Emotions

Theories of Emotion

Emotions drive our interaction with the environment, representing the intersection of cognitive, physiological, and behavioral systems. They are complex, instinctive feelings resulting from our ability to perceive the environment and alert us to necessary behavioral actions. External stimuli are potent activators of internal mechanisms that drive our thoughts and mood.

Variables Contributing to Emotion

There are three interrelated variables that contribute to emotion:

  • External stimuli
  • Physiological systems
  • Brain systems

Early Theories of Emotion

James-Lange Theory

The James-Lange Theory suggests that the experience of emotion arises after our body has perceived and physiologically responded to external stimuli.

  1. You see a spider.
  2. The autonomic nervous system responds.
  3. You perceive these differences in autonomic arousal as “fear.”

The James-Lange Theory relies on the idea of autonomic specificity: different patterns of physiological arousal (i.e., heart rate, respiration, blood pressure, etc.) are the basis for the experiences of the different emotions. This is a bottom-up theory.

Cannon-Bard Theory

The Cannon-Bard theory developed based on three challenges to the James-Lange theory:

  1. Autonomic responses to stimuli are too slow to generate the often instantaneous feelings evoked by these stimuli.
  2. Artificially manipulating these physiological changes—e.g., by injecting adrenaline in the absence of fear-inducing stimuli, or by pharmacologically blocking physiological responses to such stimuli—or preventing the brain’s ability to perceive these changes all failed to affect the expression of emotion.
  3. The body does not contain enough specialized nerves individually convey the varied physiological changes evoked by different stimuli to the brain.

The Cannon-Bard theory implies that the conscious feeling of emotion and the physiological response to the stimulus are generated simultaneously.

  1. You see a spider, which activates your thalamus.
  2. The thalamus activates cortical regions, making you feel fear.
  3. The thalamus activates subcortical regions, modulating autonomic arousal.

The Cannon-Bard theory is a top-down theory, because the brain is ultimately driving the experience of emotion.

Schachter-Singer Two-Factor Theory

The Schachter-Singer theory, also known as the two-factor theory, incorporates the main premises of the previous two theories. It posits that external stimuli elicit increased autonomic activity, but the brain plays an important role in interpreting the context in which those changes were elicited before assigning an emotion.

  1. You see a spider.
  2. This activates your autonomic nervous system.
  3. You’re in the woods, so your brain interprets these changes as fear, and you jump and run.

Example 2:

  1. You see a spider.
  2. This activates your autonomic nervous system.
  3. You’re at the aquarium and the spider is in an exhibit, so you instead feel surprised & entertained.
Evidence for the Schachter-Singer Theory
  1. Participants were injected with epinephrine and told there would or would not be an effect on their heart rate.
  2. Participants watched either a happy or angry actor.
  3. Participants who were warned about the change did not experience any emotion, while those who were not warned misattributed their heart rate to their current emotional context.

Importantly, the participants who were not warned about the effects experienced emotion that matched that of the actor they watched.

Physiological changes can intensify an emotional experience, but the cognitive appraisal of the context where these physiological changes took place has a direct impact on the type of emotion attributed to any given experience.

The Schachter-Singer theory posits that external stimuli are subjected to context-dependent cognitive appraisal that interacts cooperatively with the physiological processes elicited in our body that together result in the emotion we feel.

Appraisal Theories

Further appraisal-based theories followed, with the foundation that emotional reactions are not driven by the external stimuli we encounter, but rather how we subjectively interpret (==appraise) them relative to personal variables like our goals, culture, concerns re:our or others’ well-being, etc. (“namely how one is doing in the agenda of living”).

These evaluations vary across appraisal dimensions, including:

  • Expectedness: Is this event predictable based on the configuration of events?
  • Pleasantness: Is this circumstance one that will be positive and beneficial, or aversive and bad for me?
  • Goal-oriented: Is this situation congruent with my current goals, or is it a distraction?
  • Fairness: Is this circumstance fair and just, or dishonest & deceitful?
  • Control: Do I have control over the present circumstances?
  • Self-concept relevance: Will this event influence how I view myself?
Constructionist Theories

Another viewpoint is reflected in constructionist theories of emotion, which believe the memories representing our previous encounters play an important role in generating emotions.

Rather than passively combining stimuli in their given context, these theories assert a primary role of the brain in integrating this sensory input with past episodes saved in memory à better explain why different individuals may display different emotions to the exact same event.

Summary of Theories of Emotion

  • Emotion is a subjective mental state that is usually accompanied by distinctive cognition, behaviors, and physiological changes.
  • James-Lange Theory suggested that patterns of arousal direct our emotional experience (i.e., my heart’s racing, therefore I’m afraid).
    • à bottom-up theory that depends on autonomic specificity to a wide array of experiences.
  • Cannon-Bard Theory combined these ideas and said the brain experiences arousal and emotion simultaneously (i.e., my heart is racing and I’m scared!).
    • à top-down theory.
  • Schachter-Singer Two-Factor Theory suggests we first experience arousal and then make a cognitive appraisal (i.e., my heart is racing, I’m in a jungle with scary animals, I’m scared!).
  • This led to other appraisal-based theories, which generally suggest that our emotional reactions are driven by our subject experience of the world relative to a variety of appraisal domains.
  • In contrast, constructionist theories of emotion suggest that the brain takes a more active role in generating emotion by incorporating our past experiences.

The Core Emotions

We can infer the emotional state of others through body language and, in particular, facial expressions. These emotions are recognizable across cultures.

The 6 basic core emotions were first scientifically studied in the 1970s, and some theories since have disagreed on the number of core emotions (i.e., some theories include contempt or embarrassment).

The 6 core emotions are each associated with a specific pattern of elevations or reductions in bodily activity.

  • Anger increases blood flow to the hands and arms, perhaps preparing the person to fight.
  • Disgust triggers intense muscle activation in the face, perhaps inducing a gag reflex or restricting airflow into the nose to reduce exposure to the “disgusting” thing.

There are additional emotions associated with their own patterns of activity:

  • Anxiety
  • Love
  • Depression
  • Contempt
  • Pride
  • Shame
  • Envy

Core emotions are even recognizable across species!

The Core Emotions Interact

Robert Plutchik’s Wheel of Emotions sought to expand on the idea of core emotions by suggesting that the rich tapestry of feelings we experience results from the idea that emotions often do not exist in isolation but can combine together.

If you got an email that you were accepted into graduate school, you might feel some combination of joy and anticipation that together produce optimism.

Summary of Core Emotions

  • There appear to be a set of core emotions that are recognizable across cultures and maybe even across species
  • These generally include: anger, sadness, fear, surprise, happiness & disgust
  • Facial expressions allow us to identify emotions in others
  • Each core emotion is associated with a characteristic pattern of elevated/reduced activity of different bodily activities
  • The Wheel of Emotions further suggests that our actual experience of emotion is created through a combination of multiple core emotions triggered by a given event

Brain Circuitry of Emotion

The Papez Circuit

We first learned about the important of the Papez circuit regions after scientists removed large parts of the temporal lobe in monkeys, which included several of these regions & the projections connecting them.

The range of behavioral deficits associated with this are known as Kluver-Bucy syndrome, which was later observed in clinical patients who had bilateral temporal lobe surgery to alleviate severe epilepsy.

Emotion generation begins with the thalamus, which combines sensory information from the external environment (== exteroception) with information from our internal physiological systems (== interoception).

The thalamus sends this information to the hypothalamus and the amygdala.

Hypothalamus

The hypothalamus is important for coordinating our bodily and physiological response to the changing demands of our environment, in an attempt to maintain homeostasis. It governs three broad categories of emotion-related behaviors & their associated physiological changes:

  1. Appetitive responses (e.g., feeding)
  2. Agonistic behavior (e.g., self-defense)
  3. Reproductive mating behavior
Amygdala

The amygdala functions similarly to the hypothalamus, but it can also form associations between unattended or neutral stimuli and the important events that were more immediately rewarding or threatening.

For example, when you are hungry, your hypothalamus triggers feelings of hunger when you smell Panera walking into Stamp. The amygdala noticed that you always meet up with your friend after class Tuesdays to grab lunch, so now you feel hungry when you see your friend waiting outside the classroom (== associative learning!).

In particular, the amygdala is crucial for the emotion of fear. Early evidence came from studying a patient, SM, who had Urbach-Wiethe’s disease that is a rare disorder that causes gradual bilateral destruction of the amygdala.

SM couldn’t recognize facial expressions of fear in photographs, nor could she draw a scared face despite being a talented artist. She showed little emotional reaction when discussing traumatic life events and displayed no fear—but rather curiosity and even joy—when handling snakes and spiders (which she said she hated), going through a scary haunted house, or watching horror movie clips.

Similarly, lesioning the amygdala in monkeys abolishes fear.

Most species of monkey possess an innate fear of snakes, but amygdala lesioned monkeys will readily approach and interact with rubber snakes.

Researchers used optogenetic activation of the amygdala in mice to demonstrate its role in fear learning.

In traditional fear conditioning, a neutral tone is paired with a shock. After conditioning, the mouse will display fear behavior to the tone.

Researchers optogenetically activated auditory inputs to amygdala, followed by a shock. After conditioning, the mice displayed freezing behavior to stimulation of this circuit.

Insula

The insula is important for the cognitive appraisal and evaluation functions that are crucial for the generation of emotion.

It receives both interoceptive and exteroceptive input and also has bidirectional connections with other cortical regions including prefrontal cortex, ACC, and amygdala. Together, these connections allow insula to combine interoceptive/exteroceptive information with subjective feelings and personal reflections of these stimuli and ultimately express them as emotion.

A recent preprint found that activity of insula neurons correlates with a model that predicts subjective happiness as monkeys are playing a gambling game! This correlation was not shared by neurons in another relevant brain region, the PFC (Rust et al., 2025 (bioRxiv)).

Orbitofrontal Cortex (OFC)

Two important regions in the prefrontal cortex are the orbitofrontal cortex (OFC) and the anterior cingulate cortex (ACC).

OFC has two major roles in emotion, which it sends to insula to help out with the appraisal of new events:

  1. OFC uses exteroceptive inputs combined with information from regions like amygdala & hypothalamus to assign positive or negative emotional valence to stimuli.
  2. OFC receives information regarding planning and “if/then” scenarios, along with episodic memories of past experiences and outcomes. This allows it to contribute to personal appraisal of higher-order self-reflection and internal thought.
Anterior Cingulate Cortex (ACC)

ACC performs a variety of complex, high-level functions that ultimately support emotion regulation, where value is assigned to emotional feelings created by the initial appraisal process + the resulting behavioral outcome.

ACC has three major roles:

  1. ACC monitors internal physiology (e.g., heart rate), using input from OFC, amygdala & hippocampus to determine what level/intensity of physiological changes are necessary to respond to a new experience based on its value and the anticipated outcomes.
  2. ACC helps us develop the conceptual meaning of the bodily sensations we experience, so we feel either satisfied or displeased by the emotional feelings that arise in response to different settings (i.e., a pro athlete responding to pressure compared to how an amateur would respond if you put them in that situation).
  3. ACC also evaluates the effort required to produce any type of response and assigns a positive or negative valence based on whether the outcome is worth the necessary effort to achieve it.

Summary of Brain Circuitry of Emotion

  • The Papez circuit is a network of brain regions crucial for emotion.
  • Together, they take input from the external & internal environment and help to evaluate those cues to generate an emotional response.
  • Removal of these regions (i.e., the temporal lobe) results in a range of behavioral and emotional deficits known as Kluver-Bucy syndrome.
  • The thalamus combines sensory information from the external environment (== exteroception) with information from our internal physiological systems (== interoception) and sends that information to the hypothalamus & amygdala.
  • The hypothalamus coordinates our physiological and psychological responses to a changing environment, especially across three broad categories: appetitive responses, agonistic behaviors, and reproductive behavior.
  • The amygdala forms responses between neutral/unattended stimuli and important events that were immediately rewarding or threatening.
  • The amygdala is particularly important for fear & fear learning, which we learned through the emotions & behaviors of people with Urbach-Wiethe’s disease.
  • The insula is important for cognitive appraisal.
  • The OFC assigns a positive or negative valence to stimuli and helps with the internal thought and planning associated with “if/then” scenarios.
  • ACC is important for emotional regulation by monitoring internal physiology, assigning conceptual meaning to bodily sensations & evaluating the required effort to achieve something.