Human interaction relies on an intricate, continuous stream of expressive signals that broadcast motivational, psychological, and physiological states to the external world. Affect display represents this communicative bedrock, encompassing the involuntary, reflexive expressions and culturally mediated bodily signals that convey an individual’s immediate emotional valence and arousal. Understanding how affect displays function, how they are neurologically generated, and how they are interpreted provides crucial insights across clinical psychiatry, social neuroscience, developmental psychology, and artificial intelligence.
Affect Display
1. Concise Definition
An affect display refers to the observable outward manifestation of an internal emotional or affective state communicated via facial expressions, vocal prosody, body posture, gestures, and autonomic somatic responses. In psychiatric diagnostic terminology, affect display denotes the dynamic, moment-to-moment behavioral presentation of emotion observed by an examiner during a clinical evaluation, contrasting sharply with the more sustained and pervasive subjective emotional state classified as mood.
Within the traditions of nonverbal communication theory and kinesics, established by scholars such as Paul Ekman and Wallace V. Friesen, an affect display constitutes a specific class of nonverbal behavior whose primary informational payload is the revelation of affective experience. Unlike instrumental actions designed to manipulate physical objects, affect displays are fundamentally semiotic, operating along an evolutionary continuum from automatic biological reflexes to consciously regulated, culturally conditioned socio-emotional presentations.
2. Etymology & Linguistic Origin
The term is a compound derived from two distinct linguistic roots. The word affect descends from the Latin affectus, meaning “a state of mind, disposition, mood, or mental condition,” which itself derives from the verb afficere (“to do something to, to act upon, to influence,” formed by the prefix ad- [toward] and facere [to do or make]). In nineteenth-century German psychology and psychoanalysis, this concept was articulated as Affekt, denoting an intensive, short-lived emotional surge accompanied by somatic excitation, which entered English psychological lexicons through translations of Wilhelm Wundt and Sigmund Freud.
The second constituent, display, originates from the Anglo-French despleier and Old French desploier (“to unfold, unfurl, exhibit, or spread out”), which in turn traces back to the Late Latin displicare (from dis- [apart, un-] and plicare [to fold]). When ethologists in the mid-twentieth century began describing stereotypical behavioral repertoires intended to broadcast signals among animals as “displays,” the two terms converged. Nonverbal communication researchers and clinical psychopathologists formally synthesized “affect display” in the 1960s to identify the explicit physical unfurling of internal feeling states.
3. Pronunciation & Grammatical Form
Pronunciation: In academic and clinical phonetics, the phrase is pronounced with the primary stress on the initial syllable of the psychological noun: /ˈæf.ɛkt dɪˈspleɪ/. It is essential to distinguish the noun form affect (stress on the first syllable, /ˈæf.ɛkt/) from the verb affect (stress on the second syllable, /əˈfɛkt/, meaning to produce an effect on).
Grammatical Form: Noun phrase (countable and uncountable). The plural form is affect displays. It typically serves as an objective or subjective nominative complement in psychiatric reports (e.g., “the patient exhibited a blunted affect display”) or as an operationalized independent or dependent variable in behavioral research (e.g., “measuring infant affect display during the Strange Situation protocol”). Related adjectival constructions include affective display, although “affect display” remains the predominant technical designator in both psychiatric diagnostic manuals and kinesic taxonomies.
4. Detailed Conceptual Explanation
At its core, an affect display is a multidimensional biological and behavioral event. When an organism encounters an emotionally provocative stimulus, whether an external environmental hazard or an internal mnemonic cascade, a constellation of neurochemical systems activates within the central and peripheral nervous systems. The limbic structures, particularly the amygdala, anterior insula, and periaqueductal gray, initiate immediate effector patterns via the cranial nerves and autonomic nervous system. These neurobiological signals simultaneously mobilize the somatic musculature of the face, alter laryngeal and respiratory mechanics to shape vocal prosody, and adjust skeletal musculature to configure gross bodily posturing.
The scope of affect display spans a critical continuum between spontaneous involuntary expression and deliberate, voluntary modulation. Spontaneous affect displays are regulated primarily through subcortical pathways, including the extrapyramidal tract, which governs the involuntary contractions of facial muscles (such as the genuine orbicularis oculi contraction characteristic of a Duchenne smile). Conversely, voluntary or regulated affect displays are governed by cortical pathways, notably the primary motor cortex and pyramidal tract, allowing individuals to feign, suppress, mask, or accentuate emotional outputs according to pragmatic demands or cultural etiquette.
To establish the boundaries of the concept, an affect display must be conceptually untangled from several related psychological constructs. It is not synonymous with the internal subjective feeling (the conscious phenomenological experience of being sad, angry, or joyful). An individual may experience intense subjective dread while maintaining a stoic, neutral affect display, a phenomenon frequently observed in individuals conditioned to mask vulnerability. Nor is an affect display identical to an emblem or an illustrator in kinesic classification. While an emblem represents an arbitrary, culturally coded symbolic gesture with a direct verbal translation (such as a thumbs-up or an OK sign), an affect display is anchored in phylogenetic emotional prototypes that preserve cross-species evolutionary functions.
Furthermore, in diagnostic psychiatric practice, affect display is bounded by temporality. While mood describes the sustained, pervasive emotional climate that colors an individual’s worldview across days, weeks, or months (akin to the climate of a geographical zone), affect display represents the observable emotional weather at a specific instant during interpersonal interaction. A patient with a chronic, severe major depressive disorder (depressive mood) may nevertheless exhibit a transient, congruent affect display of irritation or momentary amusement when challenged or provoked by a clinician.
5. Historical Development
The scientific conceptualization of affect displays originated with Charles Darwin’s landmark 1872 work, The Expression of the Emotions in Man and Animals. Darwin posited that emotional expressions are evolved, biologically grounded adaptations that originally served specific survival imperatives. For example, baring the canines in an aggressive display functioned as an offensive preparation for biting, while widening the eyes in fear maximized the visual field to locate escape trajectories. Darwin demonstrated that these displays are largely universal across human populations and share explicit homologies with non-human primates.
During the mid-twentieth century, the ethological revolution led by Konrad Lorenz and Nikolaas Tinbergen expanded upon Darwinian insight by investigating “display behavior” across evolutionary biology. Concurrently, within developmental psychology, Silvan Tomkins advanced his seminal affect theory in the early 1960s, arguing that human affect is governed by primary, discrete affect programs hardwired into the central nervous system. Tomkins identified nine innate affects (such as interest-excitement, enjoyment-joy, fear-terror, and distress-anguish), each indexed by explicit facial and physiological configurations.
Building directly upon Tomkins’s framework, Paul Ekman and Wallace V. Friesen published their groundbreaking 1969 paper, “The Repertoire of Nonverbal Behavior: Categories, Origins, Usage, and Coding.” In this seminal work, they formally classified nonverbal human behavior into five discrete categories: emblems, illustrators, regulators, adaptors, and affect displays. Ekman and Friesen’s subsequent field research in the highlands of Papua New Guinea provided empirical evidence that isolated populations, free from exposure to Western media, reliably identified and produced congruent facial affect displays for basic emotions such as anger, fear, disgust, sadness, surprise, and happiness.
In parallel, twentieth-century psychiatric medicine assimilated the term into the standardized Mental Status Examination (MSE). Through the codification of diagnostic criteria across revisions of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM) and the World Health Organization’s International Classification of Diseases (ICD), the assessment of affective display became an indispensable clinical metric for characterizing disorders including schizophrenia, major mood disorders, and borderline personality pathology.
6. Theoretical Foundations
The academic study of affect displays is characterized by long-standing theoretical tension between two dominant frameworks: the Basic Emotion Theory (BET) paradigm and the Theory of Constructed Emotion (TCE).
The Basic Emotion Theory paradigm, championed by Ekman, Carroll Izard, and their contemporaries, posits that a limited set of biologically universal basic emotions (such as anger, fear, sadness, disgust, surprise, and joy) correspond to evolved, dedicated neurobiological “affect programs.” Under this model, an activated affect program generates a synchronized, modular output cascade across physiological arousal, subjective experience, and an involuntary facial and bodily affect display. Although BET acknowledges that “display rules” learned through social conditioning can subsequently inhibit, mask, or exaggerate these outputs, the canonical physical presentation is viewed as an innate, biologically determined fingerprint of the underlying emotion.
In contrast, the social-functionalist and constructivist schools of thought, articulated by researchers such as James Russell and Lisa Feldman Barrett, propose that emotional categories do not possess dedicated subcortical neural modules or invariant motor readouts. Instead, the constructivist framework suggests that an affect display is the emergent product of more fundamental neurobiological dimensions: core affect (characterized by valence and physiological arousal) combined with conceptual categorization, situational appraisal, and language. Under this perspective, what observers code as an “angry affect display” is not an automated biological reflex, but a contextually situated behavioral configuration constructed by the brain to manage an ongoing environmental transaction.
A third theoretical foundation emerges from the Behavioral Ecology View pioneered by Alan Fridlund. Fridlund challenges the premise that affect displays are direct “readouts” of internal feeling states, arguing instead that displays evolved strictly as social communication tools designed to broadcast behavioral intentions to conspecifics. Under Fridlund’s behavioral ecology framework, a facial configuration that classic theory labels “sadness” functions primarily not as an emotional leakage of inner misery, but as an interactive recruitment signal intended to elicit caregiving or appease potential aggressors.
7. Key Components, Types & Dimensions
Affect displays can be systematically deconstructed across physiological modalities and clinical presentations:
- Facial Muscular Configurations: The most refined component of human affect display, coordinated by the seventh cranial nerve (facial nerve) acting on the mimetic facial muscles. These configurations are objectively classified using the Facial Action Coding System (FACS) into discrete Action Units (AUs), such as AU 4 (brow lowerer in distress or anger) or AU 12 (zygomaticus major puller in joyful displays).
- Vocal Prosody and Acoustic Markers: Acoustic variations in speech, including fundamental frequency (pitch), pitch variability, speech rate, intensity (volume), and spectral tilt. High-arousal affect displays, such as panic or rage, manifest in elevated pitch and acoustic energy, whereas depressive or flat affect displays exhibit prosodic monotonicity.
- Kinesic and Postural Alignment: Global skeletal orientations mediated by the musculoskeletal system. Expansive, open bodily posturing typifies dominant or joyful affect displays, while collapsed, slumped, closed postures communicate defeat, shame, or despair.
- Autonomic and Visceral Indicators: Observable somatic expressions driven by the sympathetic and parasympathetic branches of the autonomic nervous system. These include cutaneous flushing or blanching, pupillary dilation, diaphoresis, respiratory rate alterations, and lachrymation (crying).
In diagnostic and clinical psychiatry, affect display is qualitatively and quantitatively characterized across several standard clinical dimensions:
- Broad / Full Affect: A normative presentation characterized by a dynamic, flexible spectrum of emotional expression that shifts naturally in congruence with the conversational topic and environmental context.
- Restricted / Constricted Affect: A notable reduction in the range and intensity of emotional signaling; expressions are subdued, showing muted modulation during emotionally provocative prompts.
- Blunted Affect: A severe diminishment of affective expression where facial mobility, vocal dynamics, and expressive gestures are profoundly dampened.
- Flat Affect: The near-total absence of outward affective signaling; the face remains mask-like, vocal output is completely monotonic, and gestures are virtually nonexistent. Flat affect is a cardinal negative symptom of schizophrenia.
- Inappropriate / Incongruent Affect: A clear discordance between the observed affect display and the semantic content or situational context (e.g., laughing or smiling broadly while recounting a traumatic event).
- Labile Affect: Rapid, erratic, and unpredictable fluctuations in emotional expression that bear minimal relationship to external triggers, frequently observed in bipolar disorder, borderline personality disorder, and pseudobulbar affect.
8. Examples & Illustrative Cases
To grasp the conceptual real-world manifestations of affect displays, consider the following contrasting scenarios across clinical, developmental, and interpersonal domains:
Case Illustration 1: Schizophrenia and Flat Affect Display
A 24-year-old man presenting with chronic schizophrenia sits rigidly in a clinical examination room. When the psychiatrist inquires about a devastating house fire that destroyed all his possessions and resulted in the death of a beloved pet, the patient’s facial musculature exhibits zero visible movement. His eyes remain fixated on the wall; his voice maintains an unchanging, robotic cadence devoid of pitch inflection; and his hands remain immobile in his lap. Although the patient later endorses profound internal psychological distress when answering a standardized self-report scale, his physical affect display is classified as clinically flat. This divergence illustrates the profound dissociation that can occur between subjective feeling and objective affect display.
Case Illustration 2: Pseudobulbar Affect and Neurological Lability
A 68-year-old woman recovering from a bilateral stroke in the prefrontal-subcortical circuitry experiences uncontrollable episodes of explosive laughter while attending a solemn funeral service. The laughter erupts abruptly, complete with facial grimacing, lachrymation, and spasmodic respiratory vocalizations, despite the fact that she consciously feels profound sorrow and mortification regarding her behavior. This case illustrates a severe neurological disruption of voluntary inhibitory pathways, leading to an entirely involuntary, contextually incongruent, and mechanically triggered affect display characteristic of pseudobulbar affect.
Case Illustration 3: Social Display Rules in Intercultural Negotiation
During an intensive diplomatic negotiation between American and Japanese corporate executives, a contentious breakdown in contractual terms occurs. The American negotiator visibly displays an angry affect display: furrowed brows (AU 4), narrowed eyelid apertures, elevated vocal intensity, and rapid, aggressive gesticulation. Conversely, the Japanese negotiator, operating under collectivist cultural display rules that prioritize social harmony and emotional containment, responds with an affect display comprising a neutral facial expression accompanied by a polite, subtle smile and measured, tranquil vocal prosody. While both individuals experience comparable physiological sympathetic activation, their respective affect displays are shaped by vastly different learned cultural display scripts.
9. Measurement & Assessment
The quantification and assessment of affect displays vary by discipline, utilizing behavioral coding, psychophysiological instruments, and structured psychiatric interviews.
The gold standard for the objective measurement of facial affect display in behavioral science is the Facial Action Coding System (FACS), developed by Paul Ekman, Wallace V. Friesen, and Joseph C. Hager. FACS operates by decomposing all observable facial movements into discrete, anatomically based Action Units (AUs) tied to the contraction of individual facial muscles. Certified FACS coders analyze high-speed video footage frame-by-frame, scoring the presence, onset, apex, offset, and intensity (on a five-point scale from A to E) of each AU. For instance, a genuine display of happiness requires the simultaneous activation of AU 6 (cheek raiser, contracting the orbital portion of the orbicularis oculi) and AU 12 (lip corner puller, zygomaticus major), whereas a deceptive or forced smile typically exhibits AU 12 in the absence of AU 6.
In clinical psychiatric settings, affect display is evaluated via direct observation during the Mental Status Examination (MSE), augmented by standardized clinical rating scales. The Scale for the Assessment of Negative Symptoms (SANS), formulated by Nancy Andreasen, contains dedicated subscales to quantify affective flattening or blunting across five distinct parameters: unchanging facial expression, decreased spontaneous movements, paucity of expressive gestures, poor eye contact, and affective non-responsiveness or lack of vocal inflections. Similarly, the Positive and Negative Syndrome Scale (PANSS) features items specifically evaluating emotional withdrawal and blunted affect.
Technological innovations have introduced automated facial expression analysis driven by deep convolutional neural networks and computer vision algorithms. Systems such as OpenFace and commercial affective computing platforms map facial landmarks in three-dimensional space, providing real-time tracking of micro-expressions, head orientation, and eye gaze. Concurrently, voice acoustics software analyzes recordings to extract markers of vocal affect display, including jitter, shimmer, harmonics-to-noise ratio, and fundamental frequency contours.
10. Applications & Practical Significance
The study of affect display has wide-ranging implications across clinical medicine, technology, jurisprudence, and organizational leadership:
Clinical Medicine and Psychiatry: Objective evaluation of affect displays serves as an essential diagnostic, prognostic, and therapeutic index. Monitoring changes in affect display helps track therapeutic efficacy during pharmacological or psychotherapeutic interventions for major depression. In neurodevelopmental conditions such as autism spectrum disorder (ASD), atypical affect display and impaired decoding of others’ affective signals represent core diagnostic criteria that guide early behavioral interventions.
Affective Computing and Artificial Intelligence: As autonomous systems, social robotics, and human-computer interfaces become ubiquitous, engineers rely on psychological models of affect display to design emotionally intelligent systems. Companion robots in eldercare, for instance, utilize affective recognition models to detect signs of pain, distress, or confusion in patients, while synthesized conversational agents are programmed to generate congruent facial and vocal affect displays to build interpersonal rapport.
Forensic and Interrogative Psychology: In criminal justice and security environments, investigative personnel observe nonverbal affect displays to assess stress, detect deception, and monitor escalating aggression. Although researchers caution against oversimplified beliefs in infallible nonverbal “tells,” analyzing incongruencies between verbal narratives and dynamic micro-affect displays provides investigators with valuable behavioral hypotheses.
Organizational Dynamics and Emotional Labor: In occupational sociology and organizational behavior, the concept of affect display is central to the framework of “emotional labor,” coined by Arlie Hochschild. Employees in client-facing environments (such as healthcare, hospitality, and flight service) are contractually expected to perform specific affect displays—such as enthusiasm, warmth, or composed reassurance—regardless of their internal somatic states, often leading to psychological strain and occupational burnout.
11. Research & Empirical Evidence
Extensive empirical research spanning cross-cultural anthropology, social psychology, and cognitive neuroscience has mapped the parameters of affect display over the past half-century.
Paul Ekman’s seminal cross-cultural investigations in the late 1960s and 1970s, conducted in the United States, Japan, Chile, Argentina, and among the pre-literate Fore people of New Guinea, documented consistent cross-cultural recognition rates of facial affect displays for happiness, sadness, disgust, anger, fear, and surprise. Replications by David Matsumoto and colleagues across dozens of nations reinforced these findings, indicating that despite cultural variations in display rules, the primary morphological configurations of these basic affect displays are conserved across human societies.
Developmental psychology has illuminated the chronological trajectory of affect display acquisition. In the landmark Still Face Experiment conducted by Edward Tronick in 1978, mothers were instructed to suddenly adopt an entirely flat, non-responsive affect display while interacting with their infants. Within seconds of the mother suppressing her affect display, infants exhibited acute distress, actively vocalizing, pointing, and arching away, before collapsing into withdrawal and crying. This classic research established that infant affective and social development is fundamentally dependent on reciprocal, contingency-based maternal affect displays.
Neuroimaging and lesion studies have elucidated the neurological architecture underlying affect displays. Damage to the right cerebral hemisphere, particularly the right temporoparietal junction and right frontal operculum, frequently induces expressive aprosodia—a condition where patients lose the ability to generate emotional vocal affect displays despite intact linguistic competence. Functional magnetic resonance imaging (fMRI) studies led by neuroscientists such as Antonio Damasio demonstrate that viewing emotional affect displays in others reliably recruits human mirror neuron networks and limbic structures, providing an automatic neurological foundation for emotional empathy and social attunement.
12. Cultural & Cross-Cultural Considerations
While the anatomical capacity to execute specific affect displays is a biological human universal, the social deployment, contextual timing, and social interpretation of these displays are heavily moderated by cultural display rules.
In individualistic cultures, such as those found in North America and Western Europe, cultural display rules frequently encourage the explicit, overt expression of emotional affect displays, particularly high-arousal positive affects (such as exuberant joy). Authenticity is often conceptualized as aligning one’s outward affect display directly with one’s internal affective state. In contrast, in many collectivistic East Asian societies, which prioritize interpersonal harmony and hierarchy, social display rules frequently prescribe the dampening, suppression, or masking of disruptive high-arousal affect displays, including overt anger, pride, or deep sadness. In these contexts, smiling is often deployed as a strategic affect display to ease social tension, mask discomfort, or maintain relational cohesion rather than to signal personal amusement.
Furthermore, cultural differences influence how observers decode affect displays. Research led by Takahiko Masuda demonstrated that while Western observers assess an individual’s affective display in isolation, East Asian observers systematically incorporate the affective displays of surrounding group members into their evaluation of the target individual’s emotional state. Eye-tracking paradigms have revealed that Westerners predominantly fixate on the mouth region when decoding facial affect displays, whereas East Asian participants prioritize the eye region (the periocular Action Units), perceiving the eyes as less susceptible to intentional, deceitful motor control.
13. Criticisms, Debates & Limitations
Despite widespread clinical adoption and substantial empirical support, the construct of affect display remains an area of vigorous academic controversy.
The primary critique originates from constructivist researchers led by Lisa Feldman Barrett. In her paradigm-shifting evaluations of the nonverbal communication literature, Barrett argues that traditional basic emotion experiments suffered from severe methodological artifacts, such as relying on forced-choice response formats, using exaggerated theatrical caricatures instead of naturalistic facial movements, and providing contextual priming. Naturalistic behavioral recordings indicate that people display tremendous behavioral variability during emotional episodes: individuals frequently scowl when they are concentrating rather than angry, cry when they are ecstatic, and laugh when they are anxious or overwhelmed. Consequently, constructivists argue that treating specific facial configurations as direct readouts of universal internal states is scientifically fundamentally flawed.
Another major criticism concerns the uncritical reliance on automated emotion-recognition technology in commerce and law enforcement. Critics point out that proprietary computer vision algorithms routinely conflate facial muscle movement with subjective affective states, falsely assuming that a scowl equates to malicious intent or that a blunted affect display equates to untrustworthiness. The Association for Psychological Science (APS) issued a comprehensive consensus report highlighting that modern scientific evidence does not support the premise that an individual’s internal emotional state can be reliably inferred from a facial affect display in the absence of broad situational context.
14. Related Terms & Distinctions
Clarifying how affect display relates to similar psychiatric and psychological constructs prevents conceptual ambiguity:
- Affect Display vs. Mood: Mood is an enduring, sustained, diffuse subjective internal emotional state experienced over days to weeks (e.g., dysthymia or euthymia), whereas affect display is the immediate, observable, moment-to-moment behavioral manifestation of emotion observed during interpersonal transactions.
- Affect Display vs. Microexpression: A microexpression is an exceedingly brief (lasting roughly 1/25th to 1/5th of a second), involuntary facial affect display that leaks out when a person deliberately attempts to conceal or repress their true emotion. An affect display is a broader, overarching category that includes macro-expressions, postures, and vocal acoustics lasting from several seconds to continuous interactions.
- Affect Display vs. Emotional Labor: Emotional labor refers to the psychological process and effort required by an employee to regulate and display organizationally desired emotions. The affect display itself is the concrete, outward behavioral outcome (e.g., a welcoming smile or calm demeanor) generated through that internal labor.
- Flat Affect vs. Anhedonia: Flat affect is an observable deficiency in outward emotional expression, whereas anhedonia is the subjective neurological inability to experience pleasure from intrinsically rewarding stimuli. A patient may suffer from severe anhedonia while retaining a normal affect display, or exhibit completely flat affect while maintaining the internal capacity for hedonic enjoyment.
- Affect Display vs. Emblem: Emblems are symbolic, culturally agreed-upon nonverbal gestures that possess precise, dictionary-like verbal translations (such as a salute or peace sign), whereas affect displays are rooted in evolutionary affective responses and lack direct verbal syntax.
15. Summary / Key Takeaways
- An affect display is the outward behavioral manifestation of an emotional state, expressed through facial expressions, vocal prosody, kinesic postures, and autonomic indicators.
- In clinical psychiatry, affect display is a core component of the Mental Status Examination, evaluated alongside sustained mood to diagnose and monitor mood disorders, schizophrenia, and neurological injuries.
- Affect displays operate on a continuum from involuntary, subcortically generated biological reflexes to consciously managed, cortically regulated social communications.
- The Facial Action Coding System (FACS) provides an anatomically based framework to objectively measure facial affect displays via discrete Action Units.
- Cultural display rules dictate when, where, and to what degree affect displays are amplified, suppressed, or masked within specific social contexts.
- Contemporary affective science actively debates whether affect displays represent universal, biologically hardwired readouts (Basic Emotion Theory) or flexible, context-dependent behavioral adaptations (Constructivist Theory and Behavioral Ecology).
Ultimately, affect displays serve as a vital communicative interface connecting our internal physiological and psychological landscapes with the external social environment. Whether functioning as an involuntary biological reflex or as a finely tuned element of cultural performance, the observable display of affect remains central to human empathy, social cohesion, and clinical evaluation.
References
- Darwin, C. (1872). The Expression of the Emotions in Man and Animals. John Murray. https://en.wikipedia.org/wiki/The_Expression_of_the_Emotions_in_Man_and_Animals
- Ekman, P., & Friesen, W. V. (1969). The repertoire of nonverbal behavior: Categories, origins, usage, and coding. Semiotica, 1(1), 49–98. https://en.wikipedia.org/wiki/Paul_Ekman
- Barrett, L. F. (2017). How Emotions Are Made: The Secret Life of the Brain. Houghton Mifflin Harcourt. https://en.wikipedia.org/wiki/Lisa_Feldman_Barrett
- Ekman, P., & Friesen, W. V. (1978). Facial Action Coding System: A Technique for the Measurement of Facial Movement. Consulting Psychologists Press. https://en.wikipedia.org/wiki/Facial_Action_Coding_System
- Tronick, E., Als, H., Adamson, L., Wise, S., & Brazelton, T. B. (1978). The infant’s response to entrapment between contradictory maternal emotional displays. Journal of the American Academy of Child Psychiatry, 17(1), 1–13. https://en.wikipedia.org/wiki/Edward_Tronick