With power centralized more than ever, with complete dominance of Parliament, with absolute control of his party, Stephen Harper is the most powerful prime minister in Canadian history. Or, if you prefer something a little less dramatic, one of the most powerful. I think everyone can agree on that.

But is it good or bad that Stephen Harper is so powerful? About that, we will not agree because our answers are likely to be determined by our ideological and partisan preferences. If you lean Stephen Harper's way, you're likely to cheer. If not, you'll boo. Which makes for a lot of noise but not much light.

So let's ask a different question: Is it good for any leader to be so powerful?

That's a big question. A full answer would have many facets. I'll only mention one. But it's a critical one.

It's the effect power has on a leader's judgment.

Yes, it does have an effect. People sometimes find that surprising. We tend to think that good judgment is an inherent trait, so you either have it or you don't and it's irrelevant whether you happen to have power or not. But much research shows that's not true. The latest is an insightful series of studies.

The first involved a survey of junior to mid-level managers at various organizations. The researchers - psychologists Kelly See, Elizabeth Morrison, Naomi Rothman, and Jack Soll - asked the managers about their authority and their confidence in their judgments. Then they went to co-workers and asked them how good these managers were at listening to the views of others and incorporating what they heard into their decisions.

Of course it's common sense that decision-makers should listen to the advice of others. But should they actually rely on that advice? You might think the answer depends on whether it's good or bad advice. But that's just not true, at least not where there are multiple sources of advice.

"Most of the time, taking advice benefits your accuracy," notes Kelly See, associate professor of organization at New York University. "That's because a lot of times there's some error in your estimate. You may not know what that error is. You may be a little high, you may be a little low." The same is true of other people's judgments, but their errors are likely to be different, so if you pool the judgments the errors will tend to cancel each other out. "When you combine opinions, you usually get a more accurate decision, something that's closer to the truth."

This simple but important phenomenon is why the average guess of 20 people about the number of jelly beans in a jar is likely to be more accurate than any one guess. It's why the average of many polls is likely to be more accurate than any one poll. And it's why prediction markets usually do better at foreseeing outcomes than any one person, no matter how well informed that person is.

But it takes a certain humility to listen to others and seriously take their views into consideration. And power does not promote humility. Quite the opposite.

"We found that the more power the managers had, the more confident they were in their judgment, and the less their co-workers reported that they took advice," See notes.

Was that result a fluke? The researchers devised three more studies, two conducted with volunteers in university labs and a third using a demographically representative sample of Americans on the Internet. The same dynamic emerged in each study: "Power tends to increase people's confidence in their judgment which in turn makes them less willing to incorporate advice."

The researchers also found a modest gender effect in two of the four studies, with women likely to make more accurate judgments because they tended to perceive themselves to be less powerful and so were more willing to take advice. (Feel free to insert a joke about male drivers refusing to stop and ask for directions.)

The bottom line on this research is simple: Power boosts confidence, which reduces the willingness to take advice, which makes decisions worse.

This research is based on relatively modest increases in power but logic suggests great power would have the same effect on a grander scale. So does history. Leaders with the canniness to make themselves dictators have often succumbed to a mad self-regard and the horrible decisions that inevitably follow.

The ancient Greeks understood the danger. They called it hubris. It never made for a happy ending.

The Founding Fathers of the United States understood it, too. The American constitutional system of "checks and balances" was designed to prevent power from concentrating in any one person's hands.

Today, smart corporate and military leaders know the danger as well, and they take steps to protect themselves against it. They disperse decision-making authority. They consult as broadly as possible, with particular effort made to obtain critical and contrary views. And they constantly remind themselves that to err is human and they are human, no matter how many people bow and scrape in their presence.

And Stephen Harper? I must admit the prime minister hasn't invited me over to 24 Sussex to chat about decision-making and organizational theory. I am a distant observer. But I think some facts are clear.

He inherited a government that centralizes authority to a far greater extent than any other in the western world. And he made it more centralized. There is also no evidence - at least not any I am aware of - that the prime minister recognizes the danger confronting him and has taken steps to avoid it. He doesn't disperse authority. Doesn't consult widely and seek out contrary views. Shows not a glimmer of the self-doubt that is the best and final defence against hubris.

Now, you tell me. Should any leader be that powerful?