The brain cannot handle all the information that comes through the senses. Initially, we're all fitted with much the same input-output processors; some may have faster memory access but this does not make up for inherent bandwidth limitations of the system. To reduce potential workload, distinctive processor restrictions have to be adopted; people become specialists in handling limited sets of data in limited ways. Thus, type is born.
Process control is structured in one of two ways. The first employs priority interrupts (open-loop with no feedback) so that input can be turned off while output is operating, or vice versa. An explorer (Ep) curbs rationalization so that information acquisition can be maximized. A planner (Ij) restricts data acquisition to increase rationalization capacity. However, being able to shut down an entire processing stream to give more resources to the other set of processes does pose obvious weaknesses regardless of how fast the switch can be made.
The second structure employs a comparator (with feedback and filter) to limit processing so that input and output can be kept online simultaneously. This closed-loop configuration considers only information that falls within narrow ranges, exploits rationalizations of others, and demands immediate closure in order to move on to the next step. Now, an observer (Ip) is dominated by input processes, whereas a leader (Ej) has rationalization in control. Stability (ego?) requires that, regardless of structure, only one process can be in ultimate control – input or output.
In a limited bandwidth scenario, processing has to rob Peter to pay Paul. Since all input and output have relative and absolute components, processing limits itself to a reduced set of preferences (N versus S and F versus T). The unused information and processes are still available if it weren't for the fact that stuff that's not regularly used tends to atrophy; and, we simply cannot be all things to all processes. Processing power is finite regardless of how it's employed so we are doomed to our limitations - right from the get-go. Instead of focusing on what we're not and trying to repair what's not broken, we need to better use what we've got.