Outline of the symposium
Visual
regularities like bilateral symmetry have a great impact on the way in
which humans and animals experience and influence the world around
them. For instance, humans and animals
prefer symmetrical mates and bees prefer symmetrical flowers, thus
causing
a convergence on symmetrical forms in nature. But what is so special
about
symmetry? Does symmetry have specific intrinsic properties which made
it
almost inevitable that symmetry became an evolutionary relevant
regularity?
Has the symmetry preference been selected evolutionary because the
degree
of symmetry in the form of an organism indicates its quality? Or is the
symmetry preference a consequence of visual systems being very
sensitive
to symmetry? But, then, how sensitive are visual systems to symmetry,
and
what are the mechanisms underlying symmetry processing? These and other
questions will be addressed during the symposium which focuses on
mathematical,
biological, psychological, and neurophysiological research into the
principles
of symmetry perception.
Presentations
The Holographic
Structure of Symmetry
Peter van der Helm
Nijmegen Institute for Cognition and
Information,
P.O. Box 9104, 6500 HE Nijmegen, The Netherlands
Abstract:
Regularities in stimuli are
generally thought to reflect something
meaningful about objects or events in the external world. However,
although
many kinds of regularity can be imagined, visual systems are sensitive
to only a few regularities, among which bilateral symmetry. In this
talk
I argue that the intrinsic 'holographic' structure of symmetry forms
the
basis of its special status in not only perception but also in e.g.
molecular
biology. The formal concept of holography is closely related to a
concept
of growth, and provides a rich conceptual framework for detailed
empirical
research into many specific aspects of symmetry perception.
The Evolution of
Symmetries in
Biological Signals
Magnus Enquist
Ethology, Department of
Zoology, University of Stockholm, S-106 91 Stockholm, Sweden
Abstract: This
talk reviews the
various explanations that have been offered for the evolution of
symmetries in biological
signals. Symmetrical signals may have favoured signallers because such
signals look the same from different viewpoints. Another possibility is
that receivers react more strongly to symmetries. This may be a
by-product
of how the brain operates. For example, viewing objects from many
angles,
symmetries in the neural machinery itself or a generally symmetrical
world
could all contribute to such a bias. It has also been suggested that
preferences
for symmetry may actually entail a benefit to the receiver and for
example
allow a female to choose a better male with whom to reproduce.
Specialized
Processing for Symmetry in the Human Brain: Psychophysical and fMRI
Evidence
Christopher Tyler
Smith-Kettlewell Eye
Research Institute, 2318 Fillmore Street, San Francisco, CA 94115, USA
Abstract: Perception
of visual
symmetries is of high aesthetic importance given their ubiquitous role
in objects of human construction. Previous
work implied that bilateral symmetry perception occurs mainly near the
symmetry axis. We show that this result is attributable to the pattern
spatial scale. Patterns scaled appropriately may be seen equally across
the entire visual field, unimpaired by total removal of the axis
region.
These results suggest specialized brain mechanisms for symmetry
processing
rather than long-range interactions in primary cortex. Indeed,
functional
MRI studies showed little symmetry-related activity in areas V1-V5, but
a strong, non-retinotopic response in the Middle Occipital Gyrus
specific
to pattern symmetries in general.
Peter
A. van der Helm 