In rare cases an apparent complete loss of control can be observed, with an individual's behavior tending to exhibit a temporary loss of normal understanding of navigation of one's physical environment. An individual in such a state can cause accidental harm to themselves and to others, and can include behavior such as flailing about or even running into traffic, or, as such a state may not necessarily involve physical movement, may involve induction of a catatonic state or the expression of seemingly random vocalizations i.e. not limited to true speech. This may be caused by a failure to recognize external stimuli for what it is. Stanislav Grof explains this feature: