Experiments on the Fehrer-Raab effect and the 'Weather Station Model' of visual backward masking.
The Fehrer-Raab effect (simple reaction time is unaffected by metacontrast masking of the test stimulus) seems to imply that a stimulus can trigger a voluntary reaction without reaching a conscious representation. However, it is also possible that the mask triggers the reaction, and that the masked test stimulus causes a focussing of attention from which processing of the mask profits, thus reaching conscious representation earlier. This is predicted by the Weather Station Model of visual masking. Three experiments tested this explanation. Experiment 1 showed that the masked test stimulus caused a temporal shift of the mask. Experiment 2 showed that the reaction in the Fehrer-Raab effect was not exclusively triggered by a conscious representation of the test stimulus: the mask was involved in evoking the reaction. Experiment 3 again revealed a temporal shift of the mask. However, the shift was only about half as large as the Fehrer-Raab effect. The psychometric functions suggested that the observers used two different cues for their temporal order judgments. The results cast doubts on whether judged temporal order yields a direct estimate of the time of conscious perception. Some methodological alternatives are discussed.
Neumann
Odmar
O
Department of Psychology, Bielefeld University, P.O. Box 10 01 31, 33501, Bielefeld, Germany. odmar.neumann@uni-bielefeld.de
Scharlau
Ingrid
I
D003071:Cognition; D006801:Humans; D010470:Perceptual Masking; D010865:Pilot Projects; D011589:Psychology, Experimental / Q000379:methods*; D011594:Psychometrics; D011930:Reaction Time; D014796:Visual Perception