Some explain that body language affects qualities like leadership, command, personality etc.:
What is the Buddhist perspective on body language? Does body language affect mental qualities?
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There are many examples in Buddha's life how others were inspired by his appearance. King Bimbisara was tempted to offer him a palace seeing his stature on the first encounter (this was before his enlightenment),
Look at this one, sirs. How handsome, stately, pure! How consummate his demeanor! Mindful, his eyes downcast, looking only a plow-length before him, as one who's not from a lowly lineage: Send the royal messengers at once to see where this monk will go.
"You are young, youthful, in the first stage of youth, endowed with the stature & coloring of a noble-warrior. You would look glorious in the vanguard of an army, arrayed with an elephant squadron. I offer you wealth : enjoy it. I ask your birth : inform me."
Maha Kassapa accepted him as his teacher without hearing a word from him,
On the road between Rajagaha and Nalanda, the Master sat down under a fig tree, waiting for his future disciple. When Kassapa arrived at the spot and saw the radiance of the Buddha's countenance, sensing the enlightenment that shone through it, he thought, "This must be my Master for whose sake I have gone forth!" He approached the Buddha, and paying homage, fell at his feet and exclaimed: "The Exalted One, Lord, is my teacher, and I am his disciple!"
The occasion where Milinda was introduced to Nâgasena in Milinda panha gives some insight on how Buddhist literature sees the influence of body language. Nâgasena was a junior monk, yet Milinda was able to recognize him among others by his demeanor,
And as he looked over the whole of the assembly, in front, and down the centre, and behind, king Milinda detected Nâgasena seated in the middle, and, like a shaggy lion who knows no fear or frenzy, entirely devoid of nervous agitation, and free from shyness and trepidation. And as soon as he saw him, he knew by his mien that that was Nâgasena, and he pointed him out to Devamantiya.
Now, this is a king that gets nervous and frightened by the sight of a monk.
Whereupon the king rejoiced that he had recognised Nâgasena without having had him pointed out to him. But nevertheless, at the sight of him, the king was seized with nervous excitement and trepidation and fear.
This encounter conditions the king's mind, the king has accepted defeat by the very sight of this monk.
'At the sight of Nâgasena, wise and pure, Subdued in all that is the best subjection, Milinda uttered this foreboding word-- "Many the talkers I have visited, Many the conversations I have had, But never yet, till now, to-day, has fear, So strange, so terrible, o'erpowered my heart. Verily now defeat must be my lot, And victory his, so troubled is my mind".