Imagine that you are walking in a park. In park, where there are lots of stimuli that you can potentially perceive such as trees, banks, birds, etc. These are environmental stimuli. When you are walking in the park a distinctive leaf captures your attention. Then, you realize that this thing is not a leaf; it is a leaf-shaped bug. Thus, you focus on the bug. The bug becomes the center of your attention. In other words, it becomes the attended stimulus.