The relation of phase noise and luminance contrast to overt attention in complex visual stimuli

Autor(en): Einhaeuser, Wolfgang
Rutishauser, Ueli
Frady, E. Paxon
Nadler, Swantje
Koenig, Peter 
Koch, Christof
Stichwörter: ALLOCATION; attention; eye movements; FIXATIONS; fractals; higher order statistics; NATURAL IMAGES; natural scenes; Ophthalmology; phase noise; saliency; SHIFTS; STATISTICS
Erscheinungsdatum: 2006
Volumen: 6
Ausgabe: 11
Startseite: 1148
Seitenende: 1158
Models of attention are typically based on difference maps in low-level features but neglect higher order stimulus structure. To what extent does higher order statistics affect human attention in natural stimuli? We recorded eye movements while observers viewed unmodified and modified images of natural scenes. Modifications included contrast modulations (resulting in changes to first- and second-order statistics), as well as the addition of noise to the Fourier phase (resulting in changes to higher order statistics). We have the following findings: (1) Subjects' interpretation of a stimulus as a ``natural'' depiction of an outdoor scene depends on higher order statistics in a highly nonlinear, categorical fashion. (2) Confirming previous findings, contrast is elevated at fixated locations for a variety of stimulus categories. In addition, we find that the size of this elevation depends on higher order statistics and reduces with increasing phase noise. (3) Global modulations of contrast bias eye position toward high contrasts, consistent with a linear effect of contrast on fixation probability. This bias is independent of phase noise. (4) Small patches of locally decreased contrast repel eye position less than large patches of the same aggregate area, irrespective of phase noise. Our findings provide evidence that deviations from surrounding statistics, rather than contrast per se, underlie the well-established relation of contrast to fixation.
ISSN: 15347362
DOI: 10.1167/6.11.1

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