ATPL - If a pilot has to perform two tasks requiring the allocation of cognitive resources:

Question id 483 - Human Performance and Limitations - ATPL - Airline Transport Pilot license

The only way of not seeing performance tail off is to switch to knowledge-based mode for the two tasks

A person reaches his limits as from simultaneous tasks, and performance will then tail off

The only way of not seeing performance tail off is to switch to rules-based mode for the two tasks

The sharing of resources causes performance on each task to be reduced