University of Padua, Italy
Corresponding author details:
Franco Viviani
Department of Biomedicine
University of Padua
Italy
Copyright: © 2020 Viviani F. This is an openaccess article distributed under the terms of the Creative Commons Attribution 4.0 international License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
A visit in a karst area, rich in wall representations, stimulated the present work. Physical
activity performed in harsh but delightful environments can provide, by serendipity, useful
ideas. During the observation of a depicted babirusa (or a pig-deer, Babirousa celebensis)
in a Sulawesian cave, Indonesia, a philosophical conundrum, till now unresolved, came
in mind: how is possible that some signs on a wall can exactly represent that particular
animal? Thanks to the use of the predictive model of perception and the mechanism of
predictive coding, recently proposed in perception studied, the perspective can be widened.
These models, in fact, challenge the classic vision (bottom-up model), suggesting that vision
is the simultaneously result of a bottom-up and a top-down processing. Therefore, sensory
information is a sort of feed-back on our expectations that could be constantly corrected
and refined. Using this frame, it is possible that the first rock paintings became vivid only
when, by trials and errors, the painters’ predictions about the real mammalian dovetailed
enough with the conjectures that was possible to infer from the painting in the wall. The
conundrum is not solved, of course, but if the predictive processing will be completely
ascertained, it will offer a key to deepen it.
Visual representations; rock art; Sulawesi; theoretical problems
I recently visited in Sulawesi (Maros Karst area, Indonesia) a cave whose details were
reported by an anthropo-speleological team decades ago [1-3]. This area is becoming
extremely important due to the discovery of the ancient wall representations, some of
them showing hunting scenes in prehistory [4]. Observing the details of those painted
caves [Figures 1 and 2]; a philosophical conundrum was constantly acting in my mind: if a
babyrusa (Babyrousa celebensis) or a deer-pig belonging to the swine family is represented
on a wall, how is it possible that the painting of that animal could depict exactly that
pig-like mammalian? To reach this goal it is in fact required that the space showing that
animal is signed in a specific way, something probably outside the painter’s awareness. In
other words: what is the correct way to let that a drawing would be interpreted as being
a babyrousa by the majority of the observers once completed? In that wall, in fact, we
do not see it as if it was in its environment and, more intriguing, it’s not even true that
looking that picture, it is as if we were looking a babirusa, because what we are seeing is a
mixture of traits in a surface. What is, in short, that makes special the experience of seeing
an animal in a painting? If representation is a modality that man has contrived to use signs
that are replacing something else, the signs should be arranged in space in a peculiar way,
to express relations permitting a semantic construction. That is, of course, strictly related
to the social and cultural background of the creator [5,6]. Representation is an extremely
flexible concept, mainly studied by aestheticists and semioticists but, in its crude essence,
it is connected to the way in which sensory information records how a physical object
is described in a medium. Therefore, to deepen the conundrum, cues could be inferred
by novelties found in perception studies: for example, the so-called predictive models of
perception, a conceptual computational model proposing that perception is able to predict
what is coming from our sensory inputs in order to reduce the prediction errors [7]. Till
not long ago, in fact, the classic vision suggested that perception was an open door to the
external reality because our sense organs’ receptors, sending signals from the body to the
brain, showed us the world as it is (bottom-up model). The role of the incoming signals
was to put in a context what was perceived. Modern theories assume that perception is
the result of the predictions that our brain can make on the basis of the arriving sensorial
inputs. In a nutshell, there is not only a flux of signal from the body to the brain, but also
one from the brain to the body (top-down processing): perception is not passive. This
because our brain, basing on its previous experiences, makes predictions on the incoming
signals. In the visual hierarchy there are different layers and predictions are made about
the layer below. The gap between the actual and the predicted inputs are sent up to thevisual hierarchy thanks to a mechanism called predictive coding,
with the aim to reduce the future prediction errors. Clearly, using
this theoretical frame, sensory information is a sort of feedback on
our expectations, that could be constantly corrected and refined. The
balance between expectations due to our past learning and what is
currently sensed is extremely delicate. For some theorists, perception
becomes a “controlled hallucination” [8-11]. This because our
brains are constantly modifying their internal models of the world
surrounding us to let that the external environment is in accordance
to the predictions that we concocted about it. So, not only perception
is involved, but also action and general cognition. At this point, it
is not difficult to image that a Sulawesi Palaeolithic “artist” was a
person who, based on the importance that a babyrousa assumed for the group s/he belonged to, was able to hatch a plan to imagine the
right signals ending in a represented pig-deer, probably for trials and
error at the beginning, to let that the animal came in line with her or
his predictions. Little by little, thanks to feedbacks with peers, when
the drawing was refined enough to be recognised and accepted by the
majority of her or his community members as a babyrousa without
hesitation, the painting was fixed in the cavern wall. This because
the predictions about the real mammalian detailed enough with the
conjectures that was possible to infer from the painting in the wall.
Ofcourse, the present Pindaric flight does not solve the conundrum,
it is just a reflection based upon predictive processing, a modality
that must be completely ascertained and more accurately verified.
But if perception, action and cognition belong to computations in the
brain due to bottom-up and top down processing, it could become
plausible.
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