Or are you just pleased to see me?

Holding a gun makes you think others are too.

Self-fulfilling prophesies have their uses. Actively imagining a successful outcome, as used by athletes preparing themselves for performance, has obvious applications for moments where self-confidence is crucial. Job interviews, haggling with used car dealers and facing down petulant toddlers all benefit from a mind focused on the desired goal.

They can also work negatively. As the masters of the psych-out know well. 'Are you really going to sprint with your shoelaces like that? Aren't you scared you'll trip?' Planting the image into the opponent's mind, even as an obvious ploy, can be enough to gain an edge. Our perceptions of events and situations are rarely consistent or logical. Which is fine until someone brings firearms into the equation.

"Beliefs, expectations, and emotions can all influence an observer's ability to detect and to categorize objects as guns," reports Notre Dame Uniiversity's Associate Professor of Psychology James Brockmole.

In five experiments, subjects were shown multiple images of people on a computer screen and determined whether the person was holding a gun or a neutral object such as a soda can or cell phone. Subjects did this while holding either a toy gun or a neutral object, such as a foam ball.

The researchers varied the situation in each experiment – such as the having the people in the images sometimes wear ski masks, changing the race of the person in the image or changing the reaction subjects were to have when they perceived the person in the image to hold a gun.

Regardless of the situation the observers found themselves in, the study showed that responding with a gun biased observers to report "gun present" more than did responding with a ball. Thus, by virtue of affording the subject the opportunity to use a gun, he or she was more likely to classify objects in a scene as a gun and, as a result, to engage in threat-induced behavior, such as raising a firearm to shoot.

Scary.