Why does Donald Trump shake hands like every time is the first time?

Maybe it's just not fair on Donald 'Tiny Hands' Trump that he's expected as US president to shake hands with other leaders for photo opportunities, because his complex about having little fist-makers means an awkward encounter is inevitable.

To be fair to Trump, the photos of him shaking Justin Trudeau's hand make it look worse than it actually was. Unusually for him, it was a pretty smooth skin-to-skin transaction.

But the Canadian prime minister had already taken ownership of their initial greeting, and deftly neutralised the threat of some handsy chaos by gripping Trump's arm in a kind of alpha male "I'm the biggest ape" move.

Trump has form. When he met the Japanese prime minister Shinzo Abe, he managed to hold on to his hand for around 19 seconds, occasionally patting it to reassure him that it wasn't at all weird, just some really friendly palm-on-palm love between consenting adults.

On other occasions, Trump must show dominance just like he would in his natural habitat. Instead of tossing faeces around, he cranks up the aggressiveness of his handshakes to assert his place in the hierarchy.

Trump patted the hand of his Supreme Court pick Neil Gorsuch to display that he can be friendly if you stay on his good side, but quickly yanked his arm to also demonstrate strength — a primal warning that King Orangutan can and will tear your limbs off if you cross him.

It's the same when Trump clutched Vice President Mike Pence's hand, as if to say: 'Remember who put you here.'

As the dominant male, Trump also knows how to treat women. Just look how tenderly he holds UK Prime Minister Theresa May's hand to send the message: 'I will protect Great Britain, I will protect her, I will beat my chest really hard if I have to, you are precious to me.'

During the Republican primary debates, Trump even allowed his chimp rivals to touch him.

Sometimes, though, he just misreads the social situation.

Maybe Trump should take inspiration from this teacher and develop a different handshake for every world leader.