Investiture and Sentience

[+TheAlmighty]

Sorry if this has been posted before. Nightblood was given sentience by having steel invested with 1000 Breaths. Kandra are given sentience with two hemalurgic spikes. In Shadows of Self Paalm was able to maintain her sentience with only one spike, or a spike of an unknown substance. I'm doing a reread of Shadows and don't remember exactly how Paalm was doing it. Do you think Brandon has a chart for conversion of different forms of Investiture? It sounds like hemalurgy is able to steal vast amounts of it, if 1000 Breaths doesn't seem equal to 2 spikes. Does the new metal unknown to Harmony hold more Investiture than the other known metals? 

[kenod]

The reason for this difference is because the Kandra were already sentient (kind of) but had a block between the physical and the cognitive realm. The Spikes fixed that for them. Nightblood's sentience is because a large enough amount of Investure will naturally gain sentience (the same thing happens with spren on Roshar).

[Dunkum]

to add on, Paalm was also never fully right in the head, so to speak.  she has some sentience, but isn't really at the level of a full kandra.