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Dr Johannes M. Zanker
Diplom (Tübingen, Germany),
Ph.D. (Tübingen, Germany)
Professor of Neuroscience, HoD, Department of Psychology,
Royal Holloway University of London, Egham, Surrey TW20 0EX
Room W 214, Phone +44 (0)1784 443521, FAX +44 (0)1784 43434
email: j.zanker@rhul.ac.uk
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Johannes joined the Vision
Group (now BAB)
in the Department
of Psychology in March 2000. Trained as biologist with a special
emphasis on theoretical aspects (cybernetics), his interest is now
focused on visual information processing in humans,
in particular motion perception, and possible applications in artificial
systems. Previous appointments include:
In the Psychology Department
Johannes has served as Director of Graduate Diploma, Director of
Research, and Chair of the Departmental Ethics Committee, and in
2005 has been appointed as Head of Department. From 2003-2006 he
was Scientific Director of HolViz Ltd. - a spinout company of RHUL
to commercalise IP in visual processing. Have a look at his recently
published textbook ' Sensation,
Perception and Action- An Evolutionary Perspective '.
... a few details about research, publications,
current and previous
teaching
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summary of research interests:
Psychophysics and Computational Modelling
- Perception of primary
and secondary motion. Motion percepts are not only
elicited by displacements of contours which are defined by changes in average
luminance, but also by shifting contrast-defined or even motion-defined contours
('theta-motion', Zanker 1993). This has interesting consequences for models
of motion processing. Together with Nick
Burns (Adelaide, Australia) the interaction
between primary and secondary motion was studied, leading to characterstic
misperceptions of motion direction.
- Barbers Pole illusion.
The barberspole illusion (the diagonal stripes on
a rotating cylinder seem to move vertically although the actually move horizontally)
demonstrates how a particular shape of an aperture can change the perceived
direction of motion (Fisher & Zanker 2001). Together with Eric
Castet (Marseille, France) we investigated how the shape of a particular
aperture forces the visual system to adopt a particular solution when integrating
ambiguous motion signals from the central regions of the aperture and
disambiguated motion signals from the boundary regions.
- Motion illusions
perceived in static images. The role of
eye movements for perceiving motion in simple patterns such as used by Op
artists, is investigated in collaboration with Robin
Walker and Frouke Hermens.
Small involuntary saccades, which are frequently made by observers under a
wide range of conditions, lead to characteristically incoherent patterns of
motion signals for Op art paintings like Bridget Riley's 'Fall' while generating
coherent motion signals for control patterns, which then can be used to correct
for retinal image shifts. Supported by The
Leverhulme Trust.
- Understanding segmentation
and motion transparency, optic flow. In the psychophysical
laboratory and in real life scenes, one may come across surprising situations
in which two different directions of motion appear within the same patch of
the visual field. This creates specific problems for the elementary motion
detecting mechanism and can be interpreted in the context of motion-based
contour detection and as limiting case of motion-based segmentation (in collaboration
with Szonya Durant
and Andrew
Meso). The latest work in this area deals with the question of how attention
affects the number of simultaneously perceived directions (in collaboration
with Fatima
Felisberti). Supported by BBSRC
and EPSRC.
- Visual
ecology. Vision is an exemplary case
of how sensory and, more general, nervous systems are adapted to the specific
requirements which are imposed on an organism by its physical and social surroundings.
The specific adaptations of visual systems within their ecological niche
and the information content of natural scenes, somehow reflected by the perceptual
capabilities, are investigated in a collaboration with Jochen
Zeil (CVS, Canberra, Australia) and Szonya
Durant. In particular, we are interested in the strucutre of optical
flow in natural environments and motion signal patterns in animal communication
(Zanker 2007).
- Neuromorphic engineering. The application
of our knowledge about motion processing in biological visual systems, in
particular motion parallax as depth cue, is pursued in a Royal Holloway spin-out
company, HolViz Ltd., carrying out a proof-of-the-concept study for a novel
design of 3D X-Ray security scanners.
- Speed perception.
The perceived speed of moving patterns depends on a number of stimulus
parameters other than physical speed, such as contrast or size. Together with
Martin
Egelhaaf (Bielefeld, Germany) and Srini
Srinivasan (Canberra, Australia) it was investigated how velocity
can be encoded in correlation-type motion detectors independent of spatial
frequency, which recently was extended to broad-band stimuli with Andrew
Meso (Meso and Zanker 2009). Effects of uncorrelated noise on speed perception
are investigated in collaboration with Oliver
Braddick (Oxford/UCL, England). The influence of apertures on perceived
speed is investigated together with Josh Ryan (Canberra, Australia).
- Orientation maps in the human cortex. From
electrophysiological studies in primates it is apparent that in the retinotopic
map of the visual field on the early cortex is organized in small modules
called 'hypercolumns'. The preferred orientation of neurones in the primary
visual cortex are arranged in a characteristic 'pinwheel' structure around
centres with negligible orientation sensitivity. Can we trace these orientation
maps in humans with psychophysical techniques ? (with Valentino
Braitenberg, Tübingen, Germany).
- Perception of shape.
Gestalt psychology collected manifold evidence that the human visual
system shows preferences for 'good shapes'. Can this notion be verified in
a quantitative sense? In a collaboration with Tanja
Quenzer (Tübingen, Germany) the discrimination of circles/squares from
ovals/rectangles with different sidelengths was analysed under a variety of
viewing conditions. Together with Manfred
Fahle (Bremen, Germany) we also studied shape deformations of moving contours
(Zanker etal 1999). Recently this area of research was extended into the question
of 3D shape, studying how shadows affect the perceived length in the Muller-Lyer
and Judd illusion.
- Aesthetic choices and product design. Preferences
of human observers for simple shapes and compositions (object arrangements)
are investigated by applying interactive methods (such as eye scanning patterns)
in combination with evolutionary
algorithms that are used as otimisation technique to assess aesthetic
choices objectively. Such methods are helpful as psychophysical method to
explore multidimensional parameter spaces and can be used in product design
applications to investigate consumer choice (together with Tim
Holmes). Supported by EPSRC.
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a sample of recent publications
- Zanker, J.M.: Sensation,
Perception and Action - An Evolutionary Perspective. Palgrave Macmillan,
Basingstoke (2010)
- Hermens, F., R. Walker and, J.M. Zanker: Microsaccades and preparatory set:
a comparison between delayed and immediate, exogenous and endogenous pro-
and anti-saccades. Experimental
Brain Research 201 (3), 489-498 (2010)
- Zanker, J.M., F. Hermens and R. Walker: Quantifying and modeling the strength
of motion illusions perceived in static patterns. Journal
of Vision 10 (2): 13, 1-14 (2010)
- Meso, A.I. and J.M. Zanker: Perceiving motion transparency in the absence
of component direction differences. Vision
Research 49 (17), 2187-2200 (2009)
- Meso, A.I. and J.M. Zanker: Speed encoding in correlation motion detectors
as a consequence of spatial structure. Biological
Cybernetics 100, 361-370 (2009)
- Durant, S. and J.M Zanker: The movement of motion-defined contours can
bias perceived position. Biology
Letters 5, 270–273 (2009)
- Durant, S. and J.M. Zanker: Characterizing motion contour detection mechanisms
and equivalent mechanisms in the luminance domain. Journal
of Vision 9 (1): 36, 1-16 (2009)
- Holmes, T. and J.M. Zanker: Eye on the prize: Using Overt Visual Attention
to Drive Fitness for Interactive Evolutionary Computation. in Proceedings
of GECCO’08, 1531-1538
(2008)
- Durant, S. and J.M. Zanker: Combining direction and speed for the localisation
of visual motion defined contours. Vision
Research 48 (8), 1053-1600 (2008)
- Zanker, J.M.: Animal Communication: Reading Lizard's Body Language in Context.
Current Biology 17 (18),
R806-R808 (2007)
- Felisberti, F. and J.M. Zanker: Attention modulates perception of transparent
motion. Vision Research 45 (19),
2587-2599 (2005)
- Zanker, J.M.: A computational analysis of separating motion signals in transparent
random dot kinematograms. Spatial
Vision 18 (4), 431-445 (2005)
- Zanker, J.M. and J. Zeil: Movement-induced motion signal distributions in
outdoor scenes. Network:
Computation in Neural Systems 16 (4), 357-376 (2005)
- Zanker, J.M. and A.-al-J. Kane Abdullah: Are size illusions in simple line
drawings affected by shading ? Perception
33, 1475 - 1482 (2004)
- Zanker, J.M. and R. Walker: A new look at Op art : towards a simple explanation
of illusory motion. Naturwissenschaften
, 75-94 (2004)
- Zanker, J.M.: Looking at Op Art from a Computational Viewpoint. Spatial
Vision 17, 75-94 (2004)
- Zanker, J.M., M. Doyle and R. Walker: Gaze stability of observers watching
Op Art pictures. Perception 32, 1037-1049
(2003)
- Zanker, J.M. and J.P. Harris: On temporal hyperacuity in the human visual
system. Vision Research 42, 2499-2508
(2002)
- Zanker, J.M. and J. Zeil (eds): Motion
Vision: Computational, Neural and Ecological Constraints. Springer Verlag,
Berlin Heidelberg New York, (2001)
- Fisher, N. and J.M. Zanker: The Directional Tuning of the Barber Pole Illusion.
Perception 30, 1321-1336 (2001)
- Zanker, J.M. and N.R. Burns: The interaction of first- and second-order
direction in motion-defined motion. J.
Opt. Soc. Am. A 18, 2321-2330 (2001)
- Pix, W., J. M. Zanker and J. Zeil: The optomotor response and spatial resolution
in the visual system of male Xenos vesparum (Strepsitera). J.
Exp. Biol. 203, 3397-3409 (2000)
- Patzwahl, D. R. and J. M. Zanker: Mechanisms of human motion perception:
combining evidence from evoked potentials, behavioural performance, and computational
modelling. European Journal of Neuroscience
12, 273-282 (2000)
For further information you may look at the full publication
list ...
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and here is something about current teaching...
course co-ordinator for PS1061 Sensation and Perception
this
course is based on a brand new textbook:
Zanker,
J.M.: Sensation,
Perception and Action - An Evolutionary Perspective. Palgrave Macmillan (2010)
supervision of Third Year Research Projects PS3200
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lecturer on MSc course PS5102 Foundations of Neuroscience
- lecture
4: Sensory Systems I : Structure & Function
- lecture
5: Sensory Systems II : Sensory-Motor Integration
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and more about previous teaching...
course co-ordinator for third year option PS3060 Perception and Action
- lecture
1: introduction - basics of sensory-motor control
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lecture 2: look from the cockpit of a fly - the ecology of navigation
- lecture
3: driving a vehicle: controlling heading, avoid collision, braking
- lecture
4: cricket: how to hit a ball that can’t be seen
- lecture
5: bio-robotics & neuro-engineering
course co-ordinator for PS1020C Cognitive Psychology I until 2003 (old
version)
course co-ordinator for PS2020A Cognitive Psychology II in
2000/2001 (old version)
teaching some second-year PS2080 Conceptual Issues in Psychology
teaching some third-year PS3080 Philosophical Psychology
teaching some first- and second-year Research Methods in 2000-2002 (old
version)
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Brain & Behaviour
Research Group >> Vision
Research
Department of Psychology
<< Royal Holloway, University of London
Egham, Surrey TW20 OEX
ENGLAND
email: j.zanker@rhul.ac.uk
tel: +44 1784 443521
fax: +44 1784 434347
last update
02-Nov-2010
