I am confident that in many countries right now, high government officials are compiling psychological profiles of the President-elect of the most dangerous nation on earth. It will be to their advantage to understand him and how to manipulate him, since he is probably more obviously manipulable than any President in memory.
I've been commenting on his psychology and its disturbance for some time, but I think it can be summed up in terms of two personality traits that we've seen again and again during the campaign, and that mark the man going back to the 1980s, when he was merely the "short-fingered vulgarian" laughing-stock of New York City.
First, he is a textbook case of what DSM calls Narcissistic Personality Disorder. Earlier on, I had described him as a sociopath, but after talking with some clinicians and reading more, it seems to me this is a mistake. Like a sociopath, he is lacking in empathy, but that is true of extreme narcissists too: they are too busy with themselves to notice or care about how others feel. The crucial fact is that sociopaths tend to "fly below the radar," they do not want to attract attention, so that they can proceed with their malign behaviors without detection. Trump always wants to be the center of attention and adulation. Extreme narcissists require adulation because they have no actual confidence in their worth or value: they are entirely dependent on others confirming their grandiose self-image. But the flipside is that when they do not get the external confirmation they seek, they react with irrational rage, that knows very few limits. This is what makes Trump very dangerous: irrational rage on twitter is one thing, irrational rage with U.S. military might at your disposal is another.
Second, Trump has the classic "Mafia mentality" that I've remarked on before, and will be familiar to any New Yorker who has paid attention. In the Mafia mindset, the only question is who is with you and who is against you. Those who are with you, who are loyal and pay respect, benefit from largesse and generosity and protection. Those who are against you, who are disloyal and disrespectful, are to be destroyed, with no constraints on how. Of course, you can't destroy all your enemies all the time, so when necessary you do business with them, until the opportunity presents itself to exact revenge. Because those who are part of the "in group" are beneficiaries of the boss's largesse, they invariably idolize him. Some readers who are old enough will recall the mafia boss John Gotti, who thrived on media attention and showy displays, and who survived numerous prosecutions (it turns out mainly through witness and juror intimidation and bribes), before finally dying in jail. I will never forget in the late 1980s, at the height of Gotti's power, a reporter was interviewing a young Mom with her baby in the stroller in Gotti's Bensonhurst neighborhood in Brooklyn. She was a big fan of Gotti; as she put it, "Thanks to him our neighborhood is safe." Undoubtedly this was true: it would be an imprudent criminal who plied his trade where the consequence for infraction was death and dismemberment. The moral myopia of the in-group permitted the new Mom to ignore the fact that crime and misery elsewhere was due to the same man: what mattered was she and her baby were safe. There is no doubt Trump has the Mafia mentality (if one doubts it, see the choice quote here: "I love to remember my enemies and I love to get my enemies whenever I can, absolutely. ... So many people that were enemies of mine were wiped out, and I do not really care about that." ). Again, this mentality is dangerous in a mobster with guns, but dangerous at a world-historical level with access to U.S. military might.
And like any Mafia don, Trump, of course, prefers family: his "transition team" includes his three adult children and his son-in-law (a fifth of the team, and probably the most important fifth). I suspect one or more of them will end up with positions in his Cabinet or staff.
One reason Trump was so benign and indeed grateful after his meeting with President Obama is because Obama treated him with respect, and they had "great chemistry." Hence Trump's remarkable statement that it was a "great honor" to have met with President Obama. Bear in mind that Trump had repeatedly called Obama the "worst President" ever, denied he was really born in the U.S., and heaped endless abuse on him and his Administration. It all meant nothing, and was neutralized in an instant because Obama, who is clearly lightyears more intelligent than the short-fingered vulgarian, played him perfectly. Rest assured Vladimir Putin understands what happened here. We saw something similar with Trump's praise of Hillary Clinton after she graciously conceded.
Now because Trump is hollow at his core, and because he is an ignorant man who is now wholly out of his depth (I think he is actually a bit frightened right now at being humiliated on an international scale--there is an amusing analysis of Trump's body language here, consistent with this hypothesis), he is probably fluctuating, as narcissists do, to the other extreme of feeling deflated--this probably accounts for his more mellow persona lately. Again, foreign leaders will be watching these patterns, as, no doubt, will those around him, like the VP-elect Mike Pence. While VP Pence will no doubt be discharging a lot of the actual mundane business of governing--which is a very bad thing, of course, but very bad in the way Republicans are always very bad--I am skeptical that Trump is going to effectively defer: he has never done business that way, and I don't think that will change now. On major issues--ones with the potential for generating adulation--the decisions will be taken by Trump in consulation with his consigliere son-in-law, and his children.