The Ideal Chessplaying Age

Is it really true that the ideal age for an average top chessplayer is 25?

If the answer is "no", it's not far off.

Why? Because the human brain (sorry for the "depressing" fact!) starts to deteriorate when one is 27 years of age. No, it usually isn't immediately noticeable, and of course, not every human being is directly affected by this deterioration, but... its still there, of course.

So is 25 the ideal chessplaying age? If not, it's probably 26. Close enough... right?