There has always been a view that performing the haka has given the All Blacks an unfair advantage. The Brits, in particular, have issues with it, saying it provides the All Blacks with an exclusive opportunity to intimidate.
But there is evidence emerging that the haka is more of an emotional hindrance to the All Blacks than an effective means of intimidation. It might be that the haka does a better job of unsettling the All Blacks than the opposition and it hasn't gone unnoticed by the All Blacks coaches.
"We're poor starters," coach Steve Hansen said before last week's test against England. "We haven't quite got it right so maybe we are over-aroused or under-aroused."
Read more: All Blacks off balance by the haka
Having such intense emotion in the minute before the game kicks off might be the reason the All Blacks don't have a track record of starting games well.
In the 31 tests played under head coach Steve Hansen, the All Blacks have conceded the first points in 17. In seven of those, they conceded the first points within five minutes and in another seven, conceded within the first 10 minutes.
In four of their last six tests, they have conceded the opening score and each time it has come within the first five minutes.
As theatre, the haka is unrivalled. It remains a critical mechanism by which the All Blacks can express their identity and acknowledge their history. It's hugely important to the players and All Black brand.
It is going to be done. No one thinks otherwise. But considered purely from a sports science perspective, it's questionable whether it makes sense.
Preparation is everything to the All Blacks. They train, plan, talk, train some more, plan some more, talk some more and, after six days of that, are finally ready to play a test.
And then having spent so long getting into the right mental state, the last thing they do before kickoff is, en masse, heighten their arousal levels. This, so the theory goes, is where their advantage lies. They are given free reign to get 'psyched up'.
But heightened arousal doesn't mean optimum arousal. After they fell apart at the 2007 World Cup, the All Blacks devoted themselves to studying the brain and understanding how it works. Mental skills coach Gilbert Enoka wanted to form a total picture of what happens to players when they perceive they are under pressure.
He told NZ Rugby World: "The brain essentially has three parts: instinct, thinking and emotion. Invariably under pressure, it is the thinking that shuts down and that means you are relying on emotion and instinct and can no longer pick up the cues and information to make good decisions.
"We spoke a lot about connecting, about staying connected. That was important because, if you become disconnected, then you can focus on outcome and not task and the ability to make good decisions is compromised."
The All Blacks talk of red heads and blue heads, with the former being an undesirable state - not focused on task, stressed, panicked and ineffective.
Blue heads are aroused but focused - stimulated but not over stimulated. It's what is meant by 'being in the zone'.
The haka may create red heads. It might be that players, maybe not all of them, take some time to come back to being blue heads after the haka. There may also be some truth that the haka has the secondary effect of helping some opponents get their blue heads. Over the years, various teams have tried different ploys when facing the haka.
Some have backfired - Tony Underwood winking at Jonah Lomu in the 1995 World Cup semifinals and Australia steadfastly ignoring it in Wellington a year later. But France in 2007 and 2011 seemed to take all the energy from the haka and use it to their advantage.
"At the end of the day," former England lock Nigel Redman told the Daily Telegraph, "the haka is about a guy who has been betrayed by his villagers. He has been a bit of a tyrant and he hides himself away in a hole. When you translate it into English, it's hardly inspirational, is it?
"If you're into rhythm, beat, that sort of thing, you can get a lot out of the haka yourself. I used to pick the person who I thought did it the best, stand opposite him and tap my thighs to the rhythm of the beat. You have to watch it, accept it and then use the energy to your advantage."
Opposition responses to unsettle the All Blacks
Ireland captain Willie Anderson decided he wanted to turn the table psychologically on the All Blacks by being proactive as opposed to reactive in the way they faced the haka. Anderson famously asked his team to link arms and advance towards New Zealand as they performed. It was dramatic theatre and, arguably, Ireland benefitted from their strategy. They lost the game - but everyone lost to the All Blacks in 1989 - yet played well for 60 minutes. They surprised the All Blacks with the intensity of their performance and New Zealand eased into relative comfort only in the last 20 minutes.
"I spoke to Buck Shelford after the game," Anderson told the Herald on Sunday in 2005. "His view was that they threw the gauntlet down and we picked it up. I have nothing but respect for the haka and it's a major rugby tradition. I don't think anyone would want to see it lost from the game."
NZ 43 Australia 6
On a dreadful winter's day in Wellington, the All Blacks lined up to do the haka and, down the far end, the Wallabies blissfully ignored them, preferring instead to carry out some warm-up drills. So the All Blacks carried on, finished up and then went on to give one of the greatest performances in rugby history when they made only five unforced errors in the most atrocious conditions. The Wallabies were awful for 80 minutes. Ignoring the haka did nothing for them.
England 8 NZ 25
Richard Cockerill went eyeball to eyeball with Norm Hewitt in 1997. Photo / Getty Images
The All Blacks were unbeaten in 1997 coming into the Old Trafford test against England. The English were finding their way under new coach Clive Woodward and decided to advance towards the haka. Hooker Richard Cockerill got so close to his opposite man Norm Hewitt, they ended up pushing each other. England's Martin Johnson is said to have whispered to Corckerill after, "What the **** have you done?" However, England surprised with the quality of their performance and rattled the All Blacks at times.
Wales 9 NZ 29
The haka against Wales in 2008 developed into a silent staredown. Photo / Getty Images
The Welsh followed protocol in 2008 and faced the haka on their 10m line. But when the All Blacks finished, Wales didn't move. All of them just stood, staring across at the All Blacks. When the All Blacks realised, they held their ground, too. The crowd loved it. Neither side was going to back down. It went on for more than a minute before referee Jonathan Kaplan persuaded both teams to back down. Wales enjoyed a strong first 40 minutes and led at halftime but were hit by a supremely good All Black effort after the break.
"I thought we had a huge second half, well led by Richie [McCaw] and the leaders, probably the best half of rugby we have played all year," said All Black coach Graham Henry. "It was a good test match, a highly competitive Welsh side playing good rugby stretched us a lot and they will be disappointed with the result, but they should be proud of their advancement in the game. I think they played well and I think they are a very good side. That's been a mark of this [All Black] side all year that they have been under pressure and come through and won games."
France 20 NZ 18
France faced the haka in their 2007 World Cup quarter-final wearing the colours of their flag. Photo / Getty Images
The French were hosting the 2007 World Cup but had to play their quarter-final in Cardiff. They wanted to make a patriotic statement in the way they faced the haka so one-third of the team had red tops, one-third white and one-third blue so they represented the French flag. They also lined up on the halfway line. The All Blacks moved up so both teams could almost touch each other. The French were buzzing after that. They looked to have convinced themselves they could pull off the win everyone said was beyond them. They were right. They played at their passionate best.