Which is a Ambigram?

This is called the words or phrases that can be read on more than one position due to certain symmetry presented letters on its vertical axis, others on its horizontal axis, and others on both.

For example, presents a vertical symmetry, while the D presents the horizontal and the X on both axles. This allows fingers to write on a mirror and read the same word reflected.

Another cause is the use of upper or lower case: in this case, the symmetrical horizontal h would be p, and the u n, while the b would be symmetrical vertically below the d.

An example are the words bum (lazy) and mud (mud), equal in vertical but with different meanings depending on the side of the mirror it reads.

The secret of stutter

That had in common the Emperor Tiberius Claudius. Churchill. Newton and Borges? The four were stutter, speech dysfunction that affects 800,000 people in Spain.

A study by Professor Caries Escera. Department of Psychiatry and Psychobiology of the Autonomous University of Barcelona, has come to the conclusion that the stutter are abnormal representation of speech sounds.
When you hear a phoneme, ie sounds to distinguish the words of one language, the brain response is anomalous.

To produce a sound is necessary to have a good model that allows articulate the right way and people do not stutter and why jam.