The first question is more general, and would be important for preparation to meet other intelligent races. For understanding human cognition, the second question is the important one. To try to avoid this danger, I try to explicitly discuss any assumption which I introduce and is not trivial. The group continually develops new areas of mental activity, and increases and changes the scope of existing areas of mental activity. The individuals of this group cooperate well enough that they reach far better results by cooperation, and cooperation is important in the success of the group.
Cooperation require efficient communication.
The individuals do not have a 'magical' way of communication, and hence require physical means of communication. This means that communication requires some effort and time. The medium that is used for communication is not the medium of the primary sensory input. There is a limit on the amount of medium-specific information that an individual can handle at the same time. For Question 1, this limit may be of any value.