A study of 2,000 adults found seeing a loved one get good news, receiving a surprise gift and getting a hug also feature on the list. While others experience the same joy after getting into bed with freshly washed sheets, seeing an old friend and watching a puppy.
But for 46% of people, simply having someone smile at you makes you feel happy, with 65% of adults saying that it improves their mood.
That positive boost lasts for an average of more than 13 minutes, leaving them more likely to be kinder to others (37%), more motivated (19%) or make a bold decision (9%).
Bupa Dental Care commissioned the research as part of National Smile Month, to highlight the benefits the friendly gesture can have. However, an experiment saw just 21% of adults return the friendly gesture from a stranger.
During a two-hour period, actress Zara Naeem smiled at 112 different people as they walked past her – with only 24 replying with the same expression.
Psychologist, Jo Hemmings, said: “When we smile, a number of psychological and physiological changes occur that impact both ourselves and those around us.
“Smiling releases endorphins, dopamine and serotonin – hormones which improve our mood and our sense of well-being – and also reduces cortisol, our stress hormone, making us feel less anxious and more relaxed.
“A genuine and spontaneous smile which reaches our eyes – known as the Duchenne smile – can also lower our blood pressure and boost our immune system, by increasing our production of white blood cells.
“Smiles also have a positive effect on those around us, by reinforcing friendship, kindness and social bonding as well as having a contagious effect, creating positivity in those on the receiving end of a smile.”
The research also found the average adult claims to smile at a stranger five times a week – but 16% admit they rarely or never return the gesture.
Of these, a third blame it on simply being lost in their own thoughts and not paying attention to what is happening around them, while 20% put it down to being in a rush. But 27% avoid smiling at others over fears they will ‘look weird’ and 14% are too embarrassed.
However, when a stranger smiles at them, half of adults feel happy and 32% feel uplifted. Others feel comforted (11%), ‘warm and fuzzy’ (15%) and confident (11%t). Less than one in 10 felt a negative emotion, such as confused (8%) or sceptical (9%).
Despite this, less than half (48%) always return a smile from a stranger, with 34% of those worried the grin was not meant for them. While 32% claim to be so surprised by the gesture that they don’t react quick enough.
But when the smile is not returned, 30% are still pleased they made the effort – as you never know what someone has going on in their life.
Caitlin Miller, head of dental hygiene and therapy at Bupa Dental Care, which is marking its 25th anniversary throughout 2024, added: “The power of a smile is huge – especially when it comes from someone else and is unexpected.
“We’ve all been there, when we’ve missed to smile back at someone, but equally when we’ve caught a smile from a stranger, and it sets us up positively for the day. The impact it can have on you and someone else can’t be underestimated.
“Seeing someone’s pearly whites can give you the boost you might need to get through the day, and the more people love their smile by taking care of the teeth, the more likely they are to share it with others, and everyone can enjoy the benefits it brings.”