Emotional Intelligence (EI), often measured as an Emotional Intelligence Quotient (EQ), describes an ability, capacity, or skill to perceive, assess, and manage the emotions of one's self, of others, and of groups. As a relatively new area of psychological research, the definition of EI is constantly changing.
Origins of the concept
The distal roots of EI can be traced back to Darwin ’s (1872/ 1965) early work on the importance of emotional expression for survival and adaptation. In the 1900's, even though traditional definitions of intelligence emphasized cognitive aspects such as memory and problem-solving, several influential researchers in the intelligence field of study had begun to recognize the importance of the non-cognitive aspects. For instance, as early as 1920, E. L. Thorndike at Columbia University, used the term social intelligence to describe the skill of understanding and managing other people. 
Similarly, in 1940 David Wechsler described the influence of non-intellective factors on intelligent behavior, and further argued that our models of intelligence would not be complete until we can adequately describe these factors. In 1975, Howard Gardner's Frames of Mind: The Theory of Multiple Intelligences  introduced the idea of Multiple Intelligences which included both Interpersonal intelligence (the capacity to understand the intentions, motivations and desires of other people) and Intrapersonal intelligence (the capacity to understand oneself, to appreciate one's feelings, fears and motivations). In Gardner's view, traditional types intelligence, such as IQ, fail to fully explain cognitive ability . Thus, even though the names given to the concept varied, there was a common belief that traditional definitions of intelligence are lacking in ability to fully explain performance outcomes.
The first explicit application of the term "Emotional Intelligence" is mostly attributed to Wayne Payne's doctoral thesis, A study of emotion: Developing emotional intelligence from 1985 . Payne, however, did not publish his theory, so the article published in 1990 by Peter Salovey and John D. Mayer (1990) is generally regarded as the first systematic theoretical account of the construct. 
As a result of the growing acknowledgement of professionals for the importance and relevance of emotions to work outcomes , the research on the topic continued to gain momentum, but it wasn’t until the publication of Daniel Goleman's best seller Emotional Intelligence: Why It Can Matter More Than IQ that the term became widely popularized. . Nancy Gibbs' 1995 Time magazine article highlighted Goleman's book and was the first in a string of mainstream media interest in EI . Thereafter, articles on EI began to appear with increasing frequency across a wide range of academic and popular outlets.
Defining emotional intelligence
There are a lot of arguments about the definition of EI, arguments that regard both terminology and operationalizations. The first published attempt toward a definition was made by Salovey and Mayer (1990) who defined EI as “the ability to monitor one's own and others' feelings and emotions, to discriminate among them and to use this information to guide one's thinking and actions” 
Despite this early definition, there has been confusion regarding the exact meaning of this construct. The definitions are so varied, and the field is growing so rapidly, that researchers are constantly amending even their own definitions of the construct. . Up to the present day, there are three main models of EI:
The ability - based model
Mayer and Salovey's conception of EI strives to define EI within the confines of the standard criteria for a new intelligence. Following their continuing research, their initial definition of EI was revised to: "The ability to perceive emotion, integrate emotion to facilitate thought, understand emotions, and to regulate emotions to promote personal growth" .
The ability based model views emotions as useful sources of information that help one to make sense of and navigate the social environment . The model proposes that individuals vary in their ability to process information of an emotional nature and in their ability to relate emotional processing to a wider cognition. This ability is seen to manifest itself in certain adaptive behaviors. The model proposes that EI includes 4 types of abilities: 
- Perceiving emotions - the ability to detect and decipher emotions in faces, pictures, voices, and cultural artifacts- including the ability to identify one’s own emotions. Perceiving emotions represents a basic aspect of emotional intelligence, as it makes all other processing of emotional information possible.
- Using emotions - the ability to harness emotions to facilitate various cognitive activities, such as thinking and problem solving. The emotionally intelligent person can capitalize fully upon his or her changing moods in order to best fit the task at hand.
- Understanding emotions - the ability to comprehend emotion language and to appreciate complicated relationships among emotions. For example, understanding emotions encompasses the ability to be sensitive to slight variations between emotions, and the ability to recognize and describe how emotions evolve over time.
- Managing emotions - the ability to regulate emotions in both ourselves and in others. Therefore, the emotionally intelligent person can harness emotions, even negative ones, and manage them to achieve intended goals.
Measurement of the ability - based model
Different models of EI have led to the development of various instruments for the assessment of the construct. While some of these measures might overlap, most researchers agree that they tap slightly different constructs. The current measure of Mayer and Salovey’s model of EI, the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT) involves a series of emotion-based problem solving items. Consistent with the model's notion of EI as a type of intelligence, the test is modeled off of ability-based IQ tests. By testing a person’s abilities on each of the four branches of emotional intelligence, it generates scores for each of the branches as well as a total score.
Central to the four-branch model is the idea that EI requires attunement to social norms. Therefore, the MSCEIT is scored in a consensus fashion, with higher scores indicating higher overlap between an individual’s answers and those provided by a world wide sample of thousands of respondents. The MSCEIT can also be expert scored, so that the amount of overlap is calculated between an individual’s answers and those provided by a group of 21 emotion researchers 
Although promoted as an ability test, the MSCEIT is most unlike standard IQ tests in that its items do not have objectively correct responses. Among other problems, the consensus scoring criterion means that it is impossible to create items (questions) that only a minority of respondents can solve, because, by definition, responses are deemed emotionally 'intelligent' only if the majority of the sample has endorsed them. This and other similar problems have led cognitive ability experts to dismiss ability EI as a genuine intelligence.
Mixed models of EI
The Emotional Competencies (Goleman) model
The EI model introduced by Daniel Goleman  focuses on EI as a wide array of competencies and skills that drive managerial performance, measured by multi-rater assessment and self-assessment (Bradberry and Greaves, 2005). In Working with Emotional Intelligence (1998), Goleman explored the function of EI on the job, and claimed EI to be the largest single predictor of success in the workplace, with more recent confirmation of these findings on a worldwide sample seen in Bradberry and Greaves, "The Emotional Intelligence Quick Book" (2005)..
Goleman's model outlines four main EI constructs: 
- Self-awareness - the ability to read one's emotions and recognize their impact while using gut feelings to guide decisions.
- Self-management - involves controlling one's emotions and impulses and adapting to changing circumstances.
- Social awareness - the ability to sense, understand, and react to other's emotions while comprehending social networks.
- Relationship management - the ability to inspire, influence, and develop others while managing conflict.
Goleman includes a set of emotional competencies within each construct of EI. Emotional competencies are not innate talents, but rather learned capabilities that must be worked on and developed to achieve outstanding performance. Goleman posits that individuals are born with a general emotional intelligence that determines their potential for learning emotional competencies.
Measurement of the Emotional Competencies (Goleman) model
Measurement tools based on Goleman’s model of emotional intelligence include the Emotional Competency Inventory (ECI) and the Emotional Intelligence Appraisal, which can be taken as a self-report or 360-degree assessment (Bradberry and Greaves, 2005) (EIA).
The Bar-On model of Emotional-Social Intelligence (ESI)
Psychologist Reuven Bar-On (2006) developed one of the first measures of EI that used the term "Emotion Quotient". He defines emotional intelligence as being concerned with effectively understanding oneself and others, relating well to people, and adapting to and coping with the immediate surroundings to be more successful in dealing with environmental demands . Bar-On posits that EI develops over time and that it can be improved through training, programming, and therapy . Bar-On hypothesizes that those individuals with higher than average E.Q.’s are in general more successful in meeting environmental demands and pressures. He also notes that a deficiency in EI can mean a lack of success and the existence of emotional problems. Problems in coping with one’s environment is thought, by Bar-On, to be especially common among those individuals lacking in the subscales of reality testing, problem solving, stress tolerance, and impulse control. In general, Bar-On considers emotional intelligence and cognitive intelligence to contribute equally to a person’s general intelligence, which then offers an indication of one’s potential to succeed in life 
Measurement of the ESI Model
The Bar-On Emotion Quotient Inventory (EQ-i), is a self-report measure of EI developed as a measure of emotionally and socially competent behavior that provides an estimate of one's emotional and social intelligence. The EQ-i is not meant to measure of personality traits or cognitive capacity, but rather to measure one’s ability to be successful in dealing with environmental demands and pressures . One hundred and thirty three items are used to obtain a Total EQ (Total Emotion Quotient) and to produce five composite scales corresponding to the 5 main components of the Bar-On model.The major problem with this model and test is that it claims to measure some kind of ability through self-report items.
The Trait EI model
Petrides and Furnham (2000a) proposed a conceptual distinction between the ability based model and a trait based model of EI. Trait EI (or ‘emotional self-efficacy’) refers to "a constellation of behavioral dispositions and self-perceptions concerning one’s ability to recognize, process, and utilize emotion-laden information". This definition of EI encompasses behavioral dispositions and self perceived abilities and is measured by self report, as opposed to the ability based model which refers to actual abilities as they express themselves in performance based measures. Trait EI should be investigated within a personality framework. 
This conceptualization of EI as a personality trait leads to a construct that lies outside the taxonomy of human cognitive ability. This is an important distinction in as much as it bears directly on the operationalization of the construct and the theories and hypotheses that are formulated about it .
Measurement of the Trait EI model
There are many self-report measures of EI, including the EQi, the Swinburne University Emotional Intelligence Test (SUEIT), the Six Seconds Emotional Intelligence Assessment (SEI), the Schutte Self-Report Emotional Intelligence Test (SSEIT), a test by Tett, Fox, and Wang (2005), and Trait Emotional Intelligence Questionnaire (TEIQue) which is open-access and is available in 15 languages.
The TEIQue provides an operationalization for Petrides and colleagues' model that conceptualizes EI in terms of personality . The test encompasses 15 subscales organized under four factors: Well-Being, Self-Control, Emotionality, and Sociability. The psychometric properties of the TEIQue were investigated in a recent study on a French-Speaking Population, where it was reported that TEIQue scores were globally normally distributed and reliable.
The researchers also found TEIQue scores were unrelated to nonverbal reasoning (Raven’s matrices), which they interpreted as support for the personality trait view of EI (as opposed to a form of intelligence). As expected, TEIQue scores were positively related to some personality dimensions (optimism, agreeableness, openness, conscientiousness) as well as inversely related to others(alexithymia, neuroticism); TEIQue scores were also found to be related to socially desirable responding.
Alexithymia and EI
Alexithymia from the Greek words λέξις and θυμός (literally "without words for emotions") is a term coined by Peter Sifneos in 1973  to describe people who appeared to have deficiencies in understanding, processing, or describing their emotions. Viewed as a spectrum between high and low EI, the alexithymia construct is strongly inversely related to EI, representing its lower range. The individual's level of alexithymia can be measured with self-scored questionnaires such as the Toronto Alexithymia Scale (TAS-20) or the Bermond-Vorst Alexithymia Questionnaire (BVAQ) or by observer rated measures such as the Observer Alexithymia Scale (OAS).
Criticism of the theoretical foundation of EI
EI is too broadly defined and the definitions are unstable
One of the arguments against the theoretical soundness of the concept pertains that the constant changing and broadening of its definition- which has come to encompass many unrelated elements - had redeemed it an unintelligible concept: 
"What is the common or integrating element in a concept that includes: introspection about emotions, Emotional expression, non-verbal communication with others, empathy, self-regulation, planning, creative thinking and the direction of attention? There is none." (Locke, 2005)
Other criticsmention that without some stabilization of the concepts and the measurement instruments, meta-analyses are difficult to implement , and the theory coherence is likely to be adversely impacted by this instability.
EI cannot be recognized as a form of intelligence
Goleman's early work has been criticized for assuming from the beginning that EI is a type of intelligence. Eysenck (2000) writes that Goleman's description of EI contains unsubstantiated assumptions about intelligence in general, and that it even runs contrary to what researchers have come to expect when studying types of intelligence:
"Goleman exemplifies more clearly than most the fundamental absurdity of the tendency to class almost any type of behaviour as an 'intelligence'. . . .If these five 'abilities' define 'emotional intelligence', we would expect some evidence that they are highly correlated; Goleman admits that they might be quite uncorrelated, and in any case if we cannot measure them, how do we know they are related? So the whole theory is built on quicksand; there is no sound scientific basis".
Similarly, Locke (2005)  claims that the concept of EI in itself is a misinterpretation of the intelligence construct, and he offers an alternative interpretation: it is not another form or type of intelligence, but intelligence (the ability to grasp abstractions) applied to a particular life domain: emotions. He suggests the concept should be re-labeled and referred to as a skill.
EI has no substantial predictive value
Landy (2005)  has claimed that the few incremental validity studies conducted on EI have demonstrated that it adds little or nothing to the explanation or prediction of some common outcomes (most notably academic and work success). Landy proposes that the reason some studies have found a small increase in predictive validity is in fact a methodological fallacy - incomplete consideration of alternative explanations:
"EI is compared and contrasted with a measure of abstract intelligence but not with a personality measure, or with a personality measure but not with a measure of academic intelligence.Landy (2005)"
In accordance with this suggestion, other researchers have raised concerns with the extent to which self-report EI measures correlate with established personality dimensions. Generally, self-report EI measures and personality measures have been said to converge because they both purport to measure traits, and because they are both measured in the self-report form . Specifically, there appear to be two dimensions of the Big Five that stand out as most related to self-report EI – neuroticism and extraversion. In particular, neuroticism has been said to relate to negative emotionality and anxiety. Intuitively, individuals scoring high on neuroticism are likely to score low on self-report EI measures. 
The interpretations of the correlations between self-report EI and personality have been varied and inconsistent. Some researchers have asserted that correlations in the .40 range constitute outright construct redundancy, while others have suggested that self-report EI is a personality trait in itself.
Criticism on measurement issues
Ability based measures are measuring conformity, not ability
One criticism of the works of Mayer and Salovey comes from a study by Roberts et.al. (2001) , which suggests that the EI, as measured by the MSCEIT, may only be measuring conformity. This argument is rooted in the MSCEIT's use of consensus-based assessment, and in the fact that scores on the MSCEIT are negatively distributed (meaning that its scores differentiate between people with low EI better than people with high EI).
Ability based measures are measuring knowledge (not actual ability)
Further criticism has been offered by Brody (2004), who claimed that unlike tests of cognitive ability, the MSCEIT "tests knowledge of emotions but not necessarily the ability to perform tasks that are related to the knowledge that is assessed". The main argument is that even though someone knows how he should behave in an emotionally laden situation, it doesn’t necessarily follow that he could actually carry out the reported behavior.
Self report measures are susceptible to faking good
More formally termed socially desirable responding (SDR), faking good is defined as a response pattern in which test-takers systematically represent themselves with an excessive positive bias (Paulhus, 2002). This bias has long been known to contaminate responses on personality inventories (Holtgraves, 2004; McFarland & Ryan, 2000; Peebles & Moore, 1998; Nichols & Greene, 1997; Zerbe & Paulhus, 1987), acting as a mediator of the relationships between self-report measures (Nichols & Greene, 1997; Ganster et al., 1983).
It has been suggested that responding in a desirable way is a response set, which is a situational and temporary response pattern (Pauls & Crost, 2004; Paulhus, 1991). This is contrasted with a response style, which is a more long-term trait-like quality. Considering the contexts some self-report EI inventories are used in (e.g., employment settings), the problems of response sets in high-stakes scenarios become clear (Paulhus & Reid, 2001).
There are a few methods to prevent socially desirable responding on behavior inventories. Some researchers believe it is necessary to warn test-takers not to fake good before taking a personality test (e.g., McFarland, 2003). Some inventories use validity scales in order to determine the likelihood or consistency of the responses across all items.
Claims for the predictive power of EI are too extreme
Landy  distinguishes between the 'commercial wing' and 'the academic wing' of the EI movement, basing this distinction on the alleged predictive power of EI as seen by the two currents. According to Landy, the former makes expansive claims on the applied value of EI, while the later is trying to warn users against these claims. As an example. Goleman (1998) asserts that "the most effective leaders are alike in one crucial way: they all have a high degree of what has come to be known as emotional intelligence. ...emotional intelligence is the sine qua non of leadership". In contrast, Mayer (1999) cautions "the popular literature’s implication—that highly emotionally intelligent people possess an unqualified advantage in life—appears overly enthusiastic at present and unsubstantiated by reasonable scientific standards."
Landy further reinforces this argument by reminding that the data that constitutes the basis for all these claims is unfortunately held in ‘proprietary databases' thus redeeming it unavailable to independent researchers for reanalysis, replication, or verification. Thus, the credibility of the findings cannot be substantiated in a scientific manner, unless those datasets are made public and available for independent analysis.
Corporate uses and misuses of EI testing
Whenever a new assessment tool is proposed for hiring practices, the concern rises that it might create unfair job discrimination. In the EI context, Goleman's (1995) and Salovey and Mayer's (1990) suggestions that EI is a key working skill are not widely enough accepted. Consequently, using EI scores as a standard for hiring employees might arbitrarily discriminate against individuals.
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