Personal space invasions in the lavatory: Suggestive evidence for arousal. Middlemist, R. D., Knowles, E. S., and Matter, C. F., Journal of Personality and Social Psychology, 1976, 33, 541-546.

Personal space is defined as an area with invisible boundaries surrounding an individual and into which others may not come. People seek comfortable interpersonal distances and will move away when others invade their space. A field experiment was conducted to test the hypothesis that personal space invasions produce arousal as measured by delay of onset and duration of men’s urination. Men using a three-urinal lavatory at a Midwestern university were subjects. According to a previously determined schedule of random assignment a confederate either, stood at the urinal directly adjacent to the subject, stood one urinal away, or was absent from the lavatory. An observer with a periscope was concealed in a toilet stall and recorded measures of urination. He did not see the faces of the subjects. Data were gathered on 60 users of the lavatory, all of whom did not know that they were subjects in an experiment. Delay of onset and persistence of urination were inversely related to closeness of another individual at the urinal. For example, urination delay (measured as the time between when a subject unzipped his fly and when urination began) was 4.8 seconds in the Confederate Absent condition, 6.2 seconds when the confederate was one urinal away, and 8.4 seconds when the confederate was at the adjacent urinal. Results were interpreted as supporting the hypothesis that increased arousal is a result of personal space invasions and this is a probable cause of certain behavioral responses (for example, moving away).