It began simply
enough nearly two decades ago. When the professor of psychology
wanted to enhance students' learning experiences in his 300-level class
on perception, he introduced some visual aids — digital images of
seemingly innocuous geometric patterns.
Suddenly, students
discovered there's more than meets the eye.
But is there?
In the visual illusion
research of psychologist and artist D. Alan Stubbs, perception and
reality can be worlds apart. As a catalyst of illusion, digital art
helps to illustrate principles of perception. It also raises awareness
of the important distinction between physical and psychological
dimensions of stimuli that affect human behavior, including errors in
judgment.
As pilots flying at
night without instrumentation and outdoor enthusiasts caught in
whiteouts know all too well, there are times when our senses deceive us.
Or, to put it another way, a dual reality seems to exist. And that, says
Stubbs, gets to the truth of illusions.
"Illusion is something
that's not quite the same as you think it is," says Stubbs, a University
of Maine professor of psychology and an adjunct faculty member in the
Department of Art. "For instance, all photos are illusions. The picture
on the paper is not your Uncle Henry, but light or marks similar to what
you see when you look at him. Put a CD in and the music sounds like
whomever. That's an illusion."
Some illusory images,
like those Stubbs creates, might seem to be examples of misperception.
Instead, Stubbs views them as mechanisms for understanding how the
perceptual process works. That's particularly important, because
perception is a strong influencer of human behavior.
"Perception is
fundamental," he says. "If you can't perceive, where is cognition going
to come from? You perceive, act and know. They can't be separated. As I
study it, perception is directly gathering information about the world."
Stubbs' research has evolved from the study of time perception in
animals to graph and image perception in humans. It dovetails into his
decades-long passion for photography that began concurrently with his
graduate research. For Stubbs, the science of perception informs his art
and vice versa.
In the 1970s, Stubbs
was using pigeons to study perception learning and behavior, as well as
visual cognition. In particular, he explored how pigeons tell time.
Then, almost a decade
ago, Stubbs turned his focus to another form of perceptual learning.
"I started doing a lot
of graph experiments in front of a computer screen," he says. "That's
where I became the pigeon."
With UMaine psychology
colleague Laurence Smith, Stubbs studies graphical perception, or how
people extract information from data graphs to draw conclusions. The
psychologists examine the accuracy of people's graph-based judgments, as
well as biases resulting from the graph formats or the viewers'
expectations. They also consider what pertinent details are needed in
graph design to effectively communicate to produce sound, informed
judgments.
The research is
similar to Stubbs' work in image perception, which had its start in the
classroom where he sought to bring the perceptual process to life for
his students. Using PhotoShop software, Stubbs took one-dimensional
blackboard drawings and created his own 3D digital images that not only
convey psychological principles of perception, but give the illusion of
increased and decreased brightness — and even movement.
"Students find the
images fascinating because of the ‘wow' factor, but I use them to make
points. Even as they seem to deceive us, illusions give us a good truth
about how the visual system works."
After a decade of
creating the research-based visual aids, Stubbs has amassed a collection
of original digital art that he now exhibits for the public. He admits
that in the creation process, only one in 10 of his illusion images
"turns out." But most important, those that do lead him to other
questions about perception.
"I found I actually
learn more about the phenomenon by creating the images," he says.
One of Stubbs' digital
art pieces, Dynamic Luminance-Gradient Effect, was deemed one of the Top
10 Best Visual Illusions of the Year in 2006 by the international Vision
Sciences Society.
This year, Stubbs
teamed with recent Ph.D. student Simone Gori of the University of Padua
to create an image that was used as the logo for the 2007 Vision
Sciences Society conference in May.
Dynamic
Luminance-Gradient Effect — lines that meet in the center where a
gradation of color or light is apparent — "works" by having the viewer
physically move closer to and away from the image. Move toward the
center and the image appears to brighten, giving a "here comes the sun"
effect.
In other images,
shaded areas among the bars and lines in his artwork appear to move,
grow or shrink, depending on the distance between a viewer's eye and the
image.
"It is an illusion in
that nothing is changing. Nothing is getting brighter. There is only
apparent motion. The illusion has to do with what's happening across the
eye," Stubbs says. "It's not a tricking; it just looks like the image is
brightening when it's not."
Part of the reason
such illusions work, says Stubbs, is the retina receives increasing and
decreasing light. Moving closer to a figure with a brighter center
causes a person to see less in the periphery, while every point on the
retina receives more light.
Gradation of the
boundaries — graded change of luminance — appears to be a key to the
illusory effect. "One explanation of this effect could be that these
patterns, with gradients of luminance change, suggest to our visual
system the presence of an optic flow, like a tunnel with a light at the
end," wrote Stubbs and Gori in the journal Perception.
In a sense, our visual
system misinterprets the image, behaving as if it were a 3D physical
situation instead of a two-dimensional pattern.
"All of these illusory
effects show the importance of the distinction between the physical
dimension and the psychological between luminance and brightness,"
explained Stubbs, writing in High Resolution, a specialty newsletter for
the displays industry. "Without it, we can make errors in judgment and
think that there is a physical aspect for what we see when, in fact, we
are being influenced by psychological aspects."
by
Margaret Nagle
