Alright, I know that I'm completely new here, but I really love your theories about spren. However, there was something I noticed about Syl, and the spren that get measured and defined in interlude 8.
Syl still acts mostly like she's unaware of changes to her life, up UNTIL Kaladin asks for her name on p110:
From here on, Syl begins to notice that she's acting differently from the other spren. She begins to realize her purpose in the grand scheme of things.
Now, when Ashir and Geranid start defining spren in I-8, they're doing essentially the same thing. In fact, this might almost be a secondary investiture. By cognitively attributing something to the spren that was not attributed to it before, they define it, and this changes the cognitive environment for that spren, and gives them a cognitive definition. Perhaps if you wrote down a name for a spren (like the Protector, who I suspect has become what it is because of its name - it reminds me of the face in the high storms, who might be Tanavast? Or at least some sort of protector for humanity on Roshar, or a protector for all of humankind against Odium) then it would begin to gain sentience from whoever was defining it. Since spren are so common place, people probably rarely name a spren, and if they do, it's only to define it's cognitive association.
So that was a bit rambling. Tell me what you think. I'm not sure on most of these points, but they seem to be making some sort of sense
Edit: OH wow, didn't realize this - maybe the reason why the Protector is even capable of draining their souls is because someone named it the Protector? Thus it takes into account all the people it is meant to protect, and takes a small part of their soul as part of the symbiotic relationship. Perhaps it used to be just a giant spren - maybe the only oceanspren (since there are riverspren), and the people of Kasitor named it when it appeared near their city.
(also part of the edit and completely off topic) Axies says "Blight it all"... which sounds like something from WoT, not tWoK. It would be hilarious if we started having WoT crossovers (which would also be terrible, but hey, one can always hope).
Second Edit: I keep on forgetting things I meant to address. What I'm wondering is if the Parshendi using infused gems in their beards makes them any different from the parshmen. It may be that by some form of magic they can use storm light to communicate with one another over long distances, which makes their songs possible (I'm pretty sure that one song is used to communicate battle strategies from one end of the battlefield to the other). And maybe there are a number of songs, or ways a song can be sung, each one corresponding to a different gemstone and thus a different attribute of those gemstones? I feel like this is something that should actually be addressed (and maybe has already been addressed) somewhere else...
