The pursuit of truth is woven into the interstices of every organism. Any estimate of how best to survive and thrive in the reality in which we are immersed requires a sense of self, of the world, and of their relationship to each other.  I wish to explore the idea that this pursuit has at its heart two complementary modes of neurobehavioral reality testing: The correspondence of experience with the world and the coherence of the experience with previous experiences: “is it real” and “does it fit?”  At multiple levels of the nervous system, confidence in the validity of experience depends on these two processes.  A belief derived is “true” to the extent that it satisfies these tests and engenders confidence in effectiveness of behavior based on the belief.

The biological significance of “truth” and "belief" will be explored from the integrative perspective of ethology.  That is, the lenses of developmental biology, ecology, evolutionary biology, and physiology will be focused on the process of extracting meaning from our experiences in the world.

Two complementary cerebral processes ordinarily work in lockstep to provide us with more-or-less confidence as well as the strength of ensuing beliefs:  These processes involve an estimation of the validity of correspondence and coherence. Such estimations of validity guides the continuing reconciling of intentions, expectations, and actions at every level of the nervous system, invoking energetically more expensive higher levels only when lower levels are inadequate. A third area appears to evoke an emotional response to a perceived truth.  This site may be responsible for “hypergnosia,” an overwhelming and sometimes ecstatic sense of truth.

Correspondence” involves “reality-testing” of a percept, the cerebral representation of an experience in the world.  “Coherence” involves “theorizing,” that is, reality-testing of a percept by how well it relates to previous and ongoing parallel and collateral experiences.  As organisms develop, the “reference base” of previous experiences is enlarged and refined.  A valid correspondence is consonant with a theory; a valid theory is corroborated by correspondences.  In large measure, these consilient processes are lateralized in different hemispheres of the brain.  Ordinarily, these processes are more-or-less balanced, but asymmetry in neuro-activation in concert with our gifts for resolving cognitive dissonance and making virtues of necessities, can undermine our effectiveness in the real world.