Border Elements Deter Shape-from-shadow via Negative Polarity, Not Motion, Not Color Annual Meeting of the Psychonomic Society, Minneapolis, MN, November 18

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Border Elements Deter Shape-from-shadow via
Negative Polarity, Not Motion, Not ColorAnnual
Meeting of the Psychonomic Society, Minneapolis,
MN, November 18 21, 2004John M. Kennedy
Juan Bai University of Toronto
Color and Shape-from-shadow Percept
Lines, Surfaces, and Shadows
Shadow and Dark Line
Possible Segregations along a Border
Conclusions
Color and Shape-from-shadow Percept
Contour reflectance change on a surface
A Hering line added along a shadow border may
have impaired shape-from-shadow perception
because of negative polarity of its contour
bordering the shadow.
We see objects by means of their surfaces, and
source of illumination.
A line has two contours, one on each side
There are different figure-ground combinations
when two regions share a contour or a line
(Kennedy, 1974 Peterson, 1991)
Lines copying surface borders give us surface
edge impressions (e.g., the hill, the roof of the
house adapted from Kennedy, 1988).
Among the list of 8 possible borders in pictures,
only luminance polarity matters for shadow
borders in shape-from-shadow perception, not
stereo (Kennedy Bai, 2004), and (as shown here)
not color and not motion.
surface borders
This favors a perceptual theory (see Cavanagh
Leclerc, 1989) over figure-ground attention in
explaining Herings ringed shadow effect.
a
b
figure-ground percept along a contour (adapted
from Rubin, 1915/1958)
figure-figure percepts along a contour
a
b
A red line does not prevent shape-from-shadow
perception as long as the luminance goes
dark-to-light from shadow to line and to
non-shadow (a).
References
But shadows without penumbras (a, adapted from
Mooney, 1957) work well in showing a girls face,
and dark lines in (b) impair perception of the
face.
shadow border
Cavanagh, P., Leclerc, Y. G. (1989). Journal of
Experimental Psychology Human Perception and
Performance, 15, 3-27. Goldstein, B. (2002).
Sensation and Perception (6th ed.). Pacific
Grove, Calif. Wadsworth-Thomson
Learning. Hering, E. (1964). Outlines of a
Theory of the Light Sense (L. M. Hurvich D.
Jameson, Trans., pp. 8). Cambridge, MA Harvard
University Press. (Original work published
1874). Kennedy, J. M. (1974). A Psychology
of Picture Perception. San Francisco
Jossey-Bass. Kennedy, J. M. (1988). Paper
presented at the Psychonomics Society
Conference, Chicago, IL. Kennedy, J. M. (1993).
Drawing and the Blind. New Haven Yale Press.
Kennedy, J. M. Bai, J. (2000). Perception, 29,
399-407. Kennedy, J. M., Bai, J. (2004).
Perception, 33, 653-665. Kennedy, J. M.,
Juricevic, I., Bai, J. (2003). In H. Hecht, R.
Schwartz, M. Atherton (Eds.), Looking into
Pictures An Interdisciplinary Approach to
Pictorial Space (pp. 321-354). Cambridge, MA MIT
Press. Mooney, C. M. (1957). Canadian Journal of
Psychology, 11, 219-226. Peterson, M. A. (1999).
Journal of Experimental Psychology Human
Perception and Performance, 25, 276-286. Rubin,
E. (1958). In D. C. Beardslee (Eds.), Readings in
Perception (pp. 194- 203). Princeton, NJ Van
Nostrand. (Original work published 1915).
In comparison, the same red line blocks
shape-from-shadow perception if it is darker than
the shadowed region and hence creates negative
border polarity (b).
However, a line copying a shadow border does not
give us the impression of the darkness of the
shadow (e.g., the houses shadow on the ground
adapted from Kennedy, 1988).
Note that the shadowed area in (b) is darker than
the illuminated region (Cavanagh Leclerc,
1989), yet shape-from-shadow perception is
diminished.
figure-figure percepts along a line (adapted
from Kennedy et al., 2003)
ground-figure-ground percept along a line
(adapted from Kennedy et al., 2003)
figure-ground-figure percepts along a line
Motion and Shape-from-shadow Percept
Border-polarity Hypothesis
Motion and Shape-from-shadow Percept
Kinds of Borders
Herings Ringed Shadow
There are 8 kinds of borders that can cause
perception of surfaces, combined from
luminance/spectral, monocular/binocular, and
static/moving borders (Kennedy, Juricevic, Bai,
2003).
penumbra
umbra
Shadow borders are luminance borders that may
convey information about surface shapes, e.g.,
the elderly face in (a, adapted from Mooney,
1957), which resembles the photo in (b).
a

a
b
c
d
a
b
c
Apparent shadow-border motion resulting from
rapid alternations of (a) and (b) allows
shape-from-shadow perception of the elderly face,
possibly due to positive border polarity. This
is in accordance with what the border-polarity
hypothesis predicts!
Both negative (a) and Hering-dark-line (b) have
negative contours (i.e., light-to-dark from
shadow to non-shadow), and both fail to show the
elderly face in positive (c).
Acknowledgements
b
The direction of luminance change can be called
polarity.
The authors would like to extend special thanks
to Humera Iqbal, Dr. Allison Sekuler, Dr. Paul
Muter, Dr. Mark Schmuckler, Dr. Hiroshi Ono, and
Igor Juricevic. We dedicate this poster to
Rudolf Arnheim in honor of his 100th birthday,
July 15, 2004. kennedy_at_utsc.utoronto.ca
By contrast The same shadow-border motion
resulting from alternations of negatives (c d)
does not give us the impression of the same face,
possibly due to negative border polarity. This
is again in accordance with what border-polarity
predicts!
Hering (1874/1964) said a shadow with a
borderline looks like a stain. He contended that
for a cast shadow (a, after Goldstein, 2002),
shadow perception fails in (b) because the
penumbra is lost to the dark line surrounding the
umbra.
It may be the dark lines negative contour
bordering the shadow in (b) that diminishes
shape-from-shadow perception a
border-polarity hypothesis that was supported
by Kennedy and Bai (2000, 2004).
c
b
a
But lines in (c, adapted from Kennedy, 1993) do
not give us the impression of the dark shadow and
the elderly face.