Papers by Frederick Kingdom
Psychophysics, 2016
This chapter introduces psychophysics as a methodology, discusses the aims of the book, outlines ... more This chapter introduces psychophysics as a methodology, discusses the aims of the book, outlines how the book is organized, and summarizes its contents. The discussion of aims focuses on the need for a book that provides both the theoretical background and practical tools necessary for analyzing data from psychophysics experiments and the importance of making accessible to both newcomers and seasoned practitioners alike difficult psychophysical concepts and analyses. For the practical tools the chapter introduces the reader to Palamedes, the toolbox of MATLAB software developed by the authors for psychophysical data analysis.
Vision Research, Feb 1, 1999
To determine the relationship between the spatial channels for luminance and shape-from-stereo-di... more To determine the relationship between the spatial channels for luminance and shape-from-stereo-disparity processing we measured disparity modulation sensitivity as a function of disparity spatial frequency for sinusoidal modulations of a field of Gabor micropatterns of differing luminance spatial frequency. We first examine the effects of contrast, spatial bandwidth and element density and show that it is only the last of these which is critical for the shape of the disparity modulation threshold function. We show that the shape of this function depends on the luminance spatial frequency of the surface that is modulated in depth. Specifically, low corrugation frequencies enjoy a greater scale support from the early luminance spatial filters than do high corrugation frequencies. The results are consistent with higher spatial frequency disparity channels receiving a greater input from higher spatial frequency luminance channels.
Journal of Vision, Jul 25, 2013
Scientific Reports, Feb 7, 2019
Previous studies have shown that texture regularity is adaptable, and have suggested that texture... more Previous studies have shown that texture regularity is adaptable, and have suggested that texture regularity might be coded by the peakedness of the underlying spatial frequency distribution. Here we demonstrate the related phenomenon of simultaneous regularity contrast (SRC), in which the perceived regularity of a central texture is influenced by the regularity of a surrounding texture. We presented center-surround arrangements of textures and measured the perceived regularity of the centre, using a centre-only comparison stimulus and a 2AFC procedure. From the resulting psychometric functions the SRC was measured as the difference between test and comparison regularity at the PSE (point of subjective equality). Observers generally exhibited asymmetric bidirectional SRC, in that more regular surrounds decreased the perceived regularity of the centre by between 20-40%, while less regular surrounds increased the perceived regularity of the centre by about 10%. Consistent with previous studies, a wavelet spatial frequency (SF) analysis of the stimuli revealed that their SF distributions became sharper with increased regularity, and therefore that distribution statistics such as kurtosis and SF bandwidth might be used to code regularity. Texture regularity, i.e. the degree of orderliness of element positions in a texture (henceforth, "regularity") is a basic texture property. Regular textures consist of uniform patterns in a cyclical i.e. periodic arrangement 1,2 . Their opposites are textures composed of randomly positioned elements, maximizing their entropy and unpredictability 3 . Different degrees of regularity occur in both natural and artificial surfaces, and convey important information about their structure, etiology and biological function 4,5 . However we know little about how the visual system extracts regularity information. A simple and commonly employed method to construct textures of varying regularity levels is to apply random perturbation ("jitter") independently to the horizontal and vertical element positions in a notional lattice pattern of texture elements, e.g. dots -a larger range of the jitter gives more irregular textures 6-8 . Stimuli constructed using this method have been used to demonstrate that regularity is an adaptable dimension of vision. By measuring the perceived regularity of a pattern following adaptation to a pattern with a different degree of regularity, some studies have demonstrated a "regularity aftereffect" 8 (or, as Yamada et al. put it, a "randomness aftereffect"). Specifically, perceived regularity is reduced after adapting to a more regular pattern 8 and enhanced after adapting to a more irregular one 7 . Varying the element properties between adapt and test textures has revealed that regularity encoding operates on both luminance-as well as contrast-defined elements 8 , and that it is orientation selective but is insensitive to luminance polarity and retinal location 7 . Note that regularity defined in relation to a lattice of element positions is different from the classical "symmetries" -mirror symmetry, radial symmetry, and translational symmetry . Moreover, two of these, mirror-and radial-symmetry, are likely processed by a different class of mechanism to that mediating regularity and translational symmetry. Following on from Ouhnana et al. 's 8 analysis of the Fourier composition of texture regularity, Jennings and Kingdom 14 suggest that information about regularity and translational symmetry is likely carried by the Fourier amplitude spectrum whereas information about mirror-and radial-symmetry is likely carried by the Fourier phase spectrum. This idea is in keeping with the finding that regularity information is mostly preserved under Fourier phase scrambling 15 and that the perception or discrimination of regularity does not require the encoding of the relative position of each texture element 16 . Such a scheme would enable regularity to be encoded rapidly and in parallel at an early stage of vision rather than via a higher level, time-consuming, serial process 17 .
Vision Research, Dec 1, 2001
A compelling percept of three-dimensionality is attainable from a purely motion-defined simulatio... more A compelling percept of three-dimensionality is attainable from a purely motion-defined simulation of a transparent rotating cylinder, referred to as 3-D structure-from-motion (SFM). Interestingly, subjects rarely perceive reversals of the cylinder's direction of rotation when they are introduced. Treue, Andersen, Ando, and Hildreth (Vision Res. 35 (1995) 139-148) have argued that this reflects the visual system's insensitivity to the textural detail on the cylinder's motion surfaces. We have recently shown however that with cylinders made from oriented micropatterns, motion reversals are perceived when the orientations of the micropatterns are different on the cylinder's front/back surfaces, suggesting that the visual system is sensitive to the type of feature in these stimuli (Vision Res. 39 (1999) 881-886). In the present study we extended this finding by testing for feature-sensitivity along other dimensions besides orientation, specifically spatial frequency, colour and luminance polarity. We found that subjects perceived more rotation direction reversals when the front/back surfaces of the cylinder were segregated, as opposed to non-segregated by feature-type, along all of these dimensions except, notably, colour. We also investigated the stage at which the feature-sensitivity is incorporated in 3-D SFM. We reasoned that if 3-D SFM mechanisms were tuned, or labeled for feature-type, swapping of features during the cylinder's rotation would result in illusory reversals in just the feature-segregated condition, whereas if grouping of like-features preceded the formation of 3-D motion surfaces, no such illusory reversals would be expected. We found that feature-swapping resulted in more illusory reversals in the feature-segregated compared to non-segregated conditions, supporting the mechanism tuning, or labeling, hypothesis.
Attention Perception & Psychophysics, May 1, 2001
Under what circumstances is the common motion of a group of elements more easily perceived when t... more Under what circumstances is the common motion of a group of elements more easily perceived when the elements differ in color and/or luminance polarity from their surround? Croner and Albright (1997), using a conventional global motion paradigm, first showed that motion coherence thresholds fell when target and distractor elements were made different in color. However, in their paradigm, there was a cue in the static view of the stimulus as to which elements belonged to the target. Arguably, in order to determine whether the visual system automatically groups, or prefilters, the image into different color maps for motion processing, such static form cues should be eliminated. Using various arrangements of the global motion stimulus in which we eliminated all static form cues, we found that global motion thresholds were no better when target and distractors differed in color than when they were identical, except under certain circumstances in which subjects had prior knowledge of the specific target color. We conclude that, in the absence of either static form cues or the possibility of selective attention to the target color, features with similar colors/luminance-polarities are not automatically grouped for global motion analysis.
Journal of Vision, Jun 13, 2018
Most research on texture density has utilized textures rendered as two-dimensional (2D) planar su... more Most research on texture density has utilized textures rendered as two-dimensional (2D) planar surfaces, consistent with the conventional definition of density as the number of texture elements per unit area. How the brain represents texture density information in the three-dimensional (3D) world is not yet clear. Here we tested whether binocular information affects density processing using simultaneous density contrast (SDC), in which the perceived density of a texture region is changed by a surround of different density. We considered the effect on SDC of two types of binocular information: the stereoscopic depth relationships and the interocular relationships between the center and surround textures. Observers compared the perceived density of two random dot patterns, one with a surround (test stimulus) and one without (match), using a 2AFC staircase procedure. In Experiment 1 we manipulated the stereo-depth of the surround plane systematically from near to far, relative to the center plane. SDC was reduced when the difference in stereo-depth between test center and surround increased. In Experiment 2 we spread the surround dots randomly across a stereodepth volume from small to large volume sizes, and found that SDC was slightly reduced with volume size. The decrease of SDC in both experiments was observed with dense surrounds only, but not with sparse surrounds. In the last experiment we presented center and surround in the same depth plane but dichopticly, monopticly, and binocularly. A strong interocular transfer of SDC was found in the dichoptic condition. Together these results show that texture density processing is sensitive to binocularity.
Journal of the Optical Society of America, May 1, 2001
Are differences in luminance spatial frequency between surfaces that overlap in depth useful for ... more Are differences in luminance spatial frequency between surfaces that overlap in depth useful for surface segmentation? We examined this question, using a novel stimulus termed a dual-surface disparity grating. The dual-surface grating was made from Gabor micropatterns and consisted of two superimposed sinusoidal disparity gratings of identical disparity-modulation spatial frequency and orientation but of opposite spatial phase. Corrugation amplitude thresholds for discrimination of the orientation of the dual-surface grating were obtained as a function of the difference in Gabor (luminance) spatial frequency between the two surfaces. When the Gabor micropatterns on the two surfaces were identical in spatial frequency, thresholds were very high and in some instances impossible to obtain. However, with as little as a 1-octave difference in spatial frequency between the surfaces, thresholds fell sharply to near-asymptotic levels. The fall in thresholds paralleled a change in the appearance of the stimulus from one of irregular depth to stereo transparency. The most parsimonious explanation for this finding is that the introduction of a between-surface luminance spatialfrequency difference reduces the number of spurious cross-surface binocular matches, thus helping to reveal the three-dimensional structure of the stimulus.
Attention Perception & Psychophysics, Dec 1, 1988
Elsevier eBooks, 2016
Signal Detection Theory, or SDT, is probably the most important and influential theoretical frame... more Signal Detection Theory, or SDT, is probably the most important and influential theoretical framework for modeling how perceptual decisions are made in forced-choice tasks. Its central concept is that perceptual decisions are based on a stochastic or probabilistic representation of stimuli inside the brain. The chapter introduces the basic concept of SDT, explains why SDT measures are a useful addition to the psychophysics armory, provides practical details for modeling data using SDT, and explains the theoretical basis of SDT in relation to a range of tasks: 1AFC, 2AFC, M -AFC, same-different, match-to-sample, and oddity. A unique contribution to the SDT literature is the description of how SDT models can be fit to psychometric functions of proportion correct as a function of stimulus intensity, in order to estimate important parameters such as the exponent on the transducer function.
Spatial Vision, 1989
An experiment is described which investigates the spatial determinants of the apparent difference... more An experiment is described which investigates the spatial determinants of the apparent difference in hue between the central grey patches of chromatic 'H' pattern pairs, an effect similar to that first demonstrated by Wright (1969, The Measurement of Colour, Hilger, London) in coloured gratings. The hue difference is shown to be analogous to the brightness difference in achromatic 'H' patterns demonstrated by , Vision Res. 29, 1245-1259). The origin of both effects is argued to be the presence of the corner intersections in the 'H' patterns, which are powerful stimuli for cells with circularly-symmetric, centre-surround organization. It is suggested that the results of the experiment with the chromatic 'H' patterns implicates the operation of cells with a spectrally double-opponent, rather than single-opponent receptive field organization.
Vision Research, 2020
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Journal of Vision, Mar 16, 2010
Perception, Jul 1, 1998
The aim in the experiments was to examine whether the detection of structure-frommotion (SFM) in ... more The aim in the experiments was to examine whether the detection of structure-frommotion (SFM) in noise was facilitated when target and noise were segregated by colour and/or luminance polarity. The SFM target was a rotating 'V-shape' structure simulated with limitedlifetime Gaussian micropatterns and embedded in random-motion noise. Threshold levels of V-shape slant were measured for stimuli in which target and noise were segregated or unsegregated by colour/luminance, and under two conditions, with and without static form cues to the SFM target. The presence or absence of static form cues to the SFM target was manipulated by varying the relative numbers of micropatterns in target and noise. In the absence of static form cues, segregation of target and noise by colour and/or luminance polarity did not facilitate target detection, even when subjects knew which micropatterns belonged to the target. On the other hand, when static form cues were present, segregation improved performance. These results imply that SFM processing is 'form-cue invariant' except when the target form is immediately identifiable in the static view of the stimulus. The significance of the results for understanding the role of colour vision in breaking camouflage and in 'grouping' is discussed. The projected two-dimensional (2-D) motion of a moving object provides the visual system with information about the three-dimensional (3-D) structure of the object, a process referred to as structure-from-motion, or SFM . The recovery of SFM often involves integrating the relative motions of many parts of the object, such as would happen if it were partially camouflaged. In natural visual scenes, however, an object will often differ from its background in other ways besides motion, eg colour, luminance, orientation, scale, binocular disparity. How do these additional dimensions facilitate our ability to extract SFM? In this study we examine whether segregation of an object in noise by colour and/or luminance polarity facilitates the detection of its SFM. The role of colour vision in SFM has not been studied as extensively as in more basic motion tasks, such as the detection of motion direction. Moreover, the role of colour vision in motion processing has been examined primarily at isoluminance, that is, when the stimuli are only defined by colour contrast. Generally, motion perception is weak at isoluminance compared with when luminance based, but there is nevertheless clear evidence for a chromatic input to motion processing (Cavanagh
Vision Research, Mar 1, 2006
Vision Research, 1991
White's effect is a phenomenon in which grey bars replacing segments of the white phase of a squa... more White's effect is a phenomenon in which grey bars replacing segments of the white phase of a square-wave grating appear darker than those replacing segments of the black phase. The direction of the brightness difference is consistent with brightness assimilation rather than with brightness contrast. We present data from two experiments which measure the degree of the brightness difference in stimuli consisting of just three inducing bars and a single grey test bar, as a function of various spatial manipulations of the inducing and test bars. The spatial manipulations were chosen to maxim& the opportunity for assimilation effects to manifest themselves. The results do not support the view that assimilation is an important component of the effect. The data are shown to be consistent with our model of brightness induction in which both a local and a more spatially extensive contrast mechanism operate to produce White's effect.
Elsevier eBooks, 2016
This chapter introduces psychophysics as a methodology, discusses the aims of the book, outlines ... more This chapter introduces psychophysics as a methodology, discusses the aims of the book, outlines how the book is organized, and summarizes its contents. The discussion of aims focuses on the need for a book that provides both the theoretical background and practical tools necessary for analyzing data from psychophysics experiments and the importance of making accessible to both newcomers and seasoned practitioners alike difficult psychophysical concepts and analyses. For the practical tools the chapter introduces the reader to Palamedes, the toolbox of MATLAB software developed by the authors for psychophysical data analysis.
Journal of the Optical Society of America, 2001
How accurately do human observers perceive the properties of an achromatic transparent filter wit... more How accurately do human observers perceive the properties of an achromatic transparent filter with both reflective and transmissive components? To address this question, a novel six-luminance stimulus was employed, consisting of three transparent layer luminances set against three background luminances, which satisfied the conventional constraints of perceptual transparency. In one experiment, subjects adjusted one of the three layer luminances to complete the impression of a uniform transparent disk. It was found that the luminance-based formulation of Metelli's episcotister model and a model based on ratios of Michelson contrasts best predicted the subjects' settings, which were both accurate and precise. In another experiment, pairs of stimuli selected from a range with various values of the adjustable layer luminance were presented in a series of forced-choice trials. A modified implementation of the pair comparisons method was employed to recover the distribution that describes each subject's preference pattern. Results showed that there exists a reasonably wide range of stimuli that give rise to at least some degree of perceived transparency.
Journal of Vision, Dec 5, 2022
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Papers by Frederick Kingdom