Speaker: Dr Alessandro Soranzo (SHU)

Alessandro is a Reader in Psychology within the College of Social Sciences and Arts at Sheffield Hallam University. His main area of interest lies in the Psychology of Perception, including; Colour and Illumination Perception, Visual Illusions, Perception and Art, Virtual Reality, and Robotics.

Title: Why the same colour can appear different?

Colour contrast is the condition whereby two surfaces with the same spectral composition are perceived to have a different colour when they are placed against backgrounds with different chromaticity. Although this phenomenon has been the focus of philosophical and scientific investigation for (literally) millennia, there is still little agreement on why it is happening. For example, it has been explained in terms of low-level (retinal) mechanisms; however, convincing evidences supporting more high-level, cognitive, interpretations have been presented over the few last decades. 

Two are the main high-level interpretations. On one side, the layer approach claims that the visual system splits the light reaching the eyes into separate overlapping layers, corresponding to separate physical contributions, such as illumination, colour and transparencies; whilst on the other side, the framework approach maintains that the visual system groups the different light intensities within a set of contiguous frameworks. By exposing new and old compelling lightness illusions, this presentation will highlight the pros and cons of both the high and mid-level approaches to colour perception and it will suggest that a combination of the two approaches would lead to a more comprehensive colour theory.