Glossolalia, or speaking in tongues, is the practice of some religious people of uttering unintelligible, probably meaningless, speech-like sounds, usually during periods of intense religious worship. Practitioners often describe positive emotions while speaking in tongues. Although mainly associated with Christianity, it also is observed in other cultures and religions.
Glossolalia is distinct from xenoglossy, being the ability to use an intelligible language that could not be acquired through natural means. Neither term precisely describes being understood simultaneously in different languages.
Glossolalia is argued to be an indicator of a person having been "baptized in Holy Spirit." The practice among Christians is derived from the supposed xenoglossy in the Bible books of Acts 2:4 and 1 Corinthians, where the apostles are said to have spoken in tongues in immediate response to the Holy Spirit acting upon them.
Paul the Apostle argues against praying in this manner because no human can understand what is said. 1 Corinthians 14:15-16 There is no instance in the Bible that resembles what is now called speaking in tongues. Because people speaking in tongues are not intelligable, they do not fulfill biblical signs that we might expect from the New Testament.
The practice is most common among evangelical fundamentalist Christians, particularly within the pentecostal church. The practice among Christians was revived in modern times by preachers such as Kenneth Hagin and Kenneth Copeland in the mid-seventies as part of the "Pentecostal revival." Some, like Hagin, took the practice a step further by engaging in even stranger acts "under the influence of the Spirit." At one sermon, Mr. Hagin was speaking of being "drunk in the Spirit", when he suddenly started acting as though he were staggering drunk-laughing, slurring his words, and stumbling around the room, an action that the audience members immediately started mimicking. On other occasions, Mr. Hagin began hissing like a snake, after which the audience of course immediately started to also make animal sounds, with some lowing like cows, some barking, and some squealing like pigs.
Glossolalia is often described as a "prayer language" or "angelic language." It is said by many evangelicals that glossolalia can be used to pray when you're not quite sure what to pray, or when you wish to speak to God privately- ignoring the fact that if God is omniscient, he doesn't need prayer at all, let alone prayer in a "language" that even the believer does not understand. Some say that it is a language that Satan cannot understand. It is also interesting to note that if it is, indeed, an "angelic language", then angels are so advanced as to have no need of such complex languages as humans use, since most glossolalia seems to consist of the same half-dozen or so syllables repeated over and over again. "SH" and "LA" sounds seem to make up a majority of this "speech", with many extensively rolled "R"s thrown in.
Notably, modern glossolalia does not mirror the practice as stated in the Bible, wherein listeners of various languages are said to have understood the apostles as if they were being spoken to in their own language. Acts 2:6-8 Rather, the sounds uttered by modern Christians when "speaking in tongues" are not understood by anyone in any conventional sense. Sometimes a person with a spiritual gift of interpretation can "translate" the speech into a standard language as another person is speaking in tongues. There is no evidence the translated message has any relationship to the original glossolalia content. 
Most scientists consider the phenomena to be explainable based on brain activity, possibly related to an altered states of consciousness, trance, self-hypnosis or simply a learned behaviour. Glossolalia occurs in many religions and cultures around the world. The utterances in Christian and non-Christian sources did not have any observable difference.  The (lack of) structure is very dissimilar to any known language. Speaking in tongues is associated with strong emotion.
Brain activity studies showed a decrease in frontal lobe activity (an area used in intentional activities). The expressive parts of the language area of the brain was unaffected and is perhaps not used. 
With practice, non-religious people have been able to produce a similar series of utterances.  Glossolalia may therefore be a learned behaviour.
- ↑ Yuriy, Ten hard questions about speaking in tongues, September 30, 2013
- ↑ Felicitas D. Goodman, Speaking in Tongues: A Cross-Cultural Study of Glossolalia, 2008
- ↑ Andrew B. Newbergemail et al., The measurement of regional cerebral blood flow during glossolalia: A preliminary SPECT study, 2006
- ↑ Spanos, Nicholas P.; Cross, Wendy P.; Lepage, Mark; Coristine, Marjorie, Glossolalia as learned behavior: An experimental demonstration. Journal of Abnormal Psychology, Vol 95(1), Feb 1986, 21-23. doi: 10.1037/0021-843X.95.1.21