Dr. Thorsten Hansen

Senior Scientist


Department of General and Experimental Psychology
Justus Liebig University Giessen
Otto-Behaghel-Str. 10 F1
35394 Giessen
Germany

Campus: Phil I, F1, Room 315
Email: Thorsten.Hansen@psychol.uni-giessen.de
Phone: +49 641 9926107
Fax: +49 641 9926119
   Thorsten Hansen



I am interested in the principles underlying visual information processing and representation in men and machines, in particular color, luminance, and form.



Horizontal line

[Publications]  [Talks]  [Teaching]  [Research]  [Awards]  



CV

2002   Ph.D. in Computer Science (Dr. rer. nat.), University of Ulm, Germany
1997   Diploma in Computer Science, “mit Auszeichnung”, Technical University of Braunschweig, Germany


Gray line


Publications

Find my publications indexed byPubMed

Journal Articles (25)

Witzel, C., Valkova, H., Hansen, T. & Gegenfurtner, K. R. (2011). Object knowledge modulates colour appearance. iPerception, 2, 13–49.
Olkkonen, M., Witzel, C., Hansen, T., & Gegenfurtner, K. R. (2010). Categorical color constancy for real surfaces. Journal of Vision, 10(9):16, 1–22.
Hamburger, K., & Hansen, T. (2010). Analysis of individual variations in the classical horizontal-vertical illusion. Attention, Perception, & Psychophysics, 72(4), 1045–1052.
Olkkonen, M., Hansen, T., & Gegenfurtner, K. R. (2009). Categorical color constancy for simulated surfaces. Journal of Vision, 9(12):6, 1–18.
Giesel, M., Hansen, T., & Gegenfurtner, K. R. (2009). The discrimination of chromatic textures. Journal of Vision, 9(9):11, 1–28.
Hansen, T., Pracejus, L., & Gegenfurtner, K. R. (2009). Color perception in the intermediate periphery of the visual field. Journal of Vision, 9(4):26, 1–12.
Hansen, T., & Gegenfurtner, K. R. (2009). Independence of color and luminance edges in natural scenes. Visual Neuroscience, 26, 35–49.
Hansen, T., & Neumann, H. (2008). A recurrent model of contour integration in primary visual cortex. Journal of Vision, 8(8):8, 1–25. [www.journalofvision.org]
Supplementary material New 2011-02-21: Full model implemenation as supplementary material available from this website The zip archive used to be hosted by Journal of Vision, but Silvia Elena Corchs send me an email that she could not download it—neither could I on 2011-02-21—so I decided to provide the Matlab code of the model implementation as well on my web site for download:./downloads/contourmodel.zip [1.3 M]. Besides the model implementation, the code includes the file makefig.m that generates all figures of the article resulting from model simulations (i.e., all figures but Figs. 1 and 17). Please refer to the source with some phrase as the following, when using (parts) of the code:
The model was based on the implementation of a recurrent neural model for contour integration in primary visual cortex (Hansen & Neumann, 2008).
Prerequisites: Matlab with the Image Processing Toolbox.

Quick start guide (from 2008-04-08)

  • Download the zip file contourmodel.zip [1.3 M] and extract
  • Start Matlab (Image Processing Toolbox required)
  • Add directory contourmodel including all subdirectories to Matlab's search path
  • In Matlab: use cd to change to directory "contourmodel"
  • Run example to simulate the response to the noisy square
  • Run makefig(2) to generate the eps-file for Fig. 2 of the article
  • Run makefig('all') to generate eps-files for all figures

    • Olkkonen, M., Hansen, T., & Gegenfurtner, K. R. (2008). Colour appearance of familiar objects: effects of object shape, texture and illumination changes. Journal of Vision, 8(5):13, 1–16. [www.journalofvision.org]
    Hansen, T., Giesel, M., & Gegenfurtner, K. R. (2008). Chromatic discrimination of natural objects. Journal of Vision, 8(1):2, 1–19. [www.journalofvision.org/8/1/2]
    Devinck, F., Hansen, T., & Gegenfurtner, K. R. (2007). Temporal properties of the chromatic and achromatic Craik-O'Brien-Cornsweet effect. Vision Research, 47(27), 3385–3393.
    top 25 Hottest Articles logo

     Vision Research, October–December 2007
    Hamburger, K., Hansen, T., & Gegenfurtner, K. R. (2007). Geometric-optical illusions at isoluminance. Vision Research, 47(26), 3276–3285.
    Hansen, T., Walter, S., & Gegenfurtner, K. R. (2007). Effects of spatial and temporal context on color categories and color constancy. Journal of Vision, 7(4):2, 1–15. [www.journalofvision.org]
    Cover Nature Neuroscience 2006 9(11)
    Hansen, T., Olkkonen, M., Walter, S. & Gegenfurtner, K. R. (2006). Memory modulates color appearance. Nature Neuroscience, 9(11), 1367–1368. [Nature Neuroscience] [Supplementary Methods]

    Echo in the media

    Hansen, T. & Gegenfurtner, K. R. (2006). Kortikale Mechanismen des Farbensehens. Neuroforum, 2, 197–203. [Neuroforum]
    Hansen, T. & Gegenfurtner, K. R. (2006). Color scaling of discs and natural objects at different luminance levels. Visual Neuroscience, 23 (3–4), 603–610. [journals.cambridge.org]
    Hansen, T., & Gegenfurtner, K. R. (2006). Higher level chromatic mechanisms for image segmentation. Journal of Vision, 6(3), 239–259. [www.journalofvision.org]
    Sharpe, L. T., De Luca, E., Hansen, T., Jägle, H., & Gegenfurtner, K. R. (2006). Advantages and disadvantages of human dichromacy. Journal of Vision, 6(3), 213–223. [www.journalofvision.org]
    Hansen, T., & Gegenfurtner, K. R. (2005). Classification images for chromatic signal detection. Journal of the Optical Society of America (A), Feature issue on Visual Coding in memory of Russell L. De Valois, 22(10), 2018–2089.
    Keil, M., Cristóbal, G., Hansen, T., & Neumann, H. (2005). Recovering Real-World Images from Single-Scale Boundaries with a Novel Filling-in Architecture. Neural Networks, 18(10), 1319–1331.
    Hansen, T., & Neumann, H. (2004). A simple cell model with dominating opponent inhibition for robust image processing. Neural Networks, 17(5–6), 647–662.
    Hansen, T., & Neumann, H. (2004). Neural mechanisms for the robust detection of junctions. Neural Computation, 16(5), 1013–1037.
    Neumann, H., Pessoa, L., & Hansen, T. (2001). Visual filling-in for computing perceptual surface properties. Biological Cybernetics 85(5), 355–369. © Springer. The original publication is available at www.springerlink.com
    Hansen, T., Baratoff, G., & Neumann, H. (2000). A simple cell model with dominating opponent inhibition for robust contrast detection. Kognitionswissenschaft, 9(2), 93–100. ©Springer. The original publication is available at www.springerlink.com
    Neumann, H., Pessoa, L., Hansen, T. (1999). Interaction of ON and OFF pathways for visual contrast measurement. Biological Cybernetics 81(5–6), 515–532. © Springer. The original publication is available at www.springerlink.com

    Book Chapters (9)

    Olkkonen, M., Hansen, T., & Gegenfurtner, K. R. (to appear). High level perceptual influences on color appearance. In S. Allred, & G. Hatfield (Eds.), Visual Experience. Oxford, MA: Oxford University Press.
    Hansen, T. (2009). Color naming. In E. Bruce Goldstein (Ed.), SAGE Encyclopedia of Perception. Invited essay.
    Hansen, T. & Gegenfurtner, K. R. (2007). Color processing. In U. Windhorst, M. Binder, & H. Hirokawa (Eds.), Springer Encyclopedia of Neuroscience. Heidelberg: Springer-Verlag. © Springer-Verlag.
    Hansen, T., & Gegenfurtner, K. R. (2007). Higher order color mechanisms for image segmentation. In F. Mele, G. Ramella, S. Santillo, & F. Ventriglia (Eds.), Brain, Vision and Artificial Intelligence 2007 . LNCS/LNAI. Heidelberg: Springer-Verlag. © Springer-Verlag.
    Hansen, T., & Gegenfurtner, K. R. (2007). Farbwahrnehmung. In J. Steinbrenner & S. Glasauer (Eds.), Farben – Betrachtungen aus Philosophie und Naturwissenschaften (pp. 277–291). Frankfurt am Main: Suhrkamp.
    Gegenfurtner, K. R. & Hansen, T. (2006). Farbwahrnehmung – Color Vision. In J. Funke & P. A. Frensch, (Eds.), Handbuch der Allgemeinen Psychologie – Kognition. Göttingen: Hogrefe.
    Hansen, T., & Neumann, H. (2002). A biologically motivated scheme for the robust detection of junctions. In H. H. Bülthoff, S.-W. Lee, T. A. Poggio, & C. Wallraven (Eds.), Biologically Motivated Computer Vision (BMCV 2002) (pp. 16–26). LNCS 2525. Berlin: Springer-Verlag. © Springer-Verlag.
    Hansen, T., Sepp, W., & Neumann, H. (2001). Recurrent long-range interactions in early vision. In S. Wermter, J. Austin, & D. Willshaw (Eds.), Emergent Neural Computational Architectures Based on Neuroscience (pp. 139–153). LNCS/LNAI 2036. Heidelberg: Springer-Verlag. © Springer-Verlag.
    Hansen, T., & Neumann, H. (2001). Neural mechanisms for representing surface and contour features. In S. Wermter, J. Austin, & D. Willshaw (Eds.), Emergent Neural Computational Architectures Based on Neuroscience (pp. 127–138). LNCS/LNAI 2036. Heidelberg: Springer-Verlag. © Springer-Verlag.

    Selected Conference Papers

    Hansen, T., & Neumann, H. (2004). Robust contour extraction and junction detection by a neural model utilizing recurrent long-range interactions. In U. J. Ilg, H. H. Bülthoff, & H. A. Mallot (Eds.), Dynamic Perception, (pp. 177–182). Berlin: Akademische Verlagsgesellschaft Aka.


    Talks

    Invited talks (8)

    Hansen, T. (2011). The contribution of color to detecting edges in natural scenes. Computational Color Imaging Workshop, CCIW 2011, University of Milano-Bicocca, Italy. Apr. 20, 2011.
    Hansen, T. (2010). Multiple mechanisms in higher order color processing. Institute for Basic Psychological Research, Faculty of Psychology, University of Vienna. Jan. 19, 2010.
    Hansen, T. (2008). Color perception. Institute for Basic Psychological Research, Faculty of Psychology, University of Munster, Germany. Nov. 2008.
    Hansen, T. (2008). Chromatic discrimination. Visual Perception Lab, Department of Psychology, Christian-Albrechts-University Kiel, Germany. Nov. 2008.
    Hansen, T. (2007). Higher order color processing. Honda Research Institute Europe, Offenbach/Main, Germany. Oct. 16, 2007.
    Hansen, T. (2007). Wie unser Gedächtnis die Farbwahrnehmung beeinflußt. Farbinfo 2007, Stuttgart, Germany. Sep. 28, 2007.
    Hansen, T. (2007). Chromatic discrimination of synthetic and natural textures. British Colour Group Vision meeting, Institute of Ophthalmology, London, UK. Jan. 10, 2007.
    Hansen, T. (2004). A neural model of early visual processing utilizing recurrent long-range interactions. TeaP 2004, Giessen, Germany. Apr. 6, 2004.

    Conference talks

    coming sometimes...





    Gray line


    Research

    Color Vision

    We combine psychophysical methods, computational modeling and natural scene statistics to investigate the principles of early and higher order mechanisms of color processing.

    		 Color cube

    The number and nature of higher order color mechanisms

    Color vision begins in the retina with three different type of photoreceptors. These responses are combined already in the retina to form three different channels. These early retinal stages are well understood. The further processing of the color signal in the cortex is less well understood. Physiologists have measured what color a neuron prefers, i.e., to which it responds best. In the primary visual cortex, the first stage of cortical processing, the color preferences span the full color circle. In psychophysical studies we complement these physiologicial findings and show that the detection of color is mediated by many mechanisms. However, other researchers have found only a few mechanims. How does this discrepancy occur? In our recent work we have shown that those who found few mechanisms have used an suboptimal set of stimuli to probe the full range of mechanisms.

    		 Eye

    Neural Models in Early Vision

    The research covers a broad range of processing mechanisms in early vision, motivated by empirical findings and computational considerations:

    • contrast and edge detection
    • contour detection and grouping
    • corner and junction detection
    • surface perception

    These topics have been examined as part of my Ph. D. thesis supervised by Heiko Neumann.

    		Eye


    Gray line


    Awards and Fellowships

    GK logo GI logo

    The paper A Neural Model of Dominating Opponent Inhibition in Visual On and Off Pathways for Robust Contour Extraction has been awarded the `KI/Kognitionspreis' for the best contribution of a young scientist in the field `Kognitionswissenschaftliche KI', assigned by the `Gesellschaft für Kognitionswissenschaft' and the `Fachbereich 1 der Gesellschaft für Informatik' at the `Fachtagung der Gesellschaft für Kognitionswissenschaft', KogWis, 1999.

    CNS logo BU seal

    Postdoctoral fellow travel fellowship. 7th International conference on cognitive and neural systems ICCNS 2003, Boston, MA.

    Graduate student travel fellowship. 6th International conference on cognitive and neural systems ICCNS 2002, Boston, MA.



    Reviewer

    Foundations

    Journals

    Ph. D. Theses



    Symposia

    Session Chair "Visuelle Wahrnehmung", TeaP 2007, Trier, Germany.

    Session Chair of the Symposium "Color Vision", TeaP 2006. Symposium organized together with Karl R. Gegenfurtner.

    Monday, 27. March 2006
    09:30–10:30 Symposium 5a und 5b: Color Vision
    Thorsten Hansen, Karl R. Gegenfurtner
    09:30Introduction
    09:45Lindsay T. Sharpe: Advantages and disadvantages of human colour- blindness
    10:00 Rainer Hertel, Thomas Wachtler: Color categories of dichromats
    10:15 Hans Irtel: On the appearance of small and very large fields of color
    10:30–11:00coffee break
    11:00Annette Werner: Moving Colors
    11:15Jürgen Golz: Chromatic statistics of natural scenes and their role for colour constancy
    11:30Laurence T. Maloney, Huseyin Boyaci, Katja Doerschner, Jacqueline L. Snyder: Surface color perception in three-dimensional scenes
    11:45Thorsten Hansen, Sebastian Walter, Karl G. Gegenfurtner: Memory color effects of natural objects on color constancy


    Presentations, demos and exhibitions



    Teaching

    Stud.IP

    Lectures

    SS 2004 Vorlesung Sinnesphysiologie und Wahrnehmung:
    Two lectures on color vision (in German)
      Farbwahrnehmung I
      Farbwahrnehmung II

    Seminars

    WS 2009/2010
    Seminar (Visuelle) Wahrnehmung

    SS 2005 - SS 2008
    Blockkurs Psychophysische Methoden und Matlab Programmierung

    SS 2006
    Computer Exercises Matlab, Psychtoolbox, Color image processing, Motion at the European Summer School "Visual Neuroscience &mdash from Spikes to Awareness", Sep. 6–17, 2006. Organized by Frank Bremmer, Jochen Braun and Karl R. Gegenfurtner at Rauischolzhausen Castle, Germany.

    SS 2005 Blockkurs Psychophysik

    WS 2004/2005
    Seminar Visuelle Wahrnehmung
    Seminar Farbwahrnehmung

    SS 2004 Seminar Farbwahrnehmung
    SS 2004 Blockkurs Psychophysische Methoden im Graduiertenkolleg Neuronale Repräsentation und Handlungssteuerung NeuroAct
    SS 2004: Computer Exercise Color Image Processing at the European Summer School "Visual Neuroscience-from Spikes to Awareness", Sep. 6–17, 2004. Organized by Frank Bremmer, Jochen Braun and Karl R. Gegenfurtner at Rauischolzhausen Castle, Germany.

    SS 2003 Seminar: Methoden der Psychophysik

    Theses Supervision

    Ph. D. Theses (together with Prof. Dr. Karl R. Gegenfurtner)

    Martin Giesel (2009). Chromatic discrimination of complex stimuli.

    Maria Olkkonen (2009). Investigating the mechanisms of real-world color constancy.

    Kai Hamburger (2007). Visual illusions: Perception of luminance, color, and motion in humans.

    Lars Pracejus (2007). Defective color vision (Wahrnehmungsdefizite bei zentralen neurologischen Erkrankungen &ndash Farbwahrnehmung auf retinaler und zerebraler Ebene).

    Sebastian Walter. Color constancy, color categorization, aesthetic color-form preferences, lens brunescense.

    Christoph Witzel. Color, categories and memory.

    Diploma Theses

    Florian Bayer (2009). A biologically-inspired neural network for motion detection &ndash modelling and psychophysics. Abteilung Allgemeine Psychologie der Justus-Liebig-Universität Gießen.

    Stefanie Weis (2009). Einfluss von Farbe auf die Steuerung von Aufmerksamkeit und Blickbewegungen bei abstrakten Bildern und Werbeplakaten. Abteilung Allgemeine Psychologie der Justus-Liebig-Universität Gießen.

    Lukas Kaim (2006). Interaktive Simulation einer parvozellulären retinalen Ganglienzelle. Fachbereich Informatik der Fachhochschule Gießen-Friedberg und Abteilung Allgemeine Psychologie der Justus-Liebig-Universität Gießen.

    Bachelor Theses

    Arkadius Gotz (2010). Einfluss von lokalem Kontrast und Beleuchtungsfarbe auf die Farbkonstanz. Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen.

    David Weiß (2010). Einfluss von 2D und 3D Hinweisreizen und verschiedenfarbigen Beleuchtungen auf die Farbkonstanz. Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen.

    Undergraduate Projects (Semesterarbeiten)

    Laura Fietze (2007): Frauen können Rottöne besser unterscheiden? — Untersuchung geschlechterspezifischer Unterschiede in der chromatischen Diskrimination

    Martin Krebber (2007): Können Grüntöne besser unterschieden werden als Rottöne? — Untersuchung farbtonspezifischer Unterschiede in der chromatischen Diskrimination

    Franziska Stephanie Urban (2006): Raumzeitliche Klassifikationsbilder zur Untersuchung chromatischer Signalentdeckung

    Mario Dirks (2005): Einfluß der Gedächnisfarbe auf die Farbwahrnehmung. Received the second poster award at the annual faculty students' poster presentation.

    Andrea Fuchs (2005): Farbkategorisierung von natürlichen Objekten.

    Anke Haberkamp (2005): Geometrisch-optische Täuschungen unter Isoluminanz.

    Judith Kowalsky (2005): Die Untersuchung möglicher Korrespondenzen zwischen Grundfarben und Grundformen.

    Filipp Schmidt (2005): Farbdiskriminierung bei natürlichen Objekten.

    Daniel Drescher (2004): Objektbezogenen Farbdiskriminierung.



    Gray line

    Links

    Valid HTML 4.01 Transitional