reason

The EE concept of reason is the equivalent and substitute for the concept of rationality in standard economics, with "evolutionary rationality" as a bridging concept between both.
Reasonable behavior is rule-based decision-making and action, with the >rules being the outcome of long-run evolution of human action and individual learning, and not entirely of human design, to refer to Hayek's famous phrase. In comparison to standard calculatory choice, reason economizes on limited human attention, decision time and energy, and limited computational resources. The concept is therefore closely related to the idea of "bounded rationality". However, it is different in additionally emphasizing the human capability to commit decisions to rules unconditionally as an essential feature of human action in strategical contexts. That is, reason includes ways of decision-making which are not based on choices between a set of valued alternatives. Reason is a unity of rationality and >emotion.

In the analysis of reason, EE draws heavily on recent results of the brain sciences, so that the theory of reason can be based on empirical science, and not deductive logic alone.

Basic References

My understanding of human action and reason is strongly influenced by the classic:
Hayek, Friedrich August von, The Three Sources of Human Values, in: Law, Legislation and Liberty. A New Statement of the Liberal Principles of Justice and Political Economy. Volume 3: The Political Order of a Free People. Chicago: University of Chicago Press, 1979.

One of the greatest books ever written about the unity of sciences of human mind and brain, or biology and reason is:
Melvin Konner, The Tangled Wing. Biological Constraints on the Human Spirit. Second Edition. New York: Henry Holt, 2002.

One important source for EE in this field are evolutionary epistemology and evolutionary psychology. You find some resources here:
Evolutionary Epistemology
Evolutionary Psychology

Semantic Field
reason
cognition   actor   emotion