Mesenholl B, Meinhardt G, 2005, "Feature-contrast response and additivity across dimensions" Perception 34 ECVP Abstract Supplement
Feature-contrast response and additivity across dimensions
B Mesenholl, G Meinhardt
When targets contrast with the surround in more than one feature dimension they are usually perceived as more salient (Nothdurft, 2000 Vision Research 40 1183 - 1201). We measured feature-contrast increment thresholds for a wide range of pedestals, and used targets with iso-salient orientation and spatial-frequency contrast as well as single-feature targets. Based on pedestal-versus-increment functions, the feature-contrast response function was estimated with a Naka - Rushton model, as done recently (Motoyoshi and Nishida, 2001 Journal of the Optical Society of America 18 2209 - 2219). Our results show that the salience advantage for redundant targets is remarkable in the vicinity of the detection threshold, but rapidly declines over the next jnds and completely vanishes for highly salient pedestal contrasts. Interestingly, the feature-contrast response saturates for stimulus arrangements that allow grouping to simple figures but continues to rise for random-order spatial arrangements. Further, the saturation point on the feature-contrast response function coincides with the 82% correct point of the psychometric curve for a figure-discrimination task done with the same figures as for pedestal-versus-increment functions measurement. Our results indicate that higher-level processes of figure - ground segregation modulate early feature-specific pathways and the way they interact.
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