Li Li Tan (Cambridge) Visual Discrimination and the Perception of High-Level Features

There is an  extensive debate on whether the phenomenal character of our visual  experiences can include more than just “low-level” features like shapes,  colours, brightness and motion. Many philosophers claim that various  “high-level” features can also figure in visual experience. These  include sortal features (e.g. being a tree), facial expressions  (e.g. being happy), and affordances (e.g. being graspable). This  paper argues that we can determine what features figure in visual  experience by examining our ability to visually discriminate between the  objects we see. There is a link between this ability and visual  phenomenal character, as demonstrated by our practice of diagnosing  visual impairments by testing visual discrimination. This  discrimination-based account will end up showing that high-level  features do not figure in visual experience after all, because  high-level features co-occur with arrangements of low-level features,  and so cannot be independently used to visually discriminate between  objects. Admitting high-level features would involve an unwelcome  revision to how we conceive of visual ability and visual impairment.