Illusory Depth Based on Interactions Between Fluorescent and Conventional Colours: A Case Study on Frank Stella’s Irregular Polygons Paintings

Although Frank Stella intended to create flat, illusion-less Irregular Polygons paintings, it is not uncommon to experience the illusion of colour depth, based on the interaction between their fluorescent and conventional colours. Some critics praised these artworks’ flatness, while others described odd depth experiences that they categorised as a new kind of illusion. In order to provide a correct reading of these works and to reassess their art historical significance, a scientific case study regarding this colour-depth effect imposes itself. This article discusses an experiment in which we determined whether twenty artists, twenty art historians and twenty laypeople experienced fluorescent colours as protruding, receding or flat in combination with conventional colours. We additionally looked at whether they still perceived colour depth when all fluorescent colours were replaced with their conventional variants. All participants observed fifteen designs, which they had to rate according to the perceived depth of each coloured region with a number between −3 (strongly receding) and +3 (strongly protruding). The results revealed that most participants experience fluorescent regions as strongly protruding, unlike all conventional colours, which were rated as much less protruding. When a fluorescent colour was swapped with a conventional variant, all participants experienced significantly less depth. The differences between the subject groups were statistically negligible when looking at the mean depth ratings for both colour types. However, we discovered that artists experienced more contrast effects, as they gave different ratings to different panels (of identical colour and shape) in the same design, depending on their position.