Holistic and Analytic Representations' of Ignored and Attended Objects Thesis presented by Volker Thoma Department of Psychology Goldsmiths University of London November 2002 In Partial Fulfillment for the Degree of Doctor of Philosophy Acknowledgement I am indebted to Jules Davidoff who closely supervised my thesis and never let me get distracted. His direction, patience, and impatience were invaluable for this research project and the learning process associated with it. I am also grateful to John Hummel for welcoming me in his lab and introducing me to his model of object recognition. His enthusiasm for research was and is contagious. I further thank the cognitive research group at Goldsmiths' for their comments and even more so for their encouragement, in particular Alan Richardson-Klavehn, Linda Pring, Tim Valentine, and Steve Darling. Research needs infrastructure, and I was lucky to find the technical support I had at Goldsmiths', in particular provided by Maurice Douglas, Liz Elliott, Ian Hannent, Rob Davis, and Richard Billingham. And of course, I thank my participants for their time . .. Finally, I thank my friends Dani, Ulrich, Jonathan and Jane. Without them, I would have been lost. 2 Abstract Attended images prime both themselves and their left-right reflections, whereas ignored images prime themselves but not their reflections (Stankiewicz, Hummel, & Cooper, 1998). These and other effects are predicted by the hybrid theory of object recognition (Hummel & Stankiewicz, 1996a) that the human visual system represents ignored images holistically (i.e., view-based), and attended images both holistically and analytically (i.e., part-based). In nine experiments using a naming task the predictions of the model were tested with split, plane-rotated and depth-rotated views of common objects. Consistent with the prediction of the hybrid theory, Experiments 1 and 3 demonstrated that split images primed their intact and split counterparts when they were attended but not when they were ignored, whereas intact images primed themselves whether they were attended or not. Experiment 2 demonstrated that a substantial component of the observed priming for attended split images was specifically visual. In Experiment 5, attended images primed themselves fnd their plane-rotated versions (90°) whereas ignored images only primed themselves but not their rotated versions. Experiment 6 tested whether rotated objects with a definite upright orientation prime themselves in the same view. Substantial priming was observed for attended and ignored objects when shown in their upright view. However, rotated objects with a definite upright orientation primed themselves only when attended but not when ignored. This result indicates that ignored images make contact with stored representations. Experiment 7 replicated the findings of Stankiewicz et al. for mirror images but with grey­ level rendered 3D images. Experiment 8 tested priming for these objects using orientations in which parts change from study to test view. As before, there was substantial priming in all but the ignored-rotated condition. However, there was a greater reduction in priming for attended rotated objects than for ignored rotated objects. This result indicates that the representations mediating recognition of attended images are specifically sensitive to part changes. In Experiment 9, objects were rotated in depth such that equivalent parts were visible in both views. As in Experiment 7, the priming effects of view and attention were additive. 3 These data provide strong evidence that one function of visual attention is to permit the generation of analytic (i.e., part-based) representations of object shape. At the same time these results show that object recognition is also mediated by additional holistic representations. 4 Contents 1. Chapter 1: Introduction ...................................................................................................... 11 1.1 The Basic Problem and Scope of the Thesis .................................................................. 11 1.2 Object Recognition in the Brain .................................................................................... 14 1.2.1 Visual Pathways ....................................................................................................... 14 1.2.2 Representation of Shape in VI and Beyond .................................... :........................ 15 1.2.3 Image Transformations in the Ventral Pathway ....................................................... 19 1.3 Properties of Object Recognition ................................................................................... 20 1.3.1 View Invariance and View Dependency .................................................................. 20 1.3.2 Object Invariance Across Variations in Shape ......................................................... 23 1.4 Object Recognition Theories ......................................................................................... 26 1.4.1 The Debate on Formats of Object Representations .................................................. 26 1.4.2 View-based Models .................................................................................................. 28 1.4.2.1 Introduction ..................................................................................................... 28 1.4.2.2 Multiple Views Account (Tarr, 1995; Tarr & Pinker, 1989) ........................... 29 1.4.2.3 Alignment and Linear Combination of Views (Ullman, 1989, 1998) ............. 32 1.4.2.4 Metric Templates (Lades et aI., 1993) ............................................................. 32 1.4.2.5 Non-Linear View Interpolation (Poggio & Edelman, 1990) ........................... 33 1.4.2.6 Evidence in Support of View-based Models ................................................... 35 1.4.3 Part-Based Theories ................................................................................................. 37 1.4.3.1 Introduction ..................................................................................................... 37 1.4.3.2 Computational Theory of Object Recognition (Marr, 1982) ........................... 37 1.4.3.3 Geon Structural Description Theory (Biederman, 1987) ................................ 39 1.4.3.4 Evidence for Part-Based Models ..................................................................... 45 1.4.4 Evaluation of View-Based and Part-Based Models ................................................ .49 2. Chapter 2: Hybrid Accounts of Object Recognition .......................................................... 56 2.1 Introduction .................................................................................................................... 56 2.2 Accounts Stressing the Role of Process ......................................................................... 56 2.2.1 Mental Rotation ........................................................................................................ 56 2.2.1.1 Dual Route Account (Jolicoeur, 1990) ............................................................ 56 2.2.1.2 Double Checking (Corballis, 1988) ................................................................. 57 2.2.2 Holistic and Analytic Processing ............................................................................. 58 2.2.3 Process Determined by Task-Demands ................................. : .................................. 59 2.3 Accounts Stressing Multiple Representations ............................................................... 60 2.4 The Hybrid Model of Object Recognition (Hummel, 2001) ......................................... 64 2.4.1 Rationale for the Model.. .......................................................................................... 64 5 2.4.2 The Hybrid Model .................................................................................................... 66 2.4.3 Evidence for Hybrid Representations in the Brain ................................................... 74 2.4.4 Visual Attention ....................................................................................................... 76 3. Chapter 3: Experiments on Priming for Attended and Ignored Images ............................. 81 3.1 Rationale for the Use of the Priming Paradigm ............................................................. 81 3.2 Experiments 1-3: Priming for Intact and Split Objects .................................................. 82 3.2.1 Introduction .............................................................................................................. 82 3.2.2 Experiment 1: Priming for Split and Intact Images .................................................. 85 3.2.2.1 Method ............................................................................................................. 85 3.2.2.2 Results ............................................................................................................. 87 3.2.2.3 Discussion ....................................................................................................... 89 3.2.3 Experiment 2: Visual Priming for Split Images ....................................................... 90 3.2.3.1 Introduction ..................................................................................................... 90 3.2.3.2 Method ............................................................................................................. 91 3.2.3.3 Results ............................................................................................................