Saliency from the decision perspective: Inferring the processing architecture of pre-attentive vision with mental chronometry Michael Zehetleitner M¨unchen 2007 Saliency from the decision perspective: Inferring the processing architecture of pre-attentive vision with mental chronometry Michael Zehetleitner Dissertation an der Fakult¨atf¨urPsychologie und P¨adagogik der Ludwig–Maximilians–Universit¨at M¨unchen vorgelegt von Michael Zehetleitner aus Kempten im Allg¨au M¨unchen, den 2. November 2007 Erstgutachter: Prof. Dr. Hermann J. M¨uller Zweitgutachter: Prof. Dr. Joseph Krummenacher Tag der m¨undlichen Pr¨ufung: 20. Dezember 2007 To Norbert Bischof, without whom not. vi ACKNOWLEDGMENTS Norbert Bischof, in his lectures and in personal communication, ignited my cu- riosity for animal and human psychology and provided me with a psychological and philosophical framework as footholds for investigating such issues. Additionally his cybernetic, supported by Felix Tretter’s system theoretical approach influenced my thinking intensly. In particular, I would like to thank my mentor and supervisor of this thesis, Her- mann M¨uller,for focussing my mind to the art of psychological experimentation and for providing me with the freedom to pursue very interesting questions answerable with mental chronometry. I thank Joseph Krummenacher for introducing me to the redundant-signals paradigm and being my contact person for experimental, writing, or statistical questions from the beginning of my studies of neuro-cognitive psychol- ogy. Being part of a large unit of colleagues also was of great help for developing and discussing experiments, as well as for gaining new insights. Specifically, I would like to mention Thomas Geyer, Thomas T¨ollner, Zhuanghua Shi, and Dragan Rangelov for valuable discussions and input for this thesis. I had the chance to be supported by Henning Bumann, Yvonne Schiller, Michael Hegenloh, and Frieder Wormser, who carried out the experiments and collected the data. All work related support would be nothing without my family: my wife Ilona, our sons Franz and Peter, as well as our parents. Finally, I thank the Deutsche Forschungsge- meinschaft for funding the CoTeSys Excellence Cluster, which financed my research. vii TABLE OF CONTENTS Page ABSTRACT ................................... ix 1 INTRODUCTION .............................. 1 1.1 Salience map models .......................... 1 1.2 Modulation of salience ......................... 3 1.2.1 The redundant-signals effect .................. 3 1.2.2 Dimension switch costs and cueing benefits .......... 4 1.3 Alternative processing architectures .................. 6 1.4 Scope of the present study ....................... 8 1.5 Summary of findings .......................... 9 1.5.1 Chapter 2 ............................ 9 1.5.2 Chapter 3 ............................ 9 1.5.3 Chapter 4 ............................ 11 1.5.4 Chapter 5 ............................ 13 1.6 Conclusion and outlook ......................... 14 2 WHAT THE REDUNDANT-SIGNALS PARADIGM CAN REVEAL .. 17 2.1 The redundant-signals paradigm .................... 18 2.2 The question of architecture: parallel, co−active, or serial? ..... 22 2.3 Is integration spatially selective? .................... 27 2.4 Is integration feature−based or dimension−based? .......... 32 2.5 Weighting or priming? ......................... 34 2.6 Implementation of saliency maps and dimensional weighting in the brain 38 2.7 Conclusion ................................ 43 3 CO-ACTIVATION VS. SERIAL AND PARALLEL MODELS ...... 45 3.1 Experiment 1 .............................. 53 3.1.1 Method ............................. 54 3.1.2 Data Analysis .......................... 57 3.1.3 Results .............................. 60 3.1.4 Discussion ............................ 63 3.2 Experiment 2 .............................. 64 3.2.1 Method ............................. 64 3.2.2 Results and Discussion ..................... 65 3.3 Experiment 3 .............................. 66 3.3.1 Method ............................. 72 3.3.2 Results .............................. 74 viii Page 3.3.3 Discussion ............................ 77 3.4 General Discussion ........................... 78 4 INTENTION AND TRIAL HISTORY IN LOCALIZATION ....... 89 4.1 Experiment 1 .............................. 95 4.1.1 Method ............................. 96 4.1.2 Results .............................. 99 4.1.3 Discussion ............................ 102 4.2 Experiment 2 .............................. 105 4.2.1 Method ............................. 106 4.2.2 Design and Procedure ..................... 106 4.2.3 Results .............................. 107 4.2.4 Discussion ............................ 107 4.3 General Discussion ........................... 110 4.3.1 Summary of findings ...................... 110 4.3.2 Relations to post-selective accounts .............. 112 4.3.3 Relation to further studies ................... 114 4.3.4 Summary and conclusion .................... 118 5 DECISION PERSPECTIVE ON SALIENCY ............... 121 5.1 The RSE ................................. 133 5.1.1 Manipulation of feature contrast ................ 133 5.1.2 Manipulation of response bias ................. 134 5.1.3 The effect of spatial attention ................. 136 5.2 Benefits from Dimensional Cues .................... 136 5.3 Dimension Switch Costs ........................ 137 5.4 Experiment 1 .............................. 138 5.4.1 Method ............................. 139 5.4.2 Results .............................. 141 5.4.3 Discussion ............................ 148 5.5 Experiment 2 .............................. 150 5.5.1 Method ............................. 150 5.5.2 Results .............................. 152 5.5.3 Discussion ............................ 153 5.6 General Discussion ........................... 153 5.6.1 Relation to previous studies .................. 156 5.6.2 Theoretical Implications .................... 164 5.7 Conclusion ................................ 165 REFERENCES .................................. 167 VITA ....................................... 178 ix ABSTRACT There are several cognitive and neuro-scientific models of early, pre-attentive vi- sual processing, with saliency map models being the particular dominant ones. Al- though they are very specific about how feature contrast and salience are being com- puted (including stimulus- and observer-driven influences), there usually is a theoreti- cal gap between models dealing with visual analysis (such as the dimension weighting account, M¨uller,Heller, & Ziegler, 1995; Found & M¨uller,1996) and models de- scribing decision and response selection processes (e.g. the Ratcliff Diffusion Model, Ratcliff, 1978). Consequently, I propose that investigating saliency from a decision perspective that is by applying mathematical theories of decisions to several tasks that can be performed supposedly based on a salience map (e.g. detection, localiza- tion, attentional selection), explanatory power is increased and new hypothesis can be generated. Further, several issues of visual pre-attentive processing are currently still under de- bate. Specifically, the exact nature of the pre-attentive architecture is disputed with regard to trial sequence, intention, and redundancy effects. The present study targets at shedding new light on the question of pre-attentive processing architecture (serial, parallel independent or interactive, co-active), top-down penetrability of pre-attentive vision, and pre-attentive vs. post-selective locus of dimensional inter-trial effects. In summary, the findings presented in this thesis support the predictions of the di- mension weighting account that is that dimension-specific feature contrast signals are computed in parallel and are dimensionally weighted before being pooled on the mas- ter saliency map. They further support the view that dimensional weighting operates at a pre-attentive processing stage and is modulated by trial history (i.e. bottom- up) as well as by intention (i.e. top-down). Further, the present results suggests that different tasks such as detection, localization, and compound tasks act upon x the same (salience map) representation. Finally, examining salience from a decision perspective provides an explanatory framework of how the observed performance dif- ference induced by the redundant-signals effect, dimension switch costs, or benefits from dimensional cues depend on the duration of the underlaying decision process. 1 1. INTRODUCTION All animals are limited in their possibilities to interact with the environment. Hu- mans and other primates have two hands to grasp or point with, one head to turn, one pair of eyes with one fovea each to look at with, while the amount of possible locations and objects in the environment to use these effectors on seems unlimited in comparison. Additionally the processing system to control behavior, the brain, is limited in its capacity to deal with the environmental complexity, as well (Tsotsos, 1990; Rensink, O’Regan, & Clark, 1997). Given these limitations of animals with regard to the complexity of the environment it was necessary to adaptively solve a problem of selection. For an adaptive control of selection there had to be a trade-off between responding to the affordances of the environment and choosing actions based on the internal state of the organism. The effect of internal states can operate on the sensory level, by enhancing certain sensory properties that are known to be more relevant over others, or on a semantic level, for which