At the neurological level, behavior can be inferred based on hormone concentration, which in turn are influenced by hormone-release patterns; the numbers and locations of hormone receptors; and the efficiency of hormone receptors for those involved in gene transcription. Hormone concentration does not incite behavior, as that would undermine other external stimuli; however, it influences the system by increasing the probability of a certain event to occur.
Not only can hormones influence behavior, but also behavior and the environment can influence hormone concentration. Thus, a feedback loop is formed, meaning behavior can affect hormone concentration, which in turn can affect behavior, which in turn can affect hormone concentration, and so on. For example, hormone-behavior feedback loops are essential in providing constancy to episodic hormone secretion, as the behaviors affected by episodically secreted hormones directly prevent the continuous release of said hormones.
Three broad stages of reasoning may be used to determine if a specific hormone-behavior interaction is present within a system:
* The frequency of occurrence of a hormonally dependent behavior should correspond to that of its hormonal source.
* A hormonally dependent behavior is not expected if the hormonal source (or its types of action) is non-existent.
* The reintroduction of a missing behaviorally dependent hormonal source (or its types of action) is expected to bring back the absent behavior.