reveals people overestimate slopes, heights
three illustrations show the importance of proportions in
large-scale form, according to Dennis Proffitt's research,
which reveals that people overestimate slants and heights.
The Rotunda (left) and an original drawing by Thomas Jefferson
(center) illustrate how the elevation of the building is based
on a circle embedded in a square (right). The illustration
appeared with an article, titled "Seeing Big Things: Overestimation
of Heights is Greater for Real Objects than for Objects in
Pictures," in the July issue of Perception.
Ida Lee Wootten
hill? It's probably not as steep as you think.
Hills appear steeper than they actually are. For example, everyone
judges hills with only a seven-degree slant as extremely steep.
The tendency to overestimate steepness is even greater for elderly
people, people carrying a heavy load and people who are tired,
of low fitness or in poor health.
are part of the first systematic studies on people's perception
of common geographical inclines. Led by psychology
professor Dennis R. Proffitt, the research results were published
recently in the national periodical, Journal of Experimental Psychology:
Human Perception & Performance.
from being a problem, the exaggeration of slant perception actually
helps people ascend hills, said Proffitt, who noted that earlier
work showed that overestimates of pitch are even more pronounced
when people view steep hills from the top rather than the bottom.
overestimates are functional. They help people pace themselves
when ascending hills and may even prevent people from undertaking
climbs that would be too difficult. In a similar vein, as anyone
in San Francisco can tell you, descending steep hills is difficult.
So overestimates encourage people to be cautious," he said.
a series of experiments on perceptual bias, participants consistently
judged a hill with a 10-degree slant to be about 30 degrees. Their
guesses for a five-degree hill averaged 20 degrees. When told
that their estimates were off by more than 15 degrees -- and that
by law the steepest public road in Virginia can have no more than
nine degrees in inclination -- most participants were incredulous.
look at a 10-degree hill, typically judged to be about 30 degrees
by verbal estimates and visual matching, and to be told that it
is actually 10 degrees is an astonishing experience for anyone
unfamiliar with the facts of geographical slant overestimation,"
said Proffitt, who holds U.Va.'s Cavalier Distinguished Teaching
the experiments, 130 U.Va. students reported their judgments of
inclines in three different ways. A verbal report was a simple
estimate in degrees of the hill's incline. Participants made reports
while standing at the base of hills, looking directly ahead at
them. To gain a visual estimate, participants used a disk with
an angle that could be adjusted to represent the hill's incline.
Judgments based on touch (called "haptic judgments")
were made by using a tilt board with a flat palm rest, the tilt
of which could be adjusted to match the inclination.
experiments were conducted. They showed that hills appear steeper
when people carry a heavy load, are fatigued by running, are not
physically fit, are elderly or in poor health. The verbal and
visual judgments grossly overestimated incline, while haptic judgments
were significantly more accurate.
The study participants' verbal and visual overestimates reflect
their awareness of how challenging hills can be to climb, Proffitt
believes. "The highly exaggerated estimates of slant show
that human perceptions are not simple reflections of reality,
although most people tend to assume they are," he said. "However,
the visually guided actions, reflected in the haptic response,
are accurate and unaffected by fatigue, load, fitness, age and
other experiments investigating how people perceive heights, U.Va.
researchers found that the larger real objects are outdoors, the
greater is the overestimate of their height. The findings were
published in the July issue of the national journal, Perception.
studies, involving 230 U.Va. students, investigated why people
experience very small vertical-horizontal distortions when viewing
photographs and line drawings, but tend to vastly overestimate
vertical extent when viewing real objects outdoors. For example,
when viewed in person, the Rotunda appears elongated vertically
when compared to Thomas Jefferson's illustration showing the building's
horizontal and vertical dimensions are physically equal.
In six experiments with the 230 students, participants viewed
objects presented in line drawings or in photographs and found
that there was only a small overestimation of their vertical extent.
These same objects were also viewed in an outdoor setting and
in a 3D virtual reality scene shown in a head-mounted display.
In these situations the vertical overestimation was about twice
as large as that found when viewing the two-dimension images.
"As with the studies on geographical slant, these findings
demonstrate that our everyday perceptions often exhibit large
distortions of which we are generally unaware," Proffitt