A cognitive psychologist or a neuroscientist specializing in the study of sleep and its effects on learning, memory, and cognitive function.
The pervasive monotony of my commute provides ample opportunity for reflection on recent studies regarding the intricate interplay between sleep cycles and memory consolidation; particularly fascinating is the emerging evidence suggesting that sleep spindles may play a crucial role in transferring newly acquired information from short-term to long-term memory storage.  It's quite thought-provoking, really.