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The means by which we distinguish one emotion from another is a hotly contested issue in emotion research and affective science. This page summarises some of the major theories and the evidence supporting them. The classification of emotions has mainly been researched from two fundamental viewpoints. The first viewpoint is that emotions are discrete and fundamentally different constructs while the second viewpoint asserts that emotions can be characterized on a dimensional basis in groupings.
Emotions as discrete categories 
Many theorists define some emotions as basic where others are complex. Basic emotions are claimed to be biologically fixed and therefore universal to all humans and many animals as well. Complex emotions are then either refined versions of basic emotions, culturally specific or idiosyncratic. A major issue is to define which emotions are basic and which are complex.
One of the problems here is that there is no consensus on the method by which basic emotions can be determined. Theorists and researchers can point to universals in recognizing facial expressions (e.g. Ekman), distinctive physiological symptoms (e.g. the blush of embarrassment), or labels common to different languages. Moreover there should be some plausible developmental story concerning how the various non-basic emotions can be grounded in the basic ones.
- The Li Chi: Joy, anger, sadness, fear, love, disliking and liking (1st Century BC Chinese encyclopedia, cited in Russell 1991: 426).
- The Stoics: Pleasure/delight, distress, appetite and fear (Cicero, Tusculan Disputations, iv: 14-15).
- René Descartes: Wonder, love, hatred, desire, joy and sadness (Passions, 353).
- Baruch Spinoza: Pleasure, pain and desire (Ethics, pt. III, prop. 59).
- Thomas Hobbes: Appetite, desire, love, aversion, hate, joy and grief (Leviathan, pt. I, ch. 6).
- Silvan Tomkins: Enjoyment/Joy, Interest/Excitement, Surprise/Startle, Anger/Rage, Contempt/Disgust, Distress/Anguish, Fear/Terror, Shame/Humiliation.
- Paul Ekman (1972): Anger, disgust, fear, happiness, sadness and surprise.
- Paul Ekman (1999): Amusement, anger, contempt, contentment, disgust, embarrassment, excitement, fear, guilt, happiness, pride in achievement, relief, sadness/distress, satisfaction, sensory pleasure, shame, and surprise.
- Jesse Prinz (2004): Frustration, panic, anxiety, physical disgust, separation distress, aversive self-consciousness, satisfaction, stimulation, and attachment.
Basicality Debate 
Humans' subjective experience is often that emotions are clearly recognizable in ourselves and others. This apparent ease of recognition has led to the identification of a number of emotions that are said to be basic, and universal among all people. However, a recent debate among experts in the field has questioned this understanding of what emotions are. There has been recent discussion of the progression on the different views of emotion over the years.
On "basic emotion" accounts, activation of an emotion, such as anger, sadness, or fear, is "triggered" by the brain's appraisal of a stimulus or event with respect to the perceiver's goals or survival. In particular, the function, expression, and meaning of different emotions are hypothesized to be biologically distinct from one another. A theme common to many basic emotions theories is that there should be functional signatures that distinguish different emotions: we should be able to tell what emotion a person is feeling by looking at his or her brain activity and/or physiology. Furthermore, knowledge of what the person is seeing or the larger context of the eliciting event should not be necessary to deduce what the person is feeling from observing the biological signatures.
On "constructionist" accounts, the emotion a person feels in response to a stimulus or event is "constructed" from more elemental biological and psychological ingredients. Two hypothesized ingredients are "core affect" (characterized by, e.g., hedonic valence and physiological arousal) and conceptual knowledge (such as the semantic meaning of the emotion labels themselves, e.g., the word "anger"). A theme common to many constructionist theories is that different emotions do not have specific locations in the nervous system or distinct physiological signatures, and that context is central to the emotion a person feels because of the accessibility of different concepts afforded by different contexts.
Emotions can also be classified according to those that can occur when the individual is alone and not thinking about others, and those that seem more essentially socially directed. Examples of proposed social emotions include jealousy, love, hatred, guilt and gratitude. A current work by Rechter, Levontin and Kluger from the Hebrew University is done classifying and grouping social emotions, while relating and distinguishing them from non-social, or general, emotions.
Dimensional models of emotion 
For both theoretical and practical reasons some researchers define emotions according to one or more dimensions. Wilhelm Max Wundt, the father of modern psychology, proposed in 1897 that emotions can be described by three dimensions: "pleasurable versus unpleasurable", "arousing or subduing" and "strain or relaxation". In 1954 Harold Schlosberg named three dimensions of emotion: "pleasantness–unpleasantness", "attention–rejection" and "level of activation".
Dimensional models of emotion attempt to conceptualize human emotions by defining where they lie in two or three dimensions. Almost all dimensional models incorporate valence and arousal or intensity dimensions. Dimensional models of emotion suggest that a common and interconnected neurophysiological system is responsible for all affective states. These models contrast theories of basic emotion, which propose that different emotions arise from separate neural systems. Several dimensional models of emotion have been developed, though there are just a few that remain as the dominant models currently accepted by most. The two-dimensional models that are most prominent are the circumplex model, the vector model, and the Positive Activation – Negative Activation (PANA) model.
Circumplex model 
The circumplex model of emotion was first developed by James Russell. This model suggests that emotions are distributed in a two-dimensional circular space, containing arousal and valence dimensions. Arousal represents the vertical axis and valence represents the horizontal axis, while the center of the circle represents a neutral valence and a medium level of arousal. In this model, emotional states can be represented at any level of valence and arousal, or at a neutral level of one or both of these factors. Circumplex models have been used most commonly to test stimuli of emotion words, emotional facial expressions, and affective states.
Russell and Lisa Feldman Barrett describe their modified circumplex model as representative of core affect, or the most elementary feelings that are not necessarily directed toward anything. Different prototypical emotional episodes, or clear emotions that are evoked or directed by specific objects, can be plotted on the circumplex, according to their levels of arousal and pleasure.
Vector model 
The vector model of emotion first appeared in 1992. This two-dimensional model consists of vectors that point in two directions, representing a "boomerang" shape. The model assumes that there is always an underlying arousal dimension, and that valence determines the direction in which a particular emotion lies. For example, a positive valence would shift the emotion up the top vector and a negative valence would shift the emotion down the bottom vector. In this model, high arousal states are differentiated by their valence, whereas low arousal states are more neutral and are represented near the meeting point of the vectors. Vector models have been most widely used in the testing of word and picture stimuli.
Positive activation – negative activation (PANA) model 
The positive activation – negative activation (PANA) or "consensual" model of emotion, originally created by Watson and Tellegan in 1985, suggests that positive affect and negative affect are two separate systems. Similar to the vector model, states of higher arousal tend to be defined by their valence, and states of lower arousal tend to be more neutral in terms of valence. In the PANA model, the vertical axis represents low to high positive affect and the horizontal axis represents low to high negative affect. The dimensions of valence and arousal lay at a 45-degree rotation over these axes.
Plutchik's model 
Robert Plutchik offers a three-dimensional model that is a hybrid of both basic-complex categories and dimensional theories. It arranges emotions in concentric circles where inner circles are more basic and outer circles more complex. Notably, outer circles are also formed by blending the inner circle emotions. Plutchik's model, as Russell's, emanates from a circumplex representation, where emotional words were plotted based on similarity. In computer science, Plutchik's model is often used, in different forms or versions, for tasks such as affective human-computer interaction or sentiment analysis.
PAD emotional state model 
The PAD emotional state model is a psychological model developed by Albert Mehrabian and James A. Russell to describe and measure emotional states. PAD uses three numerical dimensions to represent all emotions. The PAD dimensions are Pleasure, Arousal and Dominance.
The Pleasure-Displeasure Scale measures how pleasant an emotion may be. For instance both anger and fear are unpleasant emotions, and score high on the displeasure scale. However joy is a pleasant emotion.
The Arousal-Nonarousal Scale measures the intensity of the emotion. For instance while both anger and rage are unpleasant emotions, rage has a higher intensity or a higher arousal state. However boredom, which is also an unpleasant state, has a low arousal value.
The Dominance-Submissiveness Scale represents the controlling and dominant nature of the emotion. For instance while both fear and anger are unpleasant emotions, anger is a dominant emotion, while fear is a submissive emotion.
Lövheim cube of emotion 
In 2011, Lövheim proposed a direct relation between specific combinations of the levels of the signal substances dopamine, noradrenaline and serotonin and eight basic emotions. A three-dimensional model, the Lövheim cube of emotion, was presented where the signal substances forms the axes of a coordinate system, and the eight basic emotions according to Silvan Tomkins are placed in the eight corners. Anger is, according to the model, for example produced by the combination of low serotonin, high dopamine and high noradrenaline. Lövheim wrote that as neither the serotonin nor the dopamine axis is identical to the "pleasantness" dimension in earlier theories, the cube seems somewhat rotated when compared to these models.
Culturally specific emotions 
One of the barriers to establishing a taxonomy of the emotions is that different cultures do not always recognise the same emotions in their languages. In some cases, the expressive behaviours, judgements or appropriate reactions associated with an emotion term are different. Moreover, a number of cultures have terms for emotions that have no direct equivalent in the English language. This argument, mainly from the field of anthropology, goes against the notion that emotions are biologically given. Paul Ekman, Izard, and others argue that research showing that humans from many different cultures are able to recognize the emotions associated with certain facial expression is evidence for these being universal emotions. However, there are a number of emotion terms that have been deemed culturally specific:
- Amae (Japan): Feeling of dependency akin to what infants feel towards their mothers. Important for bonding individuals to each other and cherished institutions. (Prinz 2004: 131).
- Awumbuk (Baining of Papua New Guinea): Sadness, tiredness or boredom caused by the departure of visitors, friends or relatives, (Russell 1991: 432).
- Fago (Ifaluk): A combination of love, compassion and sadness, (Lutz 1988, cited in Prinz 2004: 147).
- Gezellig (the Netherlands): Similar meaning to English word 'cozy', but occurring in the presence of other people, (Harre, 1986, Doi, 1973 cited in Prinz 2004: 131). Very similar to the German word Gemütlich/Gesellig.
- Ijirashii (Japan): Arising when seeing someone praiseworthy overcome an obstacle, (Matsumoto 1994 cited in Prinz 2004: 140).
- Ker (Ifaluk): Pleasant surprise, (cited in Goldie 2000: 91).
- Liget (Ilongot people): Aroused by situations of grief but closely related to anger, can inspire headhunting expeditions, (Rosaldo 1980 cited in Prinz 147).
- Malu (Dusun Baguk, Malaysia): Overlapping of shame and embarrassment, can be elicited by being in the presence of a person of higher rank, (Fessler 1999 cited in Prinz 2004: 156)
- Nginyiwarrarringu (Pintupi Aborigines of the Western Australian Desert): A sudden fear that leads one to stand up to see what caused it, (Russell 1991: 431)
- Rus (Ifaluk): Unpleasant surprise, cited in Goldie 2000: 91).
- Saudade (Brazil, Portugal): It describes a deep emotional state of nostalgic longing for an absent something or someone that one loves.
- Schadenfreude (Germany): Feeling of joy triggered by perception of someone suffering.
- Song (Ifaluk people, Micronesia): Close to anger, or admonition, with moralistic overtones and no disposition to revenge. (Lutz 1988 cited in Prinz 2004: 147).
- Sram (Russia): Shame specifically focused on sexual indecency, originating in religious discourse—also used as a noun denoting pudenda, or to prefix a location name in which sexual activity occurs (such as a red light district)
Prinz 2004 also cites patriotism as an emotion specific to Western cultures.
Culturally specific phobias or emotion syndromes 
- Koro (Assam and South Chinese): An intense anxiety that penis, breasts or vulva may retract into the body, (Yap 1965, cited in Prinz 2004: 136).
- Latah (Malaysia): Affecting middle aged women, an exaggerated startle reflex, outbursts of profanity and disposition to repeat whatever they hear. Cf. Mali-Mali in Philippines, yuan in Burma, ikota in Siberia, jumping mania in French Canadians of Main (Simons 1996, cited in Prinz 2004: 136).
- Pa-leng (China): A morbid fear of the cold even in hot weather, associated with a yin-yang imbalance (too little yang), (Kleinman 1980, cited in Prinz 2004: 136).
- Pibloktoq (Greenland Intuits): A fear causing sufferers to scream, tear off their clothing, break things, eat feces before collapsing into seizures, followed by deep sleep and loss of memory of the incident, (Yap 1974 cited in Prinz 2004: 135). Cf. amok in Malaysia and phii bod in Thailand. (Simons and Hughes 1993 cited in Prinz 2004: 136).
- Wild pig syndrome (Gururumba, New Guinea): Said to be caused when bitten by the ghosts of their ancestors, this syndrome affects young men entering maturity who begin running wild, stealing and shooting arrows for a few days. Cure involves being held over a smoking fire (Averill 1980, Griffiths 1997, Newman 1965, cited in Prinz 2004: 136).
- Witiko/Windigo (Algonquian Indians): A fear that one has been transformed into a cannibalistic monster, (Trimble, Monson, Dinges & Medicine 1984, cited in Prinz 2004: 135).
- Ekman, P. (1972). Universals and Cultural Differences in Facial Expression of Emotion. In J. Cole ed. Nebraska Symposium on Motivation. Lincoln, Nebraska: University of Nebraska Press: 207-283.
- Ekman, P. (1992). "An argument for basic emotions". Cognition and Emotion 6 (3): 169–200. doi:10.1080/02699939208411068.
- Ekman, P. (1999). Basic Emotions. In T. Dalgleish and T. Power (Eds.) The Handbook of Cognition and Emotion Pp. 45–60. Sussex, U.K.: John Wiley & Sons, Ltd.
- Fontaine, J.; Scherer, KR; Roesch, EB; Ellsworth, PC (2007). "The world of emotions is not two-dimensional". Psychological Science 18 (12): 1050–1057. doi:10.1111/j.1467-9280.2007.02024.x. PMID 18031411.
- Freitas-Magalhães, A. (2009). Emotional expression: The brain and the face. Porto: University Fernando Pessoa Press.
- Prinz, J. (2004). Gut Reactions: A Perceptual theory of Emotions. Oxford: Oxford University Press. ISBN 9780195309362
- Dana Sugu & Amita Chaterjee. "Flashback: Reshuffling Emotions", International Journal on Humanistic Ideology, Vol. 3 No. 1, Spring-Summer 2010 
- Russell, J.A. (1979). "Affective space is bipolar". Journal of Personality and Social Psychology 37 (3): 345–356. doi:10.1037/0022-35188.8.131.525.
- Russell, J.A. (1991). "Culture and the categorization of emotions". Psychological Bulletin 110 (3): 426–50. doi:10.1037/0033-2909.110.3.426. PMID 1758918.
Notes and references 
- Jesse Prinz Gut Reactions: A Perceptual Theory of Emotion (Oxford: Oxford University Press, 2004): page 157.
- Gendron, Maria; Barrett, Lisa Feldman (October 2009). "Reconstructing the Past: A Century of Ideas About Emotion in Psychology". Emotion Review 1 (4): 316–339. doi:10.1177/1754073909338877.
- Ekman, Paul (1992). "An Argument for Basic Emotions". Cognition and Emotion 6 (3/4): 169–200.
- Barrett, Lisa Feldman (2006). "Solving the Emotion Paradox: Categorization and the Experience of Emotion". Personality and Social Psychology Review 10 (1): 20–46.
- W.M. Wundt, Outlines of Psychology. (1897). In: Classics in the history of psychology. http://psychclassics.asu.edu/index.htm, York University 2010, Toronto.
- Schlosberg, H. (1954). "Three dimensions of emotion". Psychological Review 61: 81–8.
- Posner, Jonathan; Russell, J.A. & Peterson, B. S. (2005). "The circumplex model of affect: An integrative approach to affective neuroscience, cognitive development, and psychopathology". Developmental and Psychopathology 17: 715–734.
- Rubin, D. C.; Talerico, J.M. (2009). "A comparison of dimensional models of emotion". Memory 17: 802–808.
- Russell, James (1980). "A circumplex model of affect". Journal of Personality and Social Psychology 39: 1161–1178.
- Remington, N. A.; Fabrigar, L. R., Visser, P. S. (2000). "Re-examining the circumplex model of affect". Journal of Personality and Social Psychology 79: 286–300.
- Russell, James; Feldman Barrett, Lisa (1999). "Core affect, prototypical emotional episodes, and other things called emotion: dissecting the elephant". Journal of Personality and Social Psychology 76: 805–819.
- Bradley, M. M.; Greenwald, M. K., Petry, M.C., Lang, P. J. (1992). "Remembering pictures: Pleasure and arousal in memory". Journal of Experimental Psychology: Learning, Memory, & Cognition 18: 379–390.
- Watson, D.; Tellegan, A. (1985). "Toward a consensual structure of mood.". Psychological Bulletin 98: 219–235.
- Plutchik, R. "The Nature of Emotions". American Scientist. Retrieved 14 April 2011.
- Erik Cambria; Andrew Livingstone and Amir Hussain (2012). "The Hourglass of Emotions". Cognitive Behavioural Systems. Springer. doi:10.1007/978-3-642-34584-5_11.
- Mehrabian, Albert (1980). Basic dimensions for a general psychological theory. pp. 39–53. ISBN 0-89946-004-6.
- Bales, Robert Freed (2001). Social interaction systems: theory and measurement. pp. 139–140. ISBN 0-7658-0872-2.
- Lövheim H. A new three-dimensional model for emotions and monoamine neurotransmitters. Med Hypotheses (2011), Epub ahead of print. doi:10.1016/j.mehy.2011.11.016 PMID 22153577
- Shariff, A. F.; Tracy, J. L. (2011). "What Are Emotion Expressions For?". Current Directions in Psychological Science 20 (6): 395. doi:10.1177/0963721411424739.