Top-down influence on bottom-up process: the familiarity effect modulates texture segmentation.

This study deals with the familiarity effect (FE), which means that search performance is better when detecting an unfamiliar target in a familiar context compared to the detection performance of a familiar target in an unfamiliar context. In several experiments the spatial and temporal conditions were systematically varied to determine the ones which enable the appearance of the FE. Data were collected as a function of target eccentricity.

Spatial competition on the master-saliency map.

The saliency map model (Itti and Koch, 2000) is a hierarchically structured computational model, simulating visual saliency processing. Iso-feature processing on feature maps and conspicuity maps precedes cross-dimensional signal processing on the master map, where the most salient location of the visual field is selected. This texture segmentation study focuses on a possible spatial structure on the master map.

Electrophysiological correlates of target eccentricity in texture segmentation.

Event-related potentials and behavioural performance as a function of target eccentricity were measured while subjects performed a texture segmentation task. Fit-of-structures, i.e.

Texture segmentation: do the processing units on the saliency map increase with eccentricity?

The saliency map is a computational model and has been constructed for simulating human saliency processing, e.g. pop-out target detection (e.

Spatial distance between target and irrelevant patch modulates detection in a texture segmentation task.

In three texture segmentation experiments a target patch had to be detected. We studied the impact of a task-irrelevant patch in the backward mask on detection performance, and especially the modulating effects of its spatial distance to the target. It was assumed that the signals of the two texture irregularities interact as a function of their spatial distance.

A central performance drop with luminance stimuli requiring spatial integration.

This study reports four experiments that analyzed detection performance for luminance contrasts as a function of retinal eccentricity in order to find further support and explanations for the central performance drop (CPD) in the fovea. In the first experiment, 10 participants (16-37 years of age) had to detect a target patch in a stimulus consisting of bright and dark pixels. Luminance differences between target and context areas were achieved by placing a different number of bright (and dark) pixels in the target and the context area.

Attentional resources and pop-out detection in search displays.

Detecting pop-out targets is often considered as a fast, spontaneous and preattentive process. In most experimental studies, however, the observer's attention is explicitly focused on the detection task. We investigated pop-out detection under varying attention conditions: when pop-out displays were (a) not attended and not relevant, (b) attended and relevant and (c) could be attended but were not relevant.

Automatic texture segmentation in early vision: evidence from priming experiments.

Texture segmentation is usually regarded as a fast, early, automatic, preattentive process. Nevertheless, naive participants in texture segmentation tasks are usually not able to perform the task explicitly when the textures are presented rather briefly (49 ms) and subsequently masked. In two experiments it was investigated whether texture stimuli were, nevertheless, automatically segmented under these conditions.

A 'first stage' central performance drop in a Gabor luminance-modulation detection task.

In an experiment, 20 participants had to detect a backward masked Gabor luminance-modulation target imposed on a field of uniform luminance at varying eccentricities along the horizontal meridian. Different spatial frequencies were used as target modulations. Results for a 7.

Detecting emotional faces and features in a visual search paradigm: are faces special?

In 2 experiments, participants were presented schematic faces with emotional expressions (threatening, friendly) in a neutral-faces context or neutral expressions in an emotional-faces context. These conditions were compared with detection performance in displays containing key features of emotional faces not forming the perceptual gestalt of a face. Supporting the notion of a threat detection advantage, Experiment 1 found that threatening faces were faster detected than friendly faces, whereas no difference emerged between the corresponding feature conditions.

Texture segmentation and visual search for pop-out targets. An ERP study.

"Parallel" visual search and effortless texture segmentation were believed to rely on similar mechanisms until Wolfe [Vis. Res. 32 (1992) 757] demonstrated that efficient visual search and effortless texture segmentation are not always the same thing.

A reversal in the direction of detection asymmetry: effects of spatial density, spatial regularity, and retinal eccentricity.

We analyzed detection asymmetry, using openand closed squares as target and contextelements. It was found that varying density, regularity, and target eccentricity not only can modulate the amount of asymmetry, but also can produce a reversal in the direction of the asymmetry. The results suggest that the different stimuli are processed with different grains of analysis,consisting of in some cases, single elements and their properties and, in other cases, larger units of the stimulus array and more globalproperties.

Detection performance in pop-out tasks: nonmonotonic changes with display size and eccentricity.

We carried out three experiments to investigate detection performance in pop-out tasks and analysed how performance varied as a function of display size (number of elements) and retinal eccentricity of the target. Results showed that when display size was increased from 2 to 81 elements performance first decreased and then increased (replicating Sagi and Julesz, 1987 Spatial Vision 2 39-49). Performance variations differed as a function of eccentricity and often were more pronounced in the periphery than in the foveal area.