British researchers think they may have quantified the precise distance when close becomes too close.
The study, conducted by the University College of London and published today in The Journal of Neuroscience, tested the blinking reflexes of 15 subjects aged 20 to 37, as an electric pulse was applied to a specific nerve in one of their hands.
The closer their hand got to their faces, the bigger the blinking reflex was, and the conclusion was that 20 to 40 centimetres, depending on the person, is the boundary of the personal space bubble.
The University College of London researchers also found, after tallying anxiety surveys filled out by their test subjects, that those with more anxiety traits tended to have the larger personal space boundaries.
University of Victoria professor Richard Gifford has studied personal space extensively and he says a number of other factors play into feelings around what's too close.
"The correct distance varies with person, the other person, the social situation, the culture, what they are talking about, et cetera," he said.
Gifford also says people have a hard time sometimes explaining their personal space needs.
"We learn all these rules as we are growing up, but we couldn't really state the rules, we just learn them as we go along."
CBC News reporter Chris Brown tested out different personal space bubble boundaries in downtown Vancouver Wednesday. Click the link above or the video 'play' icon above to see the results.