When it comes to promises of good behaviour, Parliament is the hill where hope for change goes to die.

Every prime minister - including Stephen Harper - has repeatedly pledged to show more respect for decorum and party differences, only to watch the centre aisle collapse into an echo chamber of cheap shots and yelps of unparliamentary language.

Behaving badly, you see, is an occupational hazard for MPs that's hard-wired into the system.

Take one room and mix together more than 300 people who campaigned against the other side, with the clock ticking down to the next survive-or-die showdown, and any sunny-side-up disposition gets scrambled in a hurry.

But maybe - and I don't want to sound too Pollyanna about this - but maybe the notion of co-operation over confrontation will linger longer than usual in the 42nd Parliament.

The new Speaker is mild-mannered with a low tolerance for partisan nonsense and should referee fairly.

The acting Conservative Leader, Rona Ambrose, has lowered her sharp partisan elbows and is arming for battle over the economy instead of petty policy differences.

Even NDP leader Tom Mulcair, who feigned forgetfulness Thursday by insisting his party never heckles, will find it difficult to excel in articulate anger without major scandals like the Senate to arm his evisceration of the government.

And if there's going to be a return to the viperous antagonism which so completely dominated the parliamentary landscape last spring, it's difficult to see it resurrected by Justin Trudeau.

The new prime minister didn't rise to the bait when Conservative and NDP war rooms carpet-bombed him with smears and jeers for almost every one of the 75 days of the campaign. A few uncomfortable questions in the Commons will be unlikely to wipe away his happy-face demeanour.

Of course, even the most docile mice can be conditioned to become rats when sufficiently provoked, so it's with time-tested trepidation we await the transformation of fresh-faced rookies into rabid partisans.

But yesterday's MP mingle in the middle of the Commons was the most cordial return to Parliament I've ever seen. Backslapping, handshaking , hugging and selfies erupted on all sides with no signs of party divisions.

It may just be a blip. But, because it's 2015, maybe that's what real change looks like.

And that's the Last Word…