A polite nod of the head can make a person almost a third more likeable, say scientists.
And the gentle gestures increases their approachability by almost half, a study shows.
The discovery comes three weeks after President Donald Trump successfully mastered the traditional Japanese greeting when he met Emperor Akihito and Empress Michiko.
Eight years earlier his predecessor Barack Obama was jibed at for bowing too deeply.
Now a study published in Perception has shown getting it right improves the likeability of people by about 30 percent and their approachability by 40 percent.
This was compared to figures that shook their heads or stayed motionless and the results were similar for both male and female observers.
The findings shed fresh light on manners and hospitality and could influence the creation of 'avatars' or characters in computer games and even humanoid robots.
The same team previously demonstrated the bowing motion of the computer-generated, three-dimensional characters enhanced their perceived attractiveness.
This time they carried out experiments to rate how simple nodding and head shaking affected perceived impressions of personality.
Short video clips of the figures nodding, shaking their head or staying motionless were shown to 49 men and women aged 18 or over.
The Japanese participants then rated their attractiveness, likeability and approachability on a scale of 0 to 100.
Professor Jun-ichiro Kawahara, of Hokkaido University in Sapporo, said: "Our study also demonstrated nodding primarily increased likeability attributable to personality traits, rather than to physical appearance,"
He said head shaking had no effect on the ratings for likeability and approachability.
In many countries nodding is a communicative signal meaning approval and head shaking denial.
Prof Kawahara said: "The results showed the nodding head motion significantly increased ratings of subjective likability and approachability relative to those of the shaking or control conditions, whereas the shaking motion did not influence the ratings.
"Furthermore it was shown a nodding head motion of the computer-generated models primarily increased likeability attributable to personality traits rather than to physical appearance.
"We concluded head nodding motion is treated as information regarding approach-related motivations and enhances perceived likeability."
Prof Kawahara and co-author Prof Takayuki Osugi, of Yamagata University, said the study is the the first to show merely observing a person's subtle head motions can change initial impressions.
But Prof Kawahara said: "Generalising these results requires a degree of caution because computer-generated female faces were used to manipulate head motions in our experiments.
"Further study involving male figures, real faces and observers from different cultural backgrounds is needed to apply these findings to real-world situations."
Earlier this month President Trump greeted 83 year-old Emperor Akihito and Empress Michiko in Tokyo with a genteel handshake and nod, but no bow.
This avoided the pitfall of President Obama who was criticised by Americans for his deep bow to the monarch in 2009.
After the meeting, Trump shook hands again, and tapped the emperor's arm repeatedly with his left hand. "Thank you for the great meeting", he told Akihito. "I'm sure we will meet again".
Obama also faced criticism from a different quarter - etiquette experts - who noted he combined a bow with an handshake.
This is not done in Japan traditionally, whether meeting the emperor or anyone else.
Trump nodded his head slightly - but did not bend at the waist.
When 6-foot, 2-inch Obama visited the Imperial Palace he made a grand gesture by bowing at the waist to the 5-foot, 5-inch Akihito. Trump is the same height as Obama.