Ever wondered why people close their eyes when they kiss?
According to psychologists, it's so that our brains can properly focus on what's going on.
Researchers from the University of London have suggested that the human brain can't process visual data along with the sensations arriving from our lips.
Polly Dalton and Sandra Murphy, cognitive psychologists at Royal Holloway, University of London, said: "Tactile awareness depends on the level of perceptual load in a concurrent visual task."
So, if you open your eyes and focus on the visual image in front of you while kissing (or doing any other task) it will "reduce awareness of stimuli in other senses".
The study was not focused on kissing specifically, but on broader visual tasks.
Volunteers were asked to perform a letter search task of either low or high difficulty and respond to the presence or absence of a brief vibration delivered simultaneously to either the left or the right hand.
Their sensitivity to the vibrations was reduced when they carried out the more taxing visual search task.
Dr Sandra Murphy said: "It was already known that increasing the demands of a visual task could reduce noticing of visual and auditory stimuli.
"Our research extends this finding to the sense of touch. This is particularly important given the growing use of tactile information in warning systems.
"For example, some cars now provide tactile alerts when they begin drifting across lanes – our research suggests that drivers will be less likely to notice these alerts when engaging in demanding visual tasks such as searching for directions at a busy junction."
The research was published in the Journal of Experimental Psychology: Human Perception and Performance.