And then there was light in the ganzfeld: clarifying the methods, experiences, and modulating factors of hallucinations and decays.

Abstract

A Ganzfeld is a homogeneous, unstructured visual field that is known to induce visual hallucinations. Aside from visual percepts emerging in participants' awareness, Ganzfeld viewing is characterized by decays of color and brightness. The studies dedicated to this topic from the 20^th century have focused on these decays, although they have been reported in a confusing way, with different terms for these decaying experiences. This paper synthesizes the current state of the Ganzfeld literature going back to the 1930s with the purpose of clarifying the terminology of the phenomena that have largely retained their mysterious aspects. We built a Ganzfeld space to study the phenomenology without the restricted feeling of a confined space that translucent Ganzfeld goggles cause. Employing a multi-method approach, we combined quantitative and qualitative measures to better grasp the number, kind and temporal dynamics of the experienced phenomena as well as their experiential characteristics. We offer more insight into the different kinds of visual percepts that emerge in participants' awareness, induced by the Ganzfeld, and we identified three distinct types of decays of color and brightness. Based on previously used terminology, we propose to employ the terms 'fade-out', 'black-out' and 'blank-out', and present both the prevalence as well as the qualitative characteristics of these decays. Finally, we shed some light onto the role of eye movements and blinks on the experienced phenomena. All of this is relevant groundwork to be able to study the dynamics of different Ganzfeld experiences, in relation to different states of consciousness and their neural correlates in future work.