The Ganzfeld experience—A stably inducible altered state of consciousness: Effects of different auditory homogenizations

In the Ganzfeld technique, the visual and auditory perceptual fields are homogenized. After a short exposure to completely unstructured sensory input, participants transit into an altered state of consciousness. Visual homogenization is typically accomplished by a combination of goggles and bright light; auditory homogenization is accomplished by the presentation of unstructured auditory noise via headphones. The induced state is phenomenologically similar to a transition state between wakefulness and sleep, characterized by alterations in attentiveness, perception, and awareness, as well as by a compressed sense of time. Due to these replicable features of the Ganzfeld-induced state, it can be used within empirical research on the neuronal underpinnings of altered states phenomena. After a historic overview, here, we present data from a study on the stability of the subjectively experienced effects induced under different auditory homogenization conditions. In a fully randomized within-subject design (n = 24), we tested for the effects of three different auditory noise conditions: (1) violet, (2) white, and (3) brown noise. The combination of a standardized psychometric assessment, ratings on subjective time perception, as well as open reports prove the Ganzfeld-induced effects as being stable and effects within each participant as highly replicable, and therefore well suited for experimental purposes. Finally, the subjective experiences elucidated by the Ganzfeld technique are discussed within the framework of predictive coding and how changes in the interaction of top-down and bottom-up brain mechanisms could lead to the observed phenomenology.