Red flower petal being guided by boy ~ 35min into the film

Roughly, at about 34-35 minutes into the film, there is a scene with a red flower petal floating through the air and a small boy in the background waving his arm. The flower petal is obviously reacting to the boy's movements... or vice versa. I am not interested in interpretations, it is obvious that the two are connected, or we, as human beings aim to connect them to establish an order in the universe. What I am actually interested in knowing is if anyone knows or could guess how this was done. After looking at it so many times it just looks so perfectly matched. Could the boy actually affect the petal in some way? It looks as though he is tugging on something, his movements are too precise to be uncoordinated and random. Could the petal be tied by some very fine string?