Human Perception of Objects

Transcription

1 Human Perception of Objects Early Visual Processing of Spatial Form Defined by Luminance, Color, Texture, Motion, and Binocular Disparity David Regan York University, Toronto University of Toronto Sinauer Associates, Inc., Publishers Sunderland, Massachusetts

2 Contents CHAPTER 1 How Do We See Objects? Conceptualizing the Question and Tackling It 1 Was the Evolution of Our Visual System Driven by the Evolution of Natural Camouflage? 2 The Organization of This Book 4 Visually Guided Goal-Directed Action 6 Psychophysical Methods and Psychophysical Models 8 Psychophysical methods and data 8 Information 23 Class A and Class B observations 25 Psychophysics is not physiology: Mathematical versus structural models of a system 26 The sets of filters hypothesis 30 Rationale for the sets of filters hypothesis 33 Modularity 35 Evidence for quasi-independent processing 35 Opponent processing 36 Regional binding and boundary detection models 39 Inter-Observer Variability and Classification Schemes 40 Disordered Vision 42 Spatial Discriminations, Hyperacuities, and Impostors 44 Figural Aftereffects 48 vii

3 viii Contents Contrast Sensitivity Functions of Human Observers, and the Description of a Stimulus Pattern in Terms of Its Power Spectrum and Its Phase Spectrum 53 The contrast sensitivity function 53 Two alternative (and complementary) ways of describing a spatial pattern 57 Mexican-Hat Receptive Fields 61 CHAPTER 2 Luminance-Defined Form 65 Preamble 65 Detection of Luminance Spatial Contrast and the Contrast Sensitivity Function for Luminance-Defined Form 66 Detection of a nonrepetitive local stimulus 66 Detection of the spatial periodicity of a static grating 67 Effects of temporal frequency on grating contrast sensitivity I: Foveal vision 71 Effects of temporal frequency on grating contrast sensitivity II: Peripheral vision 74 Channels for Luminance-Defined Form and Contrast Gain Control 75 Adaptation, masking, and other evidence for channels 75 The dipper effect 91 Demodulation 93 Positional Discrimination, Width Discrimination, Separation Discrimination, and Spatial Frequency Discrimination for Luminance- Defined Form 98 Positional discrimination: Vernier acuity and bisection acuity 98 Bar width discrimination and bar separation discrimination 107 Spatial-frequency discrimination 108 Orientation Discrimination, Angle Discrimination, and Curvature Discrimination 115 Orientation discrimination for luminance-defined form 115 Discrimination of implicit orientation 123 Angles 131 Curvature 135 Psychophysical Models of the Processing of Luminance-Defined Form along One Dimension 140

4 Contents ix Overview: Local signals and comparisons of signals from distant locations 140 The ideal observer 142 Early filters 143 The Fourier analysis model 143 Centroids, spatial derivatives, and zero-crossings 144 Line-element models 151 Viewprint 153 Multipoles 154 Coincidence detectors 156 Models of bisection acuity 169 Models of curvature discrimination 170 Shortcomings 170 From One to Two Dimensions 171 Bessel function targets 171 Orthogonal gratings: Discrimination and masking 173 Aspect-ratio discrimination and the aspect-ratio aftereffect 174 Short-term memory and attention: What roles do they play in visual discriminations? 184 Disordered Processing of Luminance-Defined Form in Patients 191 Contrast sensitivity loss that is selective for spatial frequency and orientation, and is caused by a neurological disorder 191 Degraded spatial-frequency discrimination caused by a neurological disorder 203 Contrast sensitivity loss that is selective for spatial frequency and orientation, and is caused by refractive error 203 CHAPTER 3 Color-Defined Form 207 Preamble 207 The Concept of Equiluminance and Caveats 209 Can we see spatial form that is rendered visible by chromatic contrast alone? 209 The distinction between the processing of achromatic contrast, monochromatic contrast, and chromatic contrast: Some hypotheses 211 CIE luminance and sensation luminance 219 The concept of equiluminance 220

5 x Contents Heterochromatic flicker photometry : A candidate procedure for silencing the achromatic system 220 The minimally distinct border : A candidate procedure for silencing the achromatic system 223 Minimal motion : A candidate procedure for silencing the achromatic system 223 Do all methods of measuring luminance give the same result? 224 The titration method : A candidate procedure for silencing the achromatic system 224 The effect of temporal frequency on the sensitivities of the chromatic and achromatic systems 228 Temporal summation characteristics for the chromatic and achromatic systems: Bloch s law for color and for luminance 233 The titration method used to determine the contrast sensitivity of the chromatic contrast system 234 But what if our model is wrong? 237 Detection of Color-Defined Form: Contrast Sensitivity Functions for Color-Defined Form 245 Channels for Color-Defined Form 250 Orientation Discrimination for Color-Defined Form 253 Positional Discrimination, Width Discrimination, Separation Discrimination, and Spatial Frequency Discrimination for Color-Defined Form 255 Positional discrimination 255 Bar width and bar separation discrimination 255 Spatial frequency discrimination 256 Aspect Ratio Discrimination for Two-Dimensional Color-Defined Form 256 Disordered Processing of Color-Defined Form in Patients 256 Psychophysical Models of the Processing of Color-Defined Form 258 Models based on an achromatic contrast system with a V λ spectral sensitivity 259 Models framed in terms of two or more parallel spatial filters sensitive to monochromatic contrast 262 CHAPTER 4 Texture-Defined Form 267 Preamble 267

6 Contents xi Detection of Texture-Defined Form 268 Channels for Texture-Defined Form 274 Orientation Discrimination for Texture-Defined Form 277 Positional Discrimination, Width Discrimination, Separation Discrimination, and Spatial Frequency Discrimination for Texture-Defined Form 279 Positional discrimination 279 Bar-width and bar-separation discrimination 281 Spatial-frequency discrimination 282 Aspect Ratio Discrimination for Two-Dimensional Texture-Defined Form 284 Disordered Processing of Texture-Defined Form in Patients 284 Psychophysical Models of the Processing of Texture-Defined Form: Local Signals; Distant Comparisons of Global Features; Distant Comparisons of Local Features 288 CHAPTER 5 Motion-Defined Form 295 Preamble 295 Helmholtz 295 Two kinds of visual information caused by self-motion, each of which can be used in two ways 297 What is it about motion parallax that breaks camouflage? 298 Detection of Motion-Defined Form 301 Two ways in which motion parallax can render visible a spatial form 301 Two kinds of motion contrast 301 Detection of spatial form defined by shearing motion; contrast sensitivity functions for motion-defined form 304 Spatial summation for motion-defined form 306 Temporal summation for motion-defined form 307 Different rates of retinal image expansion: A possible aid in segregating an object s retinal image from the retinal image of the object s surroundings 309 Channels for Motion-Defined Form 310 Orientation Discrimination for Motion-Defined Form 312

7 xii Contents Positional Discrimination, Width Discrimination, Separation Discrimination, and Spatial-Frequency Discrimination for Motion-Defined Form 314 Positional discrimination: High precision for discriminating relative position co-exists with low accuracy for estimating absolute position 314 Bar-width and bar-separation discrimination 316 Spatial-frequency discrimination for motion-defined form 316 Aspect Ratio Discrimination for Two-Dimensional Motion-Defined Form: Local Signals and Distant Comparisons 316 Spatial Processing of Form Defined by Short-range Apparent Motion 317 The Relation between Motion-Defined Form and Relative Depth 320 Two kinds of relative motion information about relative depth 320 Psychophysical evidence that motion-sensitive mechanisms are segregated with respect to relative disparity 322 Experimental comparison of the effectiveness of motion parallax and binocular disparity as stimuli for the perception of spatial structure in the depth dimension 324 Disordered Processing of Motion-Defined Form in Patients 324 Psychophysical Models of the Processing of Motion-Defined Form: Local Signals and Distant Comparisons 327 Detection of local motion 327 Processing of motion-defined form by comparing the local velocities in two separate regions I: Boundaries defined by compressive/expansive motion 330 Processing of motion-defined form by comparing the local velocities in two separate regions II: Boundaries defined by shearing motion 333 Resolution of a relative velocity vector into orthogonal components by the two kinds of relative-motion filter 333 Processing of motion-defined form on the basis of local signals 334 CHAPTER 6 Disparity-Defined Form 343 Preamble 343 Corresponding Points, the Horopter, Relative Disparity, and the Correspondence Problem 346

8 Contents xiii The geometrical theory of stereopsis 346 The empirical horizontal point horopter and the psychophysics of absolute and relative disparity 348 The correspondence problem 352 Does the Visual System Contain Different Mechanisms for Processing Static (Positional) Disparity and for Processing a Rate of Change of Disparity? 353 Richards Pool Hypothesis of Stereopsis 354 Do Laboratory Data Obtained with Random-Dot Stereograms Give Us the Correct Impression of How the Visual System Processes Stereoscopic Depth in Everyday Conditions? 357 Detection of Disparity-Defined Form 357 The disparity-contrast sensitivity function for cyclopean gratings 358 The effect of luminance contrast on stereoacuity 359 Channels for Disparity-Defined Form 360 Cyclopean channels 360 What is the relation between the early spatial filtering of luminance information and the spatial filtering of disparity information? 361 A Comparison of the Temporal Characteristics of Visual Processing before and after Binocular Convergence 362 Selectivity for temporal frequency 363 Temporal integration 364 Orientation Discrimination for Disparity-Defined Form 367 Positional Discrimination, Width Discrimination, Separation Discrimination, and Spatial-Frequency Discrimination for Disparity-Defined Form 367 Positional discrimination 368 Bar-width and bar-separation discrimination 369 Spatial-frequency discrimination 370 Aspect-Ratio Discrimination for Two-Dimensional Disparity-Defined Form 370 Stereopsis at Isoluminance 372 Disordered Processing of Disparity-Defined Form in Patients 372 Psychophysical Models of the Processing of Disparity-Defined Form 373 The correspondence problem again 373 Modeling the processing of disparity-defined form 374

9 xiv Contents CHAPTER 7 Integration of the Five Kinds of Spatial Information: Speculation 375 Preamble 375 Independence of Spatial Discriminations 377 Spatial Filters 378 Similarity of Orientation and Spatial-Frequency Discrimination Thresholds for the Five Kinds of Form 380 Registration 382 APPENDIX A Systems Science and Systems Analysis 385 Signal Analysis Is Not Systems Analysis 385 The role of signal analysis 386 Basis functions 386 Human-Designed Systems: Linear Systems and the Wide and Wild World of Nonlinear Systems 389 Human-designed systems: Functional versus structural analysis 389 Linear systems 391 The creation of a linear system from nonlinear parts 393 The sequence of subsystems within a system 394 Nonlinear behavior 395 What is nonlinearity good for? What use is linearity? 399 To What Extent Are Methods Developed for Studying Human-Designed Systems Valid for the Study of Biological Systems? 400 Levels of Difficulty 402 A Simplifying Assumption: Sets of Filters 403 APPENDIX B Outline of Fourier Methods and Related Topics 405 Fourier Series 405 The Fourier Transform 415 Localized Images: Spatial-Frequency Description along One Dimension 416

10 Contents xv Can Complex Patterns Be Synthesized by Superimposing Sinusoidal Gratings? 420 Localized Images: Spatial-Frequency Description along Two Dimensions 422 Modulation 423 Demodulation 426 Autocorrelation, Cross-correlation, and Convolution 427 Autocorrelation 428 Cross-correlation 428 Convolution 429 Coherent Light, Incoherent Light, Interference, and Diffraction 430 Huygens theory of secondary wavelets 430 Interference of light 433 Interference fringes on the retina 434 The optical quality of the eye 435 Coherence, coherence length, coherence time, and incoherence 436 Diffraction and the Airy disc 439 APPENDIX C Imaging 441 Lens Design and the Geometrical Theory of Aberrations 441 Cardinal Points 444 Gaussian Optics 445 Fourier Optics 446 The historical background 447 The optical transfer function 448 Modulation transfer functions of real lenses: Relevance to vision research 449 Is Human Visual Acuity Limited by Diffraction, or by the Eye s Imaging Performance? 452 The Development of the Eye s Optics through Early Life: Why Are We Not All Short-sighted or Long-sighted? 453 Why Is the Retina Backwards? 455

11 xvi Contents APPENDIX D Opponent-Process and Line-Element Models of Spatial Discriminations 457 APPENDIX E Rectification, Linearizing ON and OFF Physiological Systems, and Clynes Theory of Physiological Rein Control 461 ON and OFF Cells 461 Linearizing ON and OFF Cells 463 The Function of the ON/OFF Distinction 466 Clynes Theory of Physiological Rein Control 466 APPENDIX F A Note on Spatial Sampling and Nyquist s Theorem 467 Nyquist s Theorem and Aliasing 467 Spatial Sampling of the Stimulus and Its Effect on Grating Detection Threshold 470 Spatial Sampling of the Stimulus and Its Effect on Spatial-Frequency Discrimination Threshold 476 Aliasing in Human Vision Caused by Undersampling of the Retinal Image by Retinal Photoreceptors 477 APPENDIX G The Measurement of Light 483 Photopic and Scotopic Vision 483 Photometric Units 484 The Measurement of Radiant Power 486 The Measurement of Color 487 APPENDIX H Linear and Logarithmic Scales: The Decibel 489 APPENDIX I Elements of Vector Calculus 491 Scalar and Vector Functions 491

12 Contents xvii Vector Fields 492 Div, Curl, and Grad 492 Div and curl 492 Grad 494 The Retinal Image Flow Field 494 Evidence That the Human Visual System Contains Filters for Rough Physiological Equivalents of Div V, Curl V, and Grad V 495 Expanding Retinal Flow Patterns and Div V Detectors 495 APPENDIX J Hypotheses, Experiments, Serendipity, Journals, and Grants 499 What Is It Like to Be a Researcher? 499 What Is Science? 501 The Role of Scientific Hypothesis 502 Where Do Hypotheses Come From? 503 Where Do Good Hypotheses Come From? 504 Fishing Expeditions and the Role of Luck 504 Can a Researcher Be Disadvantaged by Having an Encyclopedic and Up-to-date Knowledge of His or Her Research Area? 505 Journal Articles Give a Misleading Impression of How Scientists Operate 505 Grants 506 References 509 Illustration Credits 561 Index 563