Ecologically valid combinations of first- and second-order surface markings facilitate texture discrimination

Johnson, Aaron P.; Prins, Nicolaas; Kingdom, Frederick A. A.; Baker, Curtis L.

doi:10.1016/j.visres.2007.05.003

Cited by 14 publications

(10 citation statements)

References 37 publications

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“…As can be seen, features obtained from the Intensity Ranklets alone perform better than those obtained from the Variance Ranklets alone. This is in accordance with the findings of psycho-physical studies on the relative importance of the two types of stimuli the filters are designed to detect [9]. The best results are however obtained by combining the two sets of features: the addition of second order information more than halves D1, D3, D4, D5, D6, D8, D9, D11, D16, D17, D18, D20, D21, D25, D26, D27, D28, D29, D33, D36, D78, D87, D92, D95, D101, D102 4 D1, D3, D6, D11, D16, D17, D20, D21, D24, D28, D29, D32, D34, D35, D46, D47, D49, D51, D52, D53, D55, D56, D57, D65, D78, D82, D84, D85, D101, D104 the error rate on three of the datasets.…”

Section: Resultssupporting

confidence: 88%

“…This is motivated both by the importance of second-order stimuli for texture classification [9] and by the results recently obtained by Masotti and Campanini [15], that show that (Intensity) Ranklets compare favourably with Wavelets and Ridgelets in texture classification over a subset of the Vistex and Brodatz databases [5,16]. For ease of comparison, we adopt the same choice of features and datasets as [15], although in combination with a simpler NN classifier as opposed to a Support Vector Machine (SVM).…”

Section: Application: Texture Classificationmentioning

confidence: 99%

“…The human visual system, however, also shows a similar response to contrast or variance modulations (second-order stimuli - Figure 1a). These are thought to be important, for instance, in the perception and discrimination of textures [9].…”

Section: Introductionmentioning

confidence: 99%

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Variance Ranklets: orientation–selective rank features for contrast modulations

Azzopardi¹,

Smeraldi²

2009

Procedings of the British Machine Vision Conference 2009

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We introduce a novel type of orientation-selective rank features that are sensitive to contrast modulations (second-order stimuli). Variance Ranklets are designed in close analogy with the standard Ranklets, but use the Siegel-Tukey statistics for dispersion instead of the Wilcoxon statistics. Their response shows the same orientation selectivity pattern of Haar wavelets on second-order signals that are not detectable by linear filters. To the best of our knowledge, this is the first family of rank filters designed to detect orientation in variance modulations.We validate our descriptors with an application to texture classification over a subset of the VisTex and Brodatz databases. The combination of standard (intensity) Ranklets with Variance Ranklets greatly improves on the performance of Ranklets alone. Comparison with other published results shows that state-of-the-art recognition rates can be achieved with a simple Nearest Neighbour classifier.

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Section: Resultssupporting

confidence: 88%

Section: Application: Texture Classificationmentioning

confidence: 99%

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Variance Ranklets: orientation–selective rank features for contrast modulations

Azzopardi¹,

Smeraldi²

2009

Procedings of the British Machine Vision Conference 2009

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“…Access to multiple visual cues, such as first-and second-order contours, considerably improves performance. When both first- and second-order cues are present, texture segmentation improves (Smith & Scott-Samuel, 2001), but this benefit only occurs when the two cues are correlated in an ecologically valid manner (Johnson, Prins, Kingdom, & Baker, 2007). Perceived contour location is a compromise between the position signaled by second-order texture-defined cues and by other cues such as luminance or motion (Rivest & Cavanagh, 1996).…”

Section: Discussionmentioning

confidence: 99%

Differential effects of exogenous and endogenous attention on second-order texture contrast sensitivity

Barbot¹,

Landy²,

Carrasco³

2012

Journal of Vision

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The visual system can use a rich variety of contours to segment visual scenes into distinct perceptually coherent regions. However, successfully segmenting an image is a computationally expensive process. Previously we have shown that exogenous attention—the more automatic, stimulus-driven component of spatial attention—helps extract contours by enhancing contrast sensitivity for second-order, texture-defined patterns at the attended location, while reducing sensitivity at unattended locations, relative to a neutral condition. Interestingly, the effects of exogenous attention depended on the second-order spatial frequency of the stimulus. At parafoveal locations, attention enhanced second-order contrast sensitivity to relatively high, but not to low second-order spatial frequencies. In the present study we investigated whether endogenous attention—the more voluntary, conceptually-driven component of spatial attention—affects second-order contrast sensitivity, and if so, whether its effects are similar to those of exogenous attention. To that end, we compared the effects of exogenous and endogenous attention on the sensitivity to second-order, orientation-defined, texture patterns of either high or low second-order spatial frequencies. The results show that, like exogenous attention, endogenous attention enhances second-order contrast sensitivity at the attended location and reduces it at unattended locations. However, whereas the effects of exogenous attention are a function of the second-order spatial frequency content, endogenous attention affected second-order contrast sensitivity independent of the second-order spatial frequency content. This finding supports the notion that both exogenous and endogenous attention can affect second-order contrast sensitivity, but that endogenous attention is more flexible, benefitting performance under different conditions.

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“…Access to multiple perceptual cues generally improves performance, and this is the case with 1st- and 2nd-order contours. The presence of both 1st- and 2nd-order cues significantly improves texture segmentation (Smith & Scott-Samuel, 2001), but only when the two cues are correlated in an ecologically valid manner (Johnson, Prins, Kingdom, & Baker, 2007). Perceived edge location is a compromise between the position signaled by texture cues and by other cues such as luminance or motion (Rivest & Cavanagh, 1996).…”

Section: Discussionmentioning

confidence: 99%

Exogenous attention enhances 2nd-order contrast sensitivity

2011

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Natural scenes contain a rich variety of contours that the visual system extracts to segregrate the retinal image into perceptually coherent regions. Covert spatial attention helps extract contours by enhancing contrast sensitivity for 1st-order, luminance-defined patterns at attended locations, while reducing sensitivity at unattended locations, relative to neutral attention allocation. However, humans are also sensitive to 2nd-order patterns such as spatial variations of texture, which are predominant in natural scenes and cannot be detected by linear mechanisms. We assess whether and how exogenous attention—the involuntary and transient capture of spatial attention—affects the contrast sensitivity of channels sensitive to 2nd-order, texture-defined patterns. Using 2nd-order, texture-defined stimuli, we demonstrate that exogenous attention increases 2nd-order contrast sensitivity at the attended location, while decreasing it at unattended locations, relative to a neutral condition. By manipulating both 1st- and 2nd-order spatial frequency, we find that the effects of attention depend both on 2nd-order spatial frequency of the stimulus and the observer’s 2nd-order spatial resolution at the target location. At parafoveal locations, attention enhances 2nd-order contrast sensitivity to high, but not to low 2nd-order spatial frequencies; at peripheral locations attention also enhances sensitivity to low 2nd-order spatial frequencies. Control experiments rule out the possibility that these effects might be due to an increase in contrast sensitivity at the 1st-order stage of visual processing. Thus, exogenous attention affects 2nd-order contrast sensitivity at both attended and unattended locations.

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Ecologically valid combinations of first- and second-order surface markings facilitate texture discrimination

Cited by 14 publications

References 37 publications

Variance Ranklets: orientation–selective rank features for contrast modulations

Variance Ranklets: orientation–selective rank features for contrast modulations

Differential effects of exogenous and endogenous attention on second-order texture contrast sensitivity

Exogenous attention enhances 2nd-order contrast sensitivity

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