Why is perception hard?
• Task: available signals → model of the world around
– signals are mostly accidental, inadequate
– sometimes disguised or falsified
– always mixed-up and ambiguous
• Reasoning about the source of signals:
– Integration of context: what do you expect?
– “Sensor fusion”: integration of vision, sound, smell etc.
– Source (and noise) separation:
   there’s more than one thing out there
– Variable perspective, source variation etc.
• depends on the type of signal
• depends on the type of object
• Much harder than chess or calculus!