Glossolalia is an effect in which a person finds themselves involuntarily speaking and/or thinking in nonsensical speech which is structured in a manner that resembles an actual language.   This is often defined by linguists as a melodic and fluid vocalizing of speech-like syllables that lack any readily comprehended meaning.   It is important to note that this effect is distinctly different from the thought disorganization characterized by a schizophrenic's word salad.  
Although there is a litany of research describing this effect in a religious context, this setting is not required; two types of glossolalia have been suggested:  
- Type A (Calm): Occurs in private, mundane settings. Context-dependent with the person self-aware while ‘speaking’ i.e. they can attend to other claims on attention. Appears frequently (daily or several times weekly).
- Type B (Excited): Occurs in public settings as an intense uprush of vocalizations that is a product of a religious altered state. This person is not self-aware and cannot attend to others' claims on attention. Appears occasionally (weekly or less).
During the experience of this effect, it's possible the person who is speaking will be completely unaware that they are speaking in anything but their native language. This can result in confusion and frustration as they struggle to understand why the people around cannot comprehend what they are saying.
Glossolalia is often accompanied by other coinciding effects such as language suppression, catharsis, spirituality enhancement, and delirium. It is most commonly induced under the influence of heavy dosages of hallucinogenic compounds, such as psychedelics, deliriants, and dissociatives.
- Newberg, A. B., Wintering, N. A., Morgan, D., & Waldman, M. R. (2006). The measurement of regional cerebral blood flow during glossolalia: a preliminary SPECT study. Psychiatry Research: Neuroimaging, 148(1), 67-71. | https://doi.org/10.1016%2Fj.pscychresns.2006.07.001
-  Grady, B., & Loewenthal, K. M. (1997). Features associated with speaking in tongues (glossolalia). British Journal of Medical Psychology, 70(2), 185-191. | https://doi.org/10.1111%2Fj.2044-8341.1997.tb01898.x
-  Motley, M. T. (1982). A linguistic analysis of glossolalia: Evidence of unique psycholinguistic processing. Communication Quarterly, 30(1), 18-27. | https://doi.org/10.1080%2F01463378209369424
- Goodman, F. D. (1969). Phonetic analysis of glossolalia in four cultural settings. Journal for the Scientific Study of Religion, 227-239. | https://doi.org/10.2307%2F1384336
- Kavan, H. (2004). Glossolalia and altered states of consciousness in two New Zealand religious movements. Journal of Contemporary Religion, 19(2), 171-184. | https://doi.org/10.1080%2F1353790042000207692