Most people kiss with their eyes closed, and it can be offputting to lock lips with someone who has their eyes wide open. A recent study from Royal Holloway, University of London (RHU)  presented a possible scientific explanation for our natural preference for closed-eyed kissing. According to the researchers, focusing on visual stimuli can cause sensory numbness. So, as not to lose out on any of the sensations associated with kissing, certain sacrifices must be made.

For a study now published online in the Journal of Experimental Psychology: Human Perception and Performance, Dr. Sandra Murphy and Dr. Polly Dalton, both from RHU, explored how our brains deal with processing visual and tactile (touch-related) stimuli at the same time. To do this, the researchers had 16 volunteers simultaneously perform a letter search task of either low or high difficulty while they also responded to the presence or absence of a brief vibration delivered to either their right or left hand. Results showed that sensitivity to the vibrations were noticeably reduced when they were asked to carry out more demanding visual tasks.

“It was already known that increasing the demands of a visual task could reduce noticing of visual and auditory stimuli.”  Murphy said in a recent statement. “Our research extends this finding to the sense of touch."

Although the study did not specifically focus on kissing, Dalton told Medical Daily that the ties between her and Murphy’s research and closed-eye kissing behavior do make sense.

“Our research found that engaging in a more demanding visual task reduced people's sensitivity to tactile sensations,” said Dalton. “This does imply that reducing visual demands (for example, by shutting your eyes) can improve tactile awareness, and this could be one of the reasons that people shut their eyes when kissing.” In addition, Dalton explained to The Independent that shutting out visual input leaves the brain with more mental resources to focus on other aspects of the experience at hand.

The same phenomena may explain why we are often oblivious to the sensation of being pickpocketed while we’re focused on complicated visual tasks, such as navigating our way through an unfamiliar city. In addition, the team believe their findings could have real life applications, especially in the design of more effective vehicular warning systems.

“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,” explained Murphy in a statement.

While some people are naturally better than others at multitasking, research has shown that we are all vulnerable to distractions to some degree. According to a 2015 study conducted by researchers from Brown University, subtle and minor distractions may cause more damage than more obvious ones. For example, in the study the team observed how various visual distractions interrupted volunteers from completing the easy task of clicking on a specific icon. Results showed that the volunteers’ actions were more heavily compromised when they were presented with small visual distractions, as opposed to larger more obvious distractions.

Beyond this glimpse into the science behind kissing, the study cements the idea that distractions can seriously take away from our ability to complete the task at hand. So, once again, when engaging in something as serious as driving or walking along a busy road, it’s best to focus all your attention to the task at hand.

Source: Murphy S, Dalton P. Out of Touch? Visual Load Induces Inattentional Numbness. Journal of Experimental Psychology . 2016