FIFA Women's World Cup in Soccer Finishes Group Stage

The 2015 FIFA Women's World Cup in soccer yesterday completed its group stage of play, with two exciting games within Group E determining the final lineup, heading into the "knockout" round of sixteen.  Originally, I had erroneously reported that each team within a group played the others twice...but, alas, there are only three total games in group stage.  That's good, though, for the United States, which had been for some reason thrown into a group with two 2011 group qualifiers, Australia and Sweden (and the latter had made it all the way to the semifinals) and had managed to be first in that group after playing everyone once.  By contrast, Canada, which is hosting the World Cup this year, had no opponents within their group that had advanced last time, giving them an easier run at it.  The field of teams in 2015 was increased from 16 to 24, and instead of eight coming out of the group stage into the quarterfinal round, this year we have 16 qualifying for the new knockout round, which will be played in various locations across Canada June 20-22.  All eight teams making it out of group stage in 2011 are still in the running (defending champion Japan, runner-up USA, Sweden, France, Germany, England, Brazil, and Australia).  Canada plays against Switzerland on June 21st, while the United States plays against Colombia, a powerhouse in men's international soccer but a fledgling team in the women's sport, on the 22nd.  The tournament will proceed until the final championship game, which will take place on July 5th.

I'm finding the level of play within women's international soccer to be very high, and the games carry a lot of excitement with them.  One thing I noticed, which maybe some of my readers have also, is that there is an enormous amount of yelling back and forth between the players.  Then again, I experience the same phenomenon when watching other women's sports like basketball, lacrosse, volleyball, and softball.  I'm sure that the men playing these sports also yell from time to time, but not anywhere to the same extent that the women do.  I wonder what this discrepancy between the genders means.  Any ideas?