Objects from the Middle Paleolithic period colored with ochre and marked with
incisions represent the beginning of non-utilitarian object manipulation in
different species of the Homo genus. To investigate the visual effects caused
by these markings, we compared humans who have different cultural backgrounds
(Namibian hunter–gatherers and German city dwellers) to one species of non-
human great apes (orangutans) with respect to their perceptions of markings on
objects. We used eye-tracking to analyze their fixation patterns and the
durations of their fixations on marked and unmarked stones and sticks. In an
additional test, humans evaluated the objects regarding their aesthetic
preferences. Our hypotheses were that colorful markings help an individual to
structure the surrounding world by making certain features of the environment
salient, and that aesthetic appreciation should be associated with this
structuring. Our results showed that humans fixated on the marked objects
longer and used them in the structural processing of the objects and their
background, but did not consistently report finding them more beautiful.
Orangutans, in contrast, did not distinguish between object and background in
their visual processing and did not clearly fixate longer on the markings. Our
results suggest that marking behavior is characteristic for humans and evolved
as an attention-directing rather than aesthetic benefit