasks, participants often find it hard to detect the change. this phenomenon is known as change

Answer 1

This phenomenon is known as change blindness.
change blindness refers to people's tendency to not notice the certain change that happens after they're getting used to a certain visual stimulus
This phenomenon proof that certain amount of attention is needed by a person to notice a change.