I used the word probably to convey that I personally have not done the research. But the TM people have done an extensive amount of scientific studies (some funded by governmental and military sources).
The reason why I wanted to share it was because of my own experience with TM results despite being a life-long an East Coast skeptic.
The mantra repetition is a very simple thing but it does actually have the ability to alter brain wave activity and I believe it has something to do with the cyclical nature of the repeated thought.
You can check out http://www.tm.org/ and other TM related sources for more on the scientific research that they have completed.
Also there are plenty of other reports from successful, creative people who have made TM a part of their daily lives, some for decades e.g. David Lynch, Jerry Seinfeld, Howard Stern, etc.
In addition, in my personal experience there has been a "lucid dreaming" or "inner hallucination" component to my meditations which are sometimes quite visceral in nature....all from just repeating a simple phrase.
That along with its other benefits that I have experienced personally prompted my belief that a mantra based practice is worth trying.