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Biological Theory of Emotions

For medical students2 min readUpdated 2026-10-10

The biological theory of emotions, developed by P.K. Anokhin, views emotional experiences as a crucial evolutionary tool for adaptation. This mechanism allows living organisms to instantly assess their internal metabolic needs and determine how successfully those needs are being met.

Main functionRapid assessment of internal needs and the success of their fulfillment.

Systemic mechanismAn emotion depends on the balance between the dominant need and the achieved result.

Reaction to harmInstant emotional assessment of damaging environmental factors.

Emotional stressDevelops during the prolonged inability to achieve the desired result.

Evolutionary Origin of Emotions

The emotional apparatus evolved as a reliable survival mechanism, present in all living creatures with an organized central nervous system. Although these experiences vary qualitatively across animals of different evolutionary levels, in humans they have reached maximum development, extending beyond biological activity into social behavior.

According to the first postulate of the theory, emotions serve as markers of metabolic needs:

Negative emotions. These occur when a need arises (hunger, thirst, fear). Subjectively, they are always unpleasant, forcing the organism to quickly recognize a deficit and triggering an active search for ways to eliminate it.
Positive emotions. These serve as an indicator that a need has been satisfied. This is the so-called sanctioning factor, which reinforces success. The organism does not need to conduct a detailed logical analysis of the situation—the pleasant sensation itself signals the completion of the search. Furthermore, the intensity of a positive experience directly depends on how difficult it was to overcome obstacles on the path to the goal.

Evaluative Function (The Third Postulate)

Emotions are necessary for the rapid evaluation of external stimuli to instantly determine whether they are beneficial or harmful. This speed is especially prominent when encountering tissue-damaging factors.

A classic clinical example is the formation of an antalgic (protective) posture during a knee joint injury. The patient does not waste time on a conscious "mathematical" calculation of the flexion angles that will minimize the load. The subjective feeling of pain forcefully compels them to adopt a position where discomfort subsides. Evolutionarily, this exact posture turns out to be the most favorable for subsequent recovery.

Mechanisms Within the Functional System

The emotional background accompanies all key stages of a behavioral act according to P.K. Anokhin: from afferent synthesis and decision-making to the formation of the action result acceptor and subsequent efferent synthesis. The valence of an emotion is determined by the ratio of the current dominant need to the actually achieved outcome.

Positive emotion. Develops when the adaptive result is achieved. It acts as a biological reward and confirms the correctness of the chosen behavioral strategy.
Negative emotion. Appears when the goal is not reached, meaning a mismatch of parameters occurs within the action result acceptor. This state is based on an enhanced orienting-investigatory reaction and prompts the subject either to overcome obstacles more stubbornly or to seek entirely new ways to achieve the goal.
Emotional stress. Arises as an extreme form of reaction when the organism is unable to fulfill its need and obtain the required result over a prolonged period.

Role of Learning and Memory

The process of emotional formation is inextricably linked to the subject's prior experience. Based on past attempts to satisfy basic biological or complex social needs, the action result acceptor is formed.

Memory of past successes and failures allows the goal to be emotionally colored in advance. In other words, emotional reactions are not purely innate automatisms; they largely depend on learning processes throughout life.

Mnemonic

An emotion is a scale: on one pan is the dominant need, on the other is the achieved result. Match — we get a sanctioning positive; mismatch — an orienting-investigatory negative.

Frequently asked questions

What is the action result acceptor in the theory of functional systems?

The action result acceptor is the apparatus for predicting and evaluating future results, the formation of which reflects goal-setting and higher motivation.

An ideal neural model of the intended result is created within this apparatus. The acceptor is based on the mechanisms of afferent synthesis and decision-making.

Main functions:

Compares predicted parameters with actually obtained results via feedback (reverse afferentation).
When the result matches the goal, a positive emotion arises (satisfaction).
When they do not match, a negative emotion is formed, which activates an orienting-investigatory reaction and a restructuring of the action program.

What consecutive stages make up a behavioral act according to Anokhin?

A behavioral act consists of four consecutive nodal stages:

Afferent synthesis — the first, initiatory stage of processing dominant motivation, memory, and afferentation.
Decision-making — sequentially replaces the previous stage, ensuring the choice of a specific goal and the formation of a dominant behavioral line via lateral inhibition.
Prediction of the required result (action result acceptor) — formation of the predictive apparatus and the neural model of the future result.
Efferent synthesis — the stage of central organization of executive action, uniting CNS structures. It culminates in the formation of a complex behavioral act.

What other theories of emotions are covered in normal physiology courses?

The normal physiology curriculum covers the following concepts:

Information theory of emotions (P.V. Simonov) — states that an emotion reflects the brain's evaluation of two factors: the actual need and the probability of its satisfaction.
Peripheral theory of emotions (James–Lange) — postulates that signals coming to the CNS from internal organs and somatic musculature play a decisive role in forming emotions. The emotion arises as a consequence of physiological changes rather than causing them, which is supported by the mechanism of reverse afferentation.

What is the sanctioning factor of behavior in Anokhin's theory?

It is a positive emotion that quickly confirms success in achieving a goal without complex analysis, serving as a signal to terminate search activity.

What is the biological role of negative emotions?

They are subjectively unpleasant and thereby reliably signal the presence of an unsatisfied metabolic need, stimulating the search for ways to satisfy it.

What happens when a mismatch occurs in the action result acceptor?

A negative emotion arises, based on an orienting-investigatory reaction. This forces a human or animal to seek new forms of behavior to overcome encountered obstacles.

Under what conditions does emotional stress develop?

Emotional stress forms in situations where the subject is deprived of the ability to achieve the required adaptive result for a prolonged period.

Go deeper

Nodal stages of the functional system (according to P.K. Anokhin)
Afferent and efferent synthesis
Action result acceptor and its formation
Orienting-investigatory reaction