New indices to characterize drawing behavior in humans (Homo sapiens) and chimpanzees (Pan troglodytes)

The field of Social Sciences has shed light numerous mechanisms associated with the development of drawing behaviour in humans. Analysis and interpretations relate, in general, to the final productions and the interpretation that the drawer, often a child, does. The nonfigurative marks produced by toddlers were often considered random, resulting from simple motor pleasure. Human is not the only one to display this drawing behaviour which is also found in other primates in captivity. Regarding drawings made by great apes such as chimpanzees, previous studies tend to show an interest in drawing, followed by complete disinterest once production is complete. Their achievements are often compared to the doodles of toddlers.

But does the absence of figuration necessarily mean absence of intention and representativeness? How to proceed when the drawing comes from toddlers or species unable to express themselves about what they produce?

Rather than reading a drawing, what if we decipher it?

In the article published in Scientific reports, Lison Martinet (University of Strasbourg), Cédric Sueur (CNRS-University of Strasbourg), Marie Pelé (Catholic University of Lille), Jérôme Hosselet (University of Strasbourg), Tetsuro Matsuzawa and Satoshi Hirata (Kyoto University) develop a fractal index giving access to the efficiency of drawings thus helping to decipher and understand them without questioning the producers.

The researchers collected sketches made on a touchscreen by children, human adults and chimpanzees. They then treated trajectories of the drawing in the same way as the trajectory of an animal moving through its environment. The mathematical fractal index that results from these analyses turns out to be lower when the outlines tend to be random, and higher when it is goal-oriented. Results highlight a difference between drawings produced by chimpanzees and those made by all humans, including 3-year-old children. Moreover, differences between age groups were noted in humans. Thus, as they grow older, children seem to gain in representational efficiency, their accomplishments going straight to the point, without any unnecessary additions. On the other hand, adults have a lower index and therefore reduced effectiveness due to the addition of numerous details that are not useful for understanding the drawing.

The authors conclude that drawing mathematical indices can emerge as a new tool thanks to touchscreens. This new line of research seems promising for identifying drawing behaviour, both in its evolutionary and ontogeny dimension.

Image Credit: Marie Pelé