When Dumbledore made eye contact with Harry Potter to see how he felt about Hogwarts, like he did all new students, to find if there was some concern, he was not expecting his attempt to terribly backfire.
Harry Potter has always heard voices.
Ever since he could remember, he could hear the voices of people, even when their mouth wasn't open.
The voice got louder every time he made eye contact.
By age six, he understood what they were. They were other people's thoughts and emotions, and he's been able to read thoughts and see memories, and if only to stop the Dursleys, he began practicing his ability to know when they were near their tipping point to top doing whatever it was he was doing.
By age ten, he knew he was a wizard, plucked it right from Mrs Figg's and Aunt Petunia's memories, and took it upon himself to know what kind of magic it was he was doing.
Then his Hogwarts letter showed up and the voices of his relatives had never gotten louder, the worst part was that they were filled with profanity he was sure wasn't appropriate for his age range.
Then, when he was nearing his breaking point from Uncle Vernon's personal rants, he just willed it to shut up for five minutes. It did. Curious, he began willing Aunt Petunia to let him peek at the letter, slowly since he was so unused to it, and if she "accidentally" dropped the letter by the cupboard, it was no one's business but hers. The freak might as well know what he was.
When it worked, Harry began willing them to let him go to Diagon Alley (once again taken from Aunt Petunia's memories) after he answered by willing a pigeon to take it for him, owls avoided Privet Drive like the plague after all.
Turns out, slightly intelligent animals have thoughts he can understand too. Which was awesome.
He avoided eye contact and tried to ignore the voices of the two people in his compartment, he knew they meant well and all, but hearing their gushing thoughts after finding out his name and how it was an unreal coincidence, he felt bad willing the thoughts and decisions of not-pricks his age who hadn't done anything wrong.
He did will the blond git's mind to believe that there was a man in a bathrobe holding guns outside trying to intimidate him so he left.
And then it was time for the sorting feast, and when he accidentally made eye contact with the headmaster, his head was filled random fragmented thoughts and sudden memories.
When he managed to pull himself from that pool of memories of the headmaster's childhood and romantic life, he firmly stopped looking at people, trying to avoid his flushing from getting worse after seeing things an eleven year old shouldn't be seeing.
Then the same thing happened with the sorting hat, at least this one didn't have romance, but it did end up with him reading a *hat's* experiences, which were apparently not much, but he learnt some juicy gossip from the minds the hat had read in his first twelve years of creation, as well as the secrets the founders only shared with the hat.
The hat screamed and flung itself from him while yelling Gryffindor.
At least he knew the house he wanted?