I found Chapter 13's subject matter - based on how and why we perceive speech - to be particularly interesting. I have studied phonemes briefly in other psychology courses, but found the information provided as to how we associate different phonemes and how they are developed to be fascinating. It is nothing short of amazing to realize that the entire English language, through all of its complexity and depth, is essentially dependent of simply 47 different sounds. It truly puts things into perspective when you look at the smaller picture.
Another particularly intriguing aspect of the chapter is the study of Statistical Learning with infants. The fact that the infants - who obviously were not able to properly comprehend language - could still pick up on phonetic cues and transitional sounds is fascinating. This study alone says a lot about our natural capacity to interpret and actively use language in our lives, and, considering that all language is man made, definitely brings in questions of how we have evolved to better instinctively understand language.
I would love to see a similar test done for the infants (although obviously much more evolved and intuitive) with patients afflicted with either Broca's or Wernicke's Aphasia to see how their condition distorts or enhances how they interpret speech. While those with Wernicke's Aphasia would prove interesting just to see how they would reach certain conclusions while struggling with comprehension difficulties, I'd imagine that patients with Broca's Aphasia would actually be more skilled at discerning language fluidity than the average person, as their condition requires them to be more observant.