The Deciders' analogue of psionic ability is called Decision. A decider's skill in Decision is determined by four variables, which the Deciders name Focus, Source, Outline and Balance. Focus and Source seem to be closely related to our "Control" and "Power" as the Deciders term them, i.e. Precision and Strength. Outline is a special Decision feature similar to, but not comparable to, our "Serendipity" or Fortune. Their fourth skill is Balance, which is measures the amount Coordination of their Decision skill. Humans do not naturally have Psionic Coordination, which makes it nearly impossible for us to maintain a balanced gestalt with the Deciders.
It is possible that our lack of coordination is the "noise" that interferes with their Focusing skill; I did not have the opportunity to pursue this question with the Deciders.
I believe that the Deciders have some sort of recipe for protecting their race from the Flames which involves building up strength in each of the four Decision skill areas. This suggests, and Katya agrees, that each of the three bloodlines of Hegemons the Omphalos Dust Worm bred to protect humanity has a particular psionic strength, Jayla (Red) representing precision, Katya (Green) representing strength, and Donella (Blue) standing for fortune. This seems to be borne out by the images in Cassandra's portrait of Katya.
If it is true that they know a procedure which provides defense against the Flames, I hope that we will be able to gain their trust sufficiently to learn what that procedure is.
The Deciders ability to generate the Focus necessary to stop the Flames was lost during a civil war. As a result, they experience interference from the human-inhabited planets in the dust nebula. The Tarn assault on Pierogi was the first battle in the campaign launched to silence this interference. To date, we have discovered no way to reduce the interference level of humans with psionic abilities. Interference is probably not dependent on place of birth, although the inhabitants with psionic powers in the Inworlds do not interfere with the Deciders' ability to stop the Flames.
I am hoping that Monsieur V'Dalari will be able to study some dust from the nebula to deduce whether it is in any way to blame for the interference.
The Deciders have also lost most of the Outline ability they need to stop the Flames. However, they claim that this is not needed for the protection part of their procedure. I assume that just as we need all three bloodlines, Outline is vital to some aspect of their procedure.
According to M. V'Dalari's research results, Deciders have difficulty improving their Focus and Outline abilities in the same way that Outworlders have difficulty improving Precision of Psi and Inworlders have difficulty improving Strength of Psi. Outline is the ability to pull together disparate things. Focus is the ability to concentrate psychically on one thing.
In the absence of Outline and Focus abilities the Deciders, with the aid of Ghier and some human assistants, have found a way to "reshape" their other abilities to cover the gaps left by Outline and Focus. (Picture two intersecting circles simulating a crosshatched pattern of four lines.)
Captain Thorssen has collected many of the facts which provoked my speculations in a file of her own.