It has been suggested (Tadmor and Tolhurst, 1994 Vision Research34 541–554) that the psychophysical task of discriminating changes in the slope of the amplitude spectrum of a complex image may be similar to detecting differences in the degree of blur. It has also been suggested that human observers may perform this discrimination by detecting changes in the effective contrast within single narrow spatial-frequency bands, rather than by detecting changes in the slope per se which would involve the use of contrast information across many different frequency bands. To distinguish between these two possibilities, we have developed an experiment where observers were asked to discriminate changes in the spectral slope while different amounts of random contrast variation were introduced, with the purpose of disrupting their performance. This disruptive effect was designed to be particularly manifest if the observer really was performing a single-frequency-band contrast discrimination but to be unnoticeable if the observer was discriminating the change of slope per se. Our results imply that the observers do not usually detect changes in contrast in just one narrow spatial-frequency band when they discriminate changes in the slope of the amplitude spectrum. Rather, they must compare contrast between bands or, at least, they use contrast information from more than one band. However, for edge-enhanced (whitened) pictures, there is some evidence to suggest that observers rely on contrast changes in only a limited low-spatial-frequency band.
Get full access to this article
View all access options for this article.
References
1.
AttickJ J, 1992“Could information theory provide an ecological theory for sensory processing?”Network3231–251.
2.
AttickJ JRedlichA N, 1992“What does the retina know about natural scenes?”Neural Computation4196–210.
3.
BakerG EThompsonI DKrugKSmythDTolhurstD J, 1998“Spatial frequency tuning and geniculocortical projections in the visual cortex (areas 17 and 18) of the pigmented ferret”European Journal of Neuroscience102657–2668.
4.
BarlowH B, 1961“Possible principles underlying the transformation of sensory messages”, in Sensory Communication Ed. RosenblithW A (Cambridge, MA: MIT Press)pp 217–274.
5.
BlakemoreCCampbellF W, 1969“On the existence of neurons in the human visual system selectively sensitive to the orientation and size of retinal images”Journal of Physiology (London)203237–260.
6.
BracewellR N, 1986The Fourier Transform and Its Applications (New York: McGraw-Hill).
7.
BrelstaffG JTrościankoT, 1992“Information content of natural scenes: Implications for neural coding of color and luminance”SPIE—Human Vision, Visual Processing and Digital Display1666302–309.
8.
BurtonG JMoorheadI R, 1987“Color and spatial structure in natural scenes”Applied Optics26157–170.
9.
CampbellF WKulikowskiJ J, 1966“Orientation selectivity of the human visual system”Journal of Physiology (London)187437–445.
10.
CampbellF WRobsonJ G, 1968“Application of Fourier analysis to the visibility of gratings”Journal of Physiology (London)197551–566.
11.
CarlsonC R, 1978“Thresholds for perceived image sharpness”Photographic Science and Engineering2269–71.
12.
De ValoisR LAlbrechtD GThorellL G, 1982“Spatial frequency selectivity of cells in macaque visual cortex”Vision Research22545–559.
13.
EdwardsA W F, 1976Likelihood (Cambridge, UK: Cambridge University Press).
14.
FieldD J, 1987“Relations between the statistics of natural scenes and the response properties of cortical cells”Journal of the Optical Society of America A42379–2394.
15.
FieldD J, 1989“What the statistics of natural images tell us about visual coding”SPIE—Human Vision, Visual Processing and Digital Display1077269–276.
16.
FoleyJ M, 1994“Human luminance pattern–vision mechanisms: Masking experiments require a new model”Journal of the Optical Society of America A111710–1719.
17.
GoodmanJ W, 1968Introduction to Fourier Optics (New York: McGraw-Hill).
18.
HamerlyJ RDvorjakC A, 1981“Detection and discrimination of blur in edges and lines”Journal of the Optical Society of America71448–452.
19.
van HaterenJ Hvan der SchaafA, 1998“Independent component filters of natural images compared with simple cells in primary visual cortex”Proceedings of the Royal Society, Series B265359–366.
20.
HeegerD J, 1992“Normalization of cell responses in cat striate cortex”Visual Neuroscience9181–197.
21.
HessR FPointerJ SWattR J, 1989“How are spatial filters used in the fovea and parafovea?”Journal of the Optical Society of America A6329–339.
22.
KnillD CFieldD JKerstenD, 1990“Human discrimination of fractal images”Journal of the Optical Society of America A71113–1123.
23.
KretzmerE R, 1952“Statistics of television signals”Bell Systems Technical Journal31751–763.
24.
LaughlinS B, 1981“A simple coding procedure enhances a neuron's information capacity”Zeitschrift für Naturforschung, Section C: Biosciences36910–912.
25.
LeggeG E, 1981“A power law for contrast discrimination”Vision Research21457–467.
26.
LeggeG EFoleyJ M, 1980“Contrast masking in human vision”Journal of the Optical Society of America701458–1471.
27.
MovshonJ AThompsonI DTolhurstD J, 1978“Spatial and temporal contrast sensitivity of neurones in areas 17 and 18 of the cat's visual cortex”Journal of Physiology (London)283101–120.
28.
NachmiasJSansburyR V, 1974“Grating contrast: Discrimination may be better than detection”Vision Research141039–1042.
29.
OlshausenBFieldD J, 1997“Sparse coding with an overcomplete basis set: A Strategy employed by VI?”Vision Research373311–3325.
30.
PárragaC ABrelstaffG JTrościankoTMoorheadI, 1998“Color and luminance information in natural scenes”Journal of the Optical Society of America A15563–569.
31.
PárragaC ATolhurstD JTrościankoT, 2000“The human visual system is optimised for processing the spatial information in natural visual images”Current Biology1035–38.
32.
PeliE, 1990“Contrast in complex images”Journal of the Optical Society of America A72032–2040.
33.
PelliD GZhangL, 1991“Accurate control of contrast on microcomputer displays”Vision Research311337–1350.
34.
RohalyA MAhumadaA JWatsonA B, 1997“Object detection in natural backgrounds predicted by discrimination performance and models”Vision Research373225–3235.
35.
ShapleyR MEnroth-CugellC, 1984“Visual adaptation and retinal gain controls”Progress in Retinal Research3263–346.
36.
SrinivasanM VLaughlinS BDubsA, 1982“Predictive coding: A Fresh view of inhibition in the retina”Proceedings of the Royal Society of London, Series B216427–459.
37.
TadmorYTolhurstD J, 1994“Discrimination of changes in the second-order statistics of natural and synthetic images”Vision Research34541–554.
38.
TadmorYTolhurstD J, 2000“The Difference-of-Gaussians receptive-field model and the contrasts in natural scenes”Vision Research403145–3157.
39.
TolhurstD JBarfieldL P, 1978“Interactions between spatial frequency channels”Vision Research18951–958.
40.
TolhurstD JTadmorY, 1997a“Discrimination of changes in the slopes of the amplitude spectra of natural images: Band limited contrast and psychometric functions”Perception261011–1025.
41.
TolhurstD JTadmorY, 1997b“Band-limited contrast in natural images explains the detectability of changes in the amplitude spectra”Vision Research373203–3215.
42.
TolhurstD JTadmorYArthursG, 1996“The detection of changes in the amplitude spectra of natural images is explained by a band-limited local contrast model”SPIE—Human Vision and Electronic Imaging2657154–165.
43.
TolhurstD JTadmorYTang Chao, 1992“Amplitude spectra of natural images”Ophthalmic and Physiological Optics12229–232.
44.
TolhurstD JThompsonI D, 1981“On the variety of spatial frequency selectivities shown by neurons in area 17 of the cat”Proceedings of the Royal Society of London, Series B213183–199.
45.
WalshGCharmanW N, 1988“Visual sensitivity to temporal change in focus and its relevance to the accommodation response”Vision Research281207–1221.
46.
WatsonA BRobsonJ G, 1981“Discrimination at threshold-labelled detectors in human vision”Vision Research211115–1122.
47.
WattR JMorganM J, 1983“The recognition and representation of edge blur: Evidence for spatial primitives in human vision”Vision Research231465–1477.
