EYE TRACKING RESEARCH
Primate Research
& eye tracking
Customer
Primate Research Institute
Kyoto University
Eye tracking enables studies on
differences and similarities in human and
chimpanzee face scanning
The vast amount of eye contact interaction seen in human beings has been of
interest for a long time. This study is a way to understand how far back in
evolution that behavior can be traced by looking at man’s closest relative, the
chimpanzee. By using eye tracking to study gaze and face scanning, scientists
are able to determine how and what individuals look at, how they collect
information from faces, and understand more about the evolution of man.
Tools & methods
Objectives
Dr. Kano and Dr. Tomonaga used a Tobii
X120 Eye Tracker to conduct these experiments, collecting accurate eye tracking
data without limiting the subjects’ freedom
of movement.
Studying and determining
face scanning patterns in
chimpanzees with spatial
(what) and temporal (order)
characteristics, then
comparing them to those of
humans.
Tools & methods
With Tobii X120, Dr. Kano
and Dr. Tomonga at Kyoto
University tracked the eye
movements of chimpanzees
and humans examining
pictures of chimpanzee,
human and mammal faces. In
this 2-experiment study, they
explored the difference in
scanning neutral faces and
faces expressing emotions.
Results
The study gave great insight
into the field of primate face
scanning, and determined a
difference in the way humans
and chimpanzees fixate on a
face. While chimpanzees
mainly focused on the mouth,
humans fixated on the eyes,
describing the difference in
how the two species scan
faces and assess emotions.
Background
The Primate Research Institute at Kyoto
University has studied the behavior and
cognition of non-human primates for several
years. By studying mankind’s closest relative, Dr. Kano and Dr. Tomonaga at Kyoto
University aim to understand emotional
expression and detection. They enlisted the
help of the 14 chimpanzees at the Kyoto
facility to do so.
Research objectives
In the first experiment, six chimpanzees and
18 humans (Japanese students) looked at
72 color photos of faces of humans, chimpanzees and other mammals. The tests
were divided over ten sessions to keep the
chimpanzees motivated, who were rewarded with apple slices for participating.
In the second experiment, five chimpanzees
and nine humans looked at 24 random
photos of human and chimpanzee faces
expressing standard human emotions; happiness, excitement, fear, anger, etc. The
chimpanzees and the humans were all
highly familiar with faces of both species
and never responded with fear to the photos.
Unlike previous studies of how non-human
primates view faces, this study targeted the
comparison between chimpanzees and
humans with regard to face scanning; the
different patterns of scanning, dependence
on facial expression, and which factors
contribute to the detected patterns’ characteristics.
Conclusions
Both species have similar facial expressions,
but there are still vast differences between
the way chimpanzees and humans interact.
There are also major differences in the muscular face structure. Where humans make
subtle expressions with the eye area, chimpanzees instead possess equivalent motor
control and musculature around the mouth.
Both species focused more on the face
than on any other part of the photo, the
eyes being the initial target for both chimpanzees and humans. Secondary fixation
was in both cases the mouth, the main
difference lying in the fixation duration on
the eyes. Humans looked much longer at
the eyes than did chimpanzees who quickly
moved their gaze to the mouth area. Hu-
In the application created with Tobii Software Development Kit (SDK), areas of interest (AOI) were defined, dividing the face
into sections to further analyze fixations and
saccades for these areas.
“Chimpanzees often move their heads and even leave during
experiment sessions! Tobii’s quick and long-lasting system
calibration procedure greatly helped in acquiring accurate
and reliable recordings of such individuals.”
– Dr. Kano, Primate Research Institute, Kyoto University
This is the latest study from the
Primate Research Institute at Kyoto
University. Previous studies have
explored chimpanzee detection of
social cues in conspecific and non
conspecific species using eye
tracking. They have 14 chimpanzees
at the Institute right now: three young
chimpanzees, eight adults and three
elderly chimpanzees.
mans were more likely to re-fixate on the
eyes, creating a triangular gaze pattern,
whereas chimpanzees were less likely to
fixate on the eyes at a later stage. For both
species, the main features (eyes, nose, and
mouth) were the vital fixations, except in the
case of chimpanzees viewing mammal
faces where other parts (like the lion’s mane
or the rhino’s horn) attracted more interest.
chimpanzee
human
“Indeed, it is ethically
and technically impossible to restrain
chimpanzees for eye
tracking. Tobii’s techGaze plot describing the face scanning patterns of chimpanzees vs humans in neutral
nology eliminates the
faces. Both showed an initial focus on the eyes but unlike humans, chimpanzees
necessity of restrainquickly shifted the focus towards the mouth.
ing them. This is one
gaze patterns depending on the facial exof the main reasons why we use Tobii’s
pression in front of them, yet with distinct
solution and how we could successfully
fixation on the mouth. Humans, however,
conduct eye tracking experiments in nonremained intensely focused on the eyes,
human great apes.” – F. Kano, Primate
regardless of facial expression.
Research Institute, Kyoto University.
This would indicate that chimpanzees and
humans have very specific facial eye scanning patterns, that are in fact so different
that what we today know as human lengthy
eye contact interaction would have appeared at a later stage in evolution.
References
Why Tobii?
To find out how eye
tracking can improve
your research, please
visit www.tobii.com or
contact one of our
offices.
“With Tobii Technology’s solution, we are
able to acquire eye movement data in chimpanzees as accurately as that in humans
(average error of approximately 0.5 degrees). This is reliable enough for most of
the research we have conducted and intend
to conduct in future.”
Kano, F., Tomonaga, M., Face scanning in
chimpanzees and humans: continuity and
discontinuity, Animal Behavior (2009),
doi:10.1016/j.anbehav.2009.11.003
Aside from reliability, working with chimpanzees presents challenges in itself, such as a
chimpanzee
The Primate Research Institute was
founded in 1967 under the direction
of Kinji Imanishi (1902-1992),
world-renowned scientist and father
of Japanese primatology. Working
towards understanding the biological,
behavioral and socio-ecological
aspects of primates, they seek the
origin and evolution of man. The
Language and Intelligence Section
aims to understand the higher
cognitive functions in the great apes,
especially in the chimpanzee, humans’
closest relative. Both experimental
and observational approaches
illuminate the similarities and the
differences between human cognition
and ape cognition. All chimpanzee
research at the Primate Institute at
Kyoto University is non-invasive.
human
Name: Primate Research Institute
Web: www.pri.kyoto-u.ac.jp
Location: Kyoto, Japan
chimpanzee leaving
the test site for lack
of interest or the
ethical issue of scientific research involving animals.
In the second experiment, the researchers
found that the chimpanzees altered their
Second study; Gaze plot describing the face scanning patterns on human and chimpanzee faces depicting standard
emotions. Main chimpanzee focus lies on the mouth with a slight adaption to the expression, whereas humans
remained focused on the eyes.
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