You probably think you go about your public business unnoticed.

Maybe you even wear a kind of disguise — baseball cap, sunglasses, wig — to make sure you're as generic and unremarkable as a Sim character.

In your head, of course, you're an urban ninja, making your appointed rounds from coffee shop to comic book emporium to shawarma joint to home again.

But there may be a serious design flaw in your theory. Namely, that everyone can see you.

If you think about it, that should go without saying. You saw the guy in the too-tight Motorhead T-shirt he must have had since he was a kid, walking with coffee that kept spilling over his hand. So why shouldn't he have noticed you in your nobody-will-notice pajama bottoms?

And yet, we insist that we're the ones who do the observing. That psychological phenomenon — the disparity between what we perceive and what we think others perceive — is aptly dubbed the "cloak of invisibility illusion."

(And who said scientists weren't into Dungeons & Dragons?)

Who's watching who?

While a longstanding theory, the theory got seriously tested in 2016, when psychologists at Yale devised an experiment that was appropriately sneaky.

Two participants were asked to have a seat in a waiting room, while researchers ostensibly took their sweet time getting to them.

In reality, the experiment had already begun.

Later, when scientists quizzed each subject on what they could recollect about the other, they offered sharp notes not only on appearance, but mannerisms and behavior.

But while each participant could offer rich details on the other, they were under the impression that they gave away little information about themselves.

"Although people surreptitiously noticed all kinds of details about each other — clothing, personality, mood — we found that people were convinced that the other person wasn't watching them much, if at all," Erica J. Boothby, one of the study authors, wrote in the New York Times.

Man in black jumping through city like a ninja The idea that we can see people but they can't see us makes us ninjas — but only in our own minds. (Photo: Tinxi/Shutterstock)

A case of low-level narcissism

That's not to say you need to warm up the crimping iron before you head out for a supposedly stealth mission to the pizza parlor. In fact, what people note about others doesn't necessarily have to stand out as negative, like say, bad hair or just bad fashion sense.

Another study, a classic from the 1990s, had participants walk into a crowded room with Barry Manilow's face emblazoned on their shirt. Afterward, subjects figured everybody must have noticed the strange fashion decision. But in reality, only half the crowd spotted the "Copacabana" singer's comely mug.

It's not the quirks or missteps or awkward moments that catch the eye. It's really just you. And no matter how hard you try to be circumspect in dress and manner — people are instinctively taking note.

"Whether at a coffee shop, in a waiting room, or riding the bus, people frequently observe the other people around them," the Yale team concluded in the study abstract. "Yet they often fail to realize how much other people engage in the same behavior, and that they, therefore, also are being observed."

Why the disconnect?

You might ascribe it to at least a low-level narcissism that lives in all of us.

"We all have a tendency to egocentrically ascribe our own perspective to others," Boothby explains in the The Times. "That doesn't make us selfish or bad. But it's worth keeping in mind that everyone's attention illuminates the world in a particular way, and what gets spotlighted differs from person to person."

In other words, you might want to leave your invisibility cloak in the closet today, along with the "Ring of Truth," "Gauntlet of Strength +4" and "Boots of Stamina."

And dig out that sweet "Ninja 3: The Domination" T-shirt instead.