Perception (Recognition, Comprehension, Understanding)

• Segmentation
  How is the scene to be divided into regions or objects?
• Aggregation
  How are portions of the scene to be grouped together?
• Ambiguity
  How are ambiguous portions of the scene to be interpreted?
• Invariance and categories
  Each abstract category has many possible realizations in scenes. How are the invariants that characterize the category to be isolated?