Stephen Harper has done everything from playing the piano in public to tweeting a prime minister's day to soften his austere persona. Then came the meeting earlier this month with Darcie Clark, whose former husband killed their three children.

Afterward, talking with reporters, Mr. Harper at first found it difficult to speak.

"Once you become a parent, you see the world through a different lens," he explained, his voice growing increasingly unsteady. "Given the love we all have for our children, one cannot begin to imagine the pain and suffering that this kind of event brings about."

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The moment passed, and the Prime Minister went on to promote new Conservative legislation that would make it more difficult for those found not guilty of crimes through mental illness to be released.

One of the least-understood qualities of this complex politician is the shield he uses to protect himself from the public, a defence that so rarely slips.

"A lot of his persona has been misinterpreted, because he is an introvert by nature," offers John Weissenberger, a long-time friend of the Prime Minister.

"Someone who is by nature a reserved person is often seen as cold and unfeeling," he explained in an interview. "But there are glimpses. When you see him meeting with families who have suffered personal loss … he shows that he can be deeply moved by things."

Aaron Pincus is a psychologist at Pennsylvania State University who has, among other things, examined introversion.

"Being an introvert doesn't mean that you lack some skill that you should have," he said in an interview. "I don't see introversion as the same as being shy or socially anxious." Instead, it marks "a preference for a certain interpersonal distance," he said. Introverts gain strength from having time to themselves, while an extrovert draws energy from being with others.

Yet from an introvert's contemplation can emerge powerful convictions. Stephen Harper came of age during the era of Reagan and Thatcher, in the last decade of the Cold War, and drew from those experiences permanent lessons.

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One of the reasons he ran for public office, Mr. Harper said at the press conference, was that he believed "profoundly" that the criminal justice system had "become unbalanced in a way that was really inexcusable."

Mr. Harper also believes, said Mr. Weissenberger, that Canadians had lost touch with their past, especially their military past; that foreign policy was, as Mr. Harper puts it, too willing to "go along to get along;" that the federal government had become too intrusive in the affairs of the provinces and the lives of the people.

However you may regard these convictions, you cannot question the depth of them. "He wouldn't be in politics if it weren't for his philosophical beliefs," Mr. Weissenberger said.

Prof. Pincus acknowledges that introverts can have a harder time getting ahead. "People prefer interacting with extroverts more than introverts," he said.

"Extroverts, controlling for everything else, do better on job interviews or admissions interviews or getting-elected interviews."

But if an introvert can make it into public office, he or she can bring qualities that extroverts lack.

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"Introverts are more likely to be able to make the tough decision because they don't need everybody to be their friend," he explained.

And because the public can sense how difficult it is for an introvert to run for office, they may trust his or her judgment more than an extrovert, whom voters may suspect is just in it for the applause.

That doesn't mean that Stephen Harper's vision for the country is the right vision. But it does help explain how a man whose smile is demonstrably forced, who would rather be filmed working alone in his office than working a crowd, whose defences crack only when confronted with the raw grief of a mother whose children have been taken from her, can win three consecutive elections.