Speaking in tongues or glossolalia is a practice among  Pentecostal and Charismatic circles in which individuals speak in what appears to be an unknown language.  Verbal evidence is often accompanied by violent trembling, shaking and a trance-like state of being.  Typical explanation is that they are speaking in “heavenly languages,” perhaps those spoken by angels.

Practitioners believe that the Holy Spirit is speaking through them without use of their conscious faculties. Often someone gives an “interpretation” of what the one engaged glossolalia has said.  Usually interpretation is not to be taken as a literal translation, but rather as a loose explanation of the intent of the message, given directly by the Holy Spirit to the interpreter.

Glossolalia can be traced back to The Book of Acts, Ch. 2.  Supposedly, on the day of Pentecost after the Crucifixion of Jesus when “… there appeared unto them cloven tongues like as of fire,..” divided unto all of the individuals in the “upper room”. They were said to speak in “other tongues as the spirit gave them utterance.”

Speaking in tongues with interpretation.

Material explanation

Attempts to explain the physical and psychological patterns characterized by those Speaking in Tongues have been many. The three most popular explanations are mental illness, hypnosis, and learned behavior.

Mental illness
Psychologists initially thought of glossolalia in pathological terms, thinking that it was because of a mental illness.  Some studies have shown that glossolalia was associated with stable extroversion, and contrary to some theories, completely unrelated to psychopathology.

Hypnosis
Some kind of hypnosis or trance has often been suggested as the explanation for glossolalia, as glossolalia often takes place in trance-like states.  But glossolalia does not require a state of hypnosis or trance.  In one experiment, 12 experienced glossolalists performed with their eyes open and without any trembling, shaking or residual disorientation.  Another study found that “after the initial experience of glossolalia, most Pentecostals speak with tongues as frequently, if not more frequently, alone in private prayer”.  These findings seem to rule out hypnosis by another, although self-hypnosis may play a part.

Learned behavior
Many studies seem to show that glossolalia is “learned behavior”.   What is taught is the ability to produce language-like speech.  This is only a partial explanation, but it is a part that has withstood much testing.  It is possible to train novices to produce glossolalic speech.  One experiment with 60 undergraduates found that 20% succeeded after merely listening to a 60-second sample, and 70% succeeded after training.

ABC News story purporting to prove Speaking in Tongues is the voice of the Holy Spirit