Finn was raised and trained for one purpose: to be a trooper in coldblooded service to the apparently fascist First Order. Based on this I'd expect him to have significant anti-social programming. So how is it that as soon as he breaks away he is humorous, likeable, has interpersonal trust (vs organizational trust)? Is there some part of his backstory (maybe in the novel) where he learns to relate in a normal way to other people? Do we know how the First Order training works, maybe it's not so harsh after all?
Update: This is covered in prequel book, Before the Awakening
They do socialize. As a matter of fact, Finn is noted as being unusually isolated among trainee stormtroopers, because reasons (too long to get into and offtopic for this answer)
They had nicknames for themselves
In front of the officers, in front of Captain Phasma especially, they always used their appropriate designations, of course. But in the barracks and in combat, they used the names they’d given one another or the names they’d given themselves.
FN-2199, he was Nines, because he liked the sound of it ....
... and FN-2187 was unusual in not having one:
The stormtrooper fixed FN-2187 with a stare. “No nickname. You’re one of those.”
“One of those what?” FN-2187 asked.
The stormtrooper laughed. He looked to be in his late twenties, perhaps, but there was something hard in his eyes, and the laugh wasn’t amused. “An outsider, cadet. You’re on the outside, and you’ll always be looking in and wondering why you don’t belong.”
They GENERALLY discuss and support group loyalty and group cohesion (it is, however, criticized if it comes at the expense of the mission)
“Yes, sir. While I am entirely in support of unit cohesion, General, a stormtrooper’s loyalty must be higher, as you know. It must be to the First Order, not to one’s comrades.”
They had free time, initially
Free time in which to relax, simply to rest in the barracks or to read First Order–approved literature or watch First Order–approved vids, vanished
At mess, they are typical privates
“I can’t wait to get into combat,” Zeroes said.
They were in the mess hall, all of them rushing to clean their plates. Everything in their day was regimented, an allotted number of minutes for bathing, for dressing, for training, for eating. If you went over on time, someone would come along and take your plate as you were trying to finish. All of them had learned to eat quickly or else go hungry. The result was that if you tried to talk and eat at the same time, you’d end up failing at both. Zeroes’s comment was therefore something of a surprise.
Nines laughed. “You’ve got numian cream all over your chin, Zeroes. Don’t let Captain Phasma see you like that.”
Zeroes wiped at the mess with the back of his hand, then leaned forward over his plate. “It’s coming, you can feel it. No more exercises. An actual deployment.”
FN-2187 looked at him, curious. “You know something we don’t?”
They have a sense of humour. They have a private-rank soldier sense of humour.
“We’re being relieved,” FN-2187 told them. “Captain Phasma wants us to move to a different location.”
“Anything’s got to be better than this,” Nines said.
“You could be a miner here,” FN-2187 said.
“Don’t make me laugh. We’re not supposed to laugh when in uniform, remember?” “I’m not joking.”
It was not covered in the novelization any more than in the film itself, but I think you're reading too much into what makes a First Order stormtrooper.
The purpose of the programming is to instill loyalty to First Order, NOT to make a soldier a lonely psychopath. He still functions in his community (fellow troops), like any normal military.
According to Foster's novelization:
Faces behind helmets stared at one another. With a shock, the trooper who had arrived to render aid to his fallen comrade recognized the one whose life was now bleeding out inside his armor. They had trained together. Shared meals, stories, experiences together. Now they were sharing death together.
Having a sense of humor is pretty much required in the military. Otherwise, you're gonna snap from dealing with all the BS that goes into the non-martial part of being a cog in the machine.
interpersonal trust is far more important to a soldier than to a "normal" person. You trust your fellow person not to steal your food from the company fridge. A stormtrooper trusts his fellow stormtrooper not to blow his head off by accident, when 1000 of them are all firing in the dark punctuated with lens flares.