Telepathy, the ability to mentally communicate with other people or read their thoughts, was definitively proven not to exist hundreds of years before the events of Ethan of Athos. However, through a long-duration genetics experiment by Faz Jahar on Eta Ceta, the ability was created approximately at the time that Miles Vorkosigan was born.
The work was based on some kind of natural variant found in an impoverished, mad, migrant witch-woman. The human pineal gland, located in the head, was modified extensively to create a sensory organ unlike any previous human one. The ability had to be turned on by ingesting large quantities of tyramine; once the body had processed the excess, the ability switched off. It also lay latent until puberty. The results of using the ability were not 100% reliable - some people's thoughts could not be read by Terrence; others could not be read by Janine.
- Ethan of Athos, particularly chapter 8