Contemporary art critics recognize this as the point where she moved away from perspective and naturalism in her art. Around the same time, cubist works were being shown in Paris and Robert had been studying the colour theories of Michel Eugène Chevreul; they called their experiments with colour in art and design "simultanéisme". Simultaneous design occurs when one design, when placed next to another, affects both; this is similar to the theory of colours (Pointillism, as used by e.g. Georges Seurat) in which primary colour dots placed next to each other are "mixed" by the eye and affect each other. Sonia's first large-scale painting in this style was "Bal Bullier" (1912–13), a painting known for both its use of colour and movement.