N E W S R E L
E A S E
November 12, 2003
The length of the gaze affects human preferences, new study shows
PASADENA, Calif.—Beauty may be in the eye of the beholder, but a new
psychophysical study from the California Institute of Technology
suggests that the length of the beholding is important, too.
In an article appearing in the December 2003 issue of the journal
Nature Neuroscience, Caltech biology professor Shinsuke Shimojo and his
colleagues report that human test subjects asked to choose between two
faces will spend increasingly more time gazing at the face till they
will choose that face as more attractive. Also, test subjects
will typically choose the face that has been preferentially shown for a
longer time by the experimenter. In addition, the results show
that the effect of gaze duration on preference also holds true for
choices between abstract geometric figures.
In sum, the findings show that human preferences may be more
fundamentally tied to "feedback" between the very act of gazing and the
internal, cognitive prototype of attractiveness than was formerly
assumed. Earlier work by other researchers has relied on the
"attractiveness template," which assumes that an individual's ideal
conception of beauty has somehow been imprinted on his or her brain due
to early exposures to other people's faces, such as the mother.
In fact, Shimojo says, the new results come from experiments especially
designed to minimize the influence of earlier biases and existing
preferences. Even when images of faces have been
computer-processed to eliminate possible biases due to ethnic origins
and even such trivial issues as hair-styles, the results still show
strongly that the gaze is subconsciously oriented toward the eventual
choice. This holds true even more strongly when a test subject is
asked to choose between two abstract geometric figures, suggesting that
the slightly lower tendency to fix the gaze on the eventual choice of
two faces is influenced by existing selection biases that cannot be
totally controlled.
The findings in Nature Neuroscience comprise two experiments. The
first was the choice of the more attractive face, in which all the test
subjects were asked to rate the faces from 1 (very unattractive) to 7
(very attractive). The average rating for each face was then
calculated so that faces in pairs could be matched in different ways.
In the "face-attractiveness-easy task" the faces were paired according
to gender, race, and neutrality of facial expressions, but comprised a
choice of a "very unattractive" face with a "very attractive"
face. Five test subjects were then shown 19 face pairs and were
asked to choose the face they preferred. A video camera
recorded the movements of their eyes as they directed their attention
from one face on the screen to the other.
The results showed that the likelihood of gaze of the test subjects
started from chance (50%) but rose above70 percent of their time
gazing at the face till they chose that face.
Even more striking was the difference in gaze devoted to the
"face-attractiveness-difficult task," in which 30 pairs of faces were
matched according to the closeness in which they had been ranked for
attractiveness. In this experiment, the test subjects spent up to
83 percent of their time gazing at the face they would choose
immediately before their decision response, suggesting that the gaze is
even more important when their is little difference in the features of
stimuli themselves.
The test subjects were also asked to choose the least attractive face,
as well as the rounder face, and the results also showed that the
length of the gaze was an important indicator of the eventual
choice. In addition, the subjects were asked to choose between
abstract geometric shapes, and the length of gaze also correlated
highly with the eventual choice.
The second experiment is "gaze manipulation," in which the faces are
not shown simultaneously, but in sequences of varying duration on the
two sides of the computer screen. In other words, one face was
shown for a longer time (900ms) than the other face (300ms), and as a
control, the faces were also shown to (other subjects) in the center of
the screen in an alternating sequence. The results show that the
face shown for a longer time tends to be chosen only at chance level
(50%) with only two repetitions of the sequence, but about 59
percent of the time with 12 repetitions. This suggests that the
duration of the gaze can influence the choice. Note however that this
manipulation did not work in the control experiment without gaze shift
as mentioned above, indicating that is not mere exposure time, but
rather active gaze shift that made the differences.
In sum, the results indicate that active orienting by gaze shift is
wired into the brain and that humans use it all the time, albeit
subconsciously, Shimojo says. One example is our preference for
good eye contact with people whom we are engaging in conversation.
"If I look directly into your eyes, then glance at your ears, you can
immediately tell that I've broken eye-contact, even if we're some
distance apart," Shimojo explains. "This shows that there are
subtle clues to what's in the mind."
In addition to Shimojo, the other authors are Claudiu Simion a graduate
student in biology at Caltech; Christian Scheier, a former postdoctoral
researcher in Shimojo's lab; and Eiko Shimojo of the School of Human
Studies/Psychology at Bunkyo Gakuin University in Japan. Shinsuke
Shimojo and Claudiu Simion contributed equally to the work.
Contact: Robert Tindol
(626) 395-3631
tindol@caltech.edu