Cryptophasia was historically described as a secret language between twins that they invent themselves and that is unintelligible to others. It has been found that some words are indeed invented, but for the most part the words come from the adult language to which they are exposed. At least 90% of the vocabulary in cryptophasia can be directly related to the language of the parents (Bakker, 1987). Some research states that cryptophasia develops when twins experience a notable condition of social isolation.