Thurstonian scaling and the perception of painterly translucency

Abstract

Visual material perception is often studied with physically well-defined stimuli that lack ecological variety. Yet, even the visual variety found in our natural environment is limited when compared to artistic depiction. A similar object can be depicted in numerous different ways that all make visual sense. We studied the perception of translucency using 38 paintings of sea waves as experimental stimuli. It has previously been shown that translucency depends on the shape of the translucent object and on the light conditions. Both shape and light appear in many variations in depictions of seas. In the first experiment we explored the use of Thurstonian scaling and introduce the concept of Number of Distinguishable Levels (NDL). We found that the NDL ranged between 1.5 in a set with small waves to 4 in a set with large waves. While Experiment 1 took place in the lab, Experiment 2 was performed online and replicated the data from Experiment 1 qualitatively, although the NDL was lower in the online experiment. Furthermore, in this experiment we conducted Thurstonian scaling on a number of other attributes that possibly contribute to translucency perception, such as wavetip shading, surface reflections and realism. We found that many of these correlated significantly with translucency. In sum, this study advocates and demonstrates the use of uncontrolled stimuli, in our case paintings, to explore the wide variety of input the human visual system can process.