Qwiss I’m not sure. I had a brief read around to see if any studies had been done and from what I read it didn’t seem there was a significant and conclusive difference between stutter and normal penalties. Wasn’t comprehensive though so I may have missed something.
The whole point of a penalty is that it gives the attacking team the upper hand. From the outset you have one over on the keeper; you have the advantage of knowing where you’re going and he doesn’t.
All the stutter pen does is level the playing field. You’re now introducing doubt to your own action and levelling the playing field to the benefit of the keeper. Your technique and confidence has to be spot on in a split second to overcome the disadvantaged position you’ve not put yourself in. They’re also generally a bit less powerful due to the run up which also makes it easier for the keeper to cover the ground to it. It’s madness and I can’t believe players persist with it.
I’m of the opinion it’s more a form of attention-seeking, showboating behaviour than anything else.