A Secret Speech
In homes around the world, some twins grow up sharing more than just birthdays—they invent private languages only they can understand. This mysterious occurrence is called cryptophasia, from the Greek for “secret speech,” and it has been documented in up to 50% of twin pairs during early childhood.
Built from Familiar Sounds
Cryptophasia usually arises from delayed phonological development. The language consists of altered adult words, neologisms, and sound-based expressions. Although it resembles the adult language in origin, it lacks grammar and is often unintelligible to others. Word order is driven by context and emphasis rather than grammar.
Mirrored Minds and Movements
The phenomenon often includes more than speech. Twins like June and Jennifer Gibbons mirrored each other’s actions as well as speech. Another case involved Grace and Virginia Kennedy, born in 1970 in the U.S., who developed a rapid, staccato language understood only by them.
A Language for Two
Experts link cryptophasia to intense twin interaction and limited adult verbal input. Though usually temporary, it can affect language development if not balanced with exposure to conventional speech.
Some twins don’t just finish each other’s sentences—they create whole languages only they can understand.
This rare phenomenon, known as cryptophasia, involves shared speech and even mirrored movements that outsiders often find completely unintelligible…🧵👇 pic.twitter.com/HFn2M29yXI
— Detective Tiger's Stories (@TigerDetective) April 25, 2025