I was at the DMV the other day and I had to walk in front of like 100 people to take care of my car registration. I had a stain on my shorts—a McRib stain to be exact. I felt like everyone in the whole place noticed it. I'm sure you all have had similar experiences, albeit without the McRib. But, I was probably, really, really wrong, according to research on the "spotlight effect."
The "spotlight effect" refers to the tendency to think that more people notice something about you than they do. Dozens of studies in social psychology have supported this phenomenon. In one test, some students wore bright yellow Barry Manilow t-shirts to a large introductory to psychology class. They then had them estimate how many people in the class they thought had noticed. They greatly overestimated.
So what explains the "spotlight effect?" Basically, it is the result of egocentrism. We all are the center of our own universes. This is not to say we are arrogant, or value ourselves more than others, but rather, that our entire existence is from our own experiences and perspective. And we use those experiences to evaluate the world around us, including other people. But other people not only lack the knowledge of, for instance, the stain that you have, but they are the center of their own universes too, and in turn, are focused on other things!
Naive realism and the bias blind spot also contribute to this. For instance, people typically do not perceive themselves as biased.They tend to assume that what they are focusing on is accurate and objective. In turn, they believe that most other people should notice what they are focusing on; it is (in the mind of the person) objective and accurate, after all!
Combined, this creates a situation where people are (1) using their own experiences and cognitions about themselves to evaluate other people's thoughts and behaviors, and (2) overestimating the extent to which their perceptions are shared by others and are accurate.
The result is that people think more people notice stains on shirts, and the like, than actually do.