Flicker-light induced visual phenomena: frequency dependence and specificity of whole percepts and percept features.
Flickering light induces visual hallucinations in human observers. Despite a long history of the phenomenon, little is known about the dependence of flicker-induced subjective impressions on the flicker frequency. We investigate this question using Ganzfeld stimulation and an experimental paradigm combining a continuous frequency scan (1-50 Hz) with a focus on re-occurring, whole percepts. On the single-subject level, we find a high degree of frequency stability of percepts. To generalize across subjects, we apply two rating systems, (1) a set of complex percept classes derived from subjects' reports and (2) an enumeration of elementary percept features, and determine distributions of occurrences over flicker frequency. We observe a stronger frequency specificity for complex percept classes than elementary percept features. Comparing the similarity relations among percept categories to those among frequency profiles, we observe that though percepts are preferentially induced by particular frequencies, the frequency does not unambiguously determine the experienced percept.
Department of Empirical and Analytical Psychophysics, Institute for Frontier Areas of Psychology and Mental Health, Wilhelmstraße 3a, 79098 Freiburg, Germany. carsten.allefeld@bccn-berlin.de
Carsten
C
Allefeld
Peter
P
Pütz
Kristina
K
Kastner
Jiří
J
Wackermann
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007088:Illusions / Q000145:classification / Q000523:psychology; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000379:methods; D014796:Visual Perception; D055815:Young Adult