title: Top-down preparation modulates visual categorization but not subjective awareness of objects presented in natural backgrounds.
abstract: Top-down processes are widely assumed to be essential in visual awareness, subjective experience of seeing. However, previous studies have not tried to separate directly the roles of different types of top-down influences in visual awareness. We studied the effects of top-down preparation and object substitution masking (OSM) on visual awareness during categorization of objects presented in natural scene backgrounds. The results showed that preparation facilitated categorization but did not influence visual awareness. OSM reduced visual awareness and impaired categorization. The dissociations between the effects of preparation and OSM on visual awareness and on categorization imply that they influence at different stages of cognitive processing. We propose that preparation influences at the top of the visual hierarchy, whereas OSM interferes with processes occurring at lower levels of the hierarchy. These lower level processes play an essential role in visual awareness.
authors.affiliation: Department of Psychology, University of Turku, Assistentinkatu 7, 20014 Turku, Finland. Electronic address: mika.koivisto@utu.fi.
authors.forename: Mika
authors.initials: M
authors.lastname: Koivisto
authors.affiliation: Department of Psychology, University of Turku, Assistentinkatu 7, 20014 Turku, Finland.
authors.forename: Ella
authors.initials: E
authors.lastname: Kahila
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001364:Awareness / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology; D010470:Perceptual Masking / Q000502:physiology; D011930:Reaction Time; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Attention; Awareness; Categorization; Masking