## 2 Background and Related Work  
Modeling and quantifying emotions has always been a primary goal of psychology. Many theorists have tried to explain what emotions are. For the psychologist [PERSON], emotions are composed of \"physiological excitement, expressive behavior and conscious experience\" [25]. Another approach to the description of emotions is provided by [PERSON] and [PERSON] in their theory of emotion, which suggests that emotions occur as a result of physiological reactions to events. Thus, as we experience different events, our nervous system develops physical reactions to these events [26]. In this field of psychology, two perspectives are generally identified when defining a classification of emotions: discrete models and dimensional models. The discrete perspective presents that the basic elements of emotions are categorical or discrete entities. [PERSON] established the six basic emotions, which we experience in response to a stimulus: sadness, happiness, surprise, disgust, fear, and anger [9]. Dimensional models postulate that the basic building blocks or elements of emotions are dimensions such as arousal and valence. A first approach to dimensional models defined a three-dimensional model that includes three variables: pleasurable vs. unpleasant, arousing vs. subduing, and strain vs. relaxation [27]. Later, [PERSON] developed a model in which he considered emotions to be distributed in a two-dimensional circular space, where valence and arousal would be the coordinates used to determine an emotion [28]. While valence (pleasure) represents the horizontal axis, differentiating positively from negative emotions, the vertical axis, represented by arousal or activation, comprises the variation between active and passive emotional states. At the center of the circle, where intermediate values for valence and arousal happen, the neutral state of affection can be found. This model rose up to be one of the most popular models up to date. Following this line, [PERSON] joined [PERSON] to create a more detailed, three-dimensional model that could describe and measure emotional states using three numerical variables: Pleasure, Arousal, and Dominance [29]. Pleasure and Valence are indifferently interchanged, meaning that PAD and VAD refer to the same three dimensions of this model. While valence and arousal are key drivers when identifying emotions, dominance is often omitted, leading to Valence-Arousal models, such as the previously mentioned Circumplex Model. [PERSON] and [PERSON] also argued that the combination of the dimensions of arousal and valence, when combined, forms an appetitive and aversive emotional orientation, with arousal being a measure of intensity of said emotional orientation and valence the emotional direction, with pleasant being appetitive and unpleasant being aversive [30]. Regarding the development of dimensional models, over the years, a considerable number of resources built on these premises have emerged from psychological research laboratories for various languages. Numerous affect lexicons have been developed that collect values of valence, arousal, and dominance. [PERSON] and [PERSON] (1999) managed to develop the Affective Norms of English Words (ANEW) lexicon, using ratings from numerous annotators to achieve a list of more than 1000 words, becoming the lexicon par excellence for several years. It was not until 14 years later that [PERSON] et al. [18] extended this lexicon, using the same technique, to obtain a list of more than 13,000 words, in the well-known eXtended Affective Norms of English Words (XANEW). Likewise, lexicons have also been developed in different languages, such as in Spanish by [PERSON] et al. [31], or in German [PERSON] et al. [32]. Many are the studies that have dealt with the subject of classifying emotions, using data from Twitter. We can find some previous works, such as the study carried out by [PERSON] et al.