Observations or stalking? Which one is it Ted? I have a friend who enjoys having his morning coffee, and we think, afternoon coffee, and evening coffee while watching the locals pass him by. Let's just say we think he has "an office" at every local Starbucks. He's always checks in on Facebook and tags it as "observations." We think Ted, I changed the name to protect the semi-innocent, we think he majored in observations in college for he does it so well. But here's a little bit of scientific advice, Ted. New research from the United Kingdom states that the perfect amount of time to stare at someone is about 3.3 seconds. If Ted will stare longer than that or even pull away his gaze sooner, it'll be creepy to the other patrons.
Visitors to the London Science Museum judged whether videos of an actor looking at them for different amounts of time felt too long or too short with respect to what they deemed to be comfortable. Behavioural and physiological measures were combined with basic demographics and personality questionnaires to determine whether trait characteristics influenced gazing behaviour. – royalsocietypublishing.org
How long do you think you should glare at someone? How long would you like someone looking your way? I think for me it all depends on the eyes, the facial expressions and the other body language.
In this study, we provide the very first large-scale quantification of preferred direct gaze duration and relate this measure to eye tracking, physiological, demographic and personality indices. We find that, on average, participants have a PGD of 3.3 s, consistent with earlier reports obtained in dyadic interactions, i.e. 2.95  and 4.66 s . We also find that changes in pupil size are indicative of a participant's experience of preferred duration of eye contact. Pupil dilation increased at a faster rate in participants who preferred longer periods of direct gaze. – royalsocietypublishing.org
I am not sure if I look at someone so intently that I would notice their pupil dilation and I know I don't notice my own dilation. I'm more apt to notice if my face becomes flush as I blush or the feeling of my skin crawling. If I have to notice dilation, there goes any game I would hope to have.
But say you really like what you see, and you want to keep subtly staring without getting slapped.
In that case, position yourself diagonally from the recipient of your stares, says body language expert Marc Salem, the author of The Six Keys to Unlock and Empower Your Mind. People interpret side glances as less invasive than straight-on stares, he says.
And when you’re talking to someone, keep your eyes on the bridge of their nose, says Salem. This will seem less intrusive than if you were to stare right into their eyes. – menshealth.com
So I do not know if any of this helped or not. As well, this study was done in London where the British may have different upbringing around staring, manners, and politeness than other parts of Europe, the World. Would these results be different if the study was done in your country?