The Curious Incident of the Dog in the Night-time Lesson Plan

Christopher has trouble understanding the facial expressions Siobhan draws for him (besides 'happy' and 'sad') and is also confused by metaphorical language. What do facial expressions and metaphors have in common? Why can't Christopher understand these things? 

Facial expressions and metaphorical langauge both refer to something beyond themselves. Facial expressions are visual indicators of a wide spectrum of emotions, and metaphors use words to convey non-literal meanings. Both of these sign systems are indirect. Christopher understands direct, specific communication, but has difficulty with complex or nuanced expression. He understands the concept of...