STEREOSCOPIC SURFACE INTERPOLATION FROM ILLUSORY CONTOURS BRITTNEY HARTLE A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS GRADUATE PROGRAM IN PSYCHOLOGY YORK UNIVERSITY TORONTO, ONTARIO September 2016 © Brittney Hartle, 2016 Abstract Stereoscopic Kanizsa figures are an example of stereoscopic interpolation of an illusory surface. In such stimuli, luminance-defined disparity signals exist only along the edges of inducing elements, but observers reliably perceive a coherent surface that extends across the central region in depth. The aim of this series of experiments was to understand the nature of the disparity signal that underlies the perception of illusory stereoscopic surfaces. I systematically assessed the accuracy and precision of suprathreshold depth percepts using a collection of Kanizsa figures with a wide range of 2D and 3D properties. For comparison, I assessed similar perceptually equated figures with luminance-defined surfaces, with and without inducing elements. A cue combination analysis revealed that observers rely on ordinal depth cues in conjunction with stereopsis when making depth judgements. Thus, 2D properties (e.g. occlusion features and luminance relationships) contribute rich information about 3D surface structure by influencing perceived depth from binocular disparity. ii Table of Contents Abstract ......................................................................................................................................................... ii Table of Contents ......................................................................................................................................... iii Chapter 1: Introduction .................................................................................................................................. 1 Section 1.1: Illusory Contours .................................................................................................................... 1 Section 1.2: Occlusion Geometry ............................................................................................................... 3 Section 1.3: Lightness Illusion ................................................................................................................... 6 Section 1.4: Stereoscopic Kanizsa Figures ................................................................................................. 7 Section 1.4.1: Depth from Inducer Disparity Alone............................................................................. 10 Section 1.4.2: Depth from Illusory Contour Disparity ......................................................................... 11 Section 1.5: Current Study ....................................................................................................................... 12 Section 1.6: General Methods .................................................................................................................. 14 Section 1.6.1: Observers ....................................................................................................................... 14 Section 1.6.2: Stimuli ........................................................................................................................... 14 Section 1.6.3: Apparatus ...................................................................................................................... 16 Chapter 2: Lightness ..................................................................................................................................... 16 Section 2.1: Perceived Lightness of Illusory Boundaries ......................................................................... 16 Section 2.1.1: Rationale ....................................................................................................................... 18 Section 2.2: Methods for Experiment 2.1 ................................................................................................. 19 Section 2.3: Results and Discussion ......................................................................................................... 21 Chapter 3: Inducer Diplopia ......................................................................................................................... 23 Section 3.1: Introduction .......................................................................................................................... 23 Section 3.1.1: Rationale ....................................................................................................................... 23 Section 3.2: Methods for Experiment 3.1 ................................................................................................. 24 Section 3.3: Results and Discussion ......................................................................................................... 25 Chapter 4: Accuracy ..................................................................................................................................... 27 Section 4.1: Introduction .......................................................................................................................... 27 Section 4.1.1: Depth Magnitude Rationale .......................................................................................... 28 Section 4.2: Methods for Experiment 4.1 ................................................................................................. 29 Section 4.3: Results and Discussion ......................................................................................................... 32 Section 4.3.1: Disparity Probe Rationale ............................................................................................. 36 iii Section 4.4: Methods for Experiment 4.2 ................................................................................................. 36 Section 4.5: Results and Discussion ......................................................................................................... 39 Section 4.5.1: Fused Standard .............................................................................................................. 40 Section 4.5.2: Diplopia Standard .......................................................................................................... 42 Section 4.6: Discussion ............................................................................................................................ 44 Section 4.6.1: Do Illusory Boundaries Interpolate to a Shallower Surface at the Diplopia Point? ...... 44 Section 4.6.2: Differences in the Depth Magnitude Task .................................................................... 45 Section 4.6.3: Reduction of the Perceived Peak ................................................................................... 46 Chapter 5: Precision ..................................................................................................................................... 47 Section 5.1: Introduction .......................................................................................................................... 47 Section 5.1.1: Rationale ....................................................................................................................... 49 Section 5.2: Methods for Experiment 5.1 ................................................................................................. 50 Section 5.3: Results and Discussion ......................................................................................................... 51 Section 5.3.1: Fused Standard .............................................................................................................. 53 Section 5.3.2: Diplopia Standard .......................................................................................................... 54 Section 5.4: Cue Combination .................................................................................................................. 57 Section 5.4.1: Introduction ................................................................................................................... 57 Section 5.4.2: Linear Cue Combination ............................................................................................... 58 Section 5.4.3: Our Model ..................................................................................................................... 59 Section 5.4.4: Alternative Cue Combination Models ........................................................................... 63 Chapter 6: Discussion ................................................................................................................................... 65 Section 6.1: Summary .............................................................................................................................. 65 Section 6.2: Contribution of 2D and 3D Illusory Boundaries .................................................................. 67 Section 6.3: Interpolation of Illusory Boundaries .................................................................................... 68 Section 6.3.1: Perceived Shape of Illusory Boundaries ....................................................................... 68 Section 6.3.2: Occlusion Features and Disparity ................................................................................. 70 Section 6.3.3: Disparity Ownership ....................................................................................................