The Secret of Metaphor on Expressing Stronger Emotion (2022)

Abstract: Metaphors are proven to have stronger emotional impact than literal expressions. Although this conclusion is shown to be promising in benefiting various NLP applications, the reasons behind this phenomenon are not well studied. This paper conducts the first study in exploring how metaphors convey stronger emotion than their literal counterparts. We find that metaphors are generally more specific than literal expressions. The more specific property of metaphor can be one of the reasons for metaphors’ superiority in emotion expression. When we compare metaphors with literal expressions with the same specificity level, the gap of emotion expressing ability between both reduces significantly. In addition, we observe specificity is crucial in literal language as well, as literal language can express stronger emotion by making it more specific.

## introduction metaphors are widely used in human language, which allows people to communicate not just information, but also feelings and attitudes. it is generally believed that metaphors are especially effective in expressing subjective elements, such as sentiment and attitude. recent studies in psychology and computational linguistics thus provide a wide range of qualitative evidence which supports the idea that metaphors are closely related to sentiment. for example, @xcite use metaphorical expressions as a feature in sentiment polarity detection and find it can be an effective indicator. @xcite introduce a multitask framework which jointly optimizes a metaphor detection task and aspect-based sentiment analysis and observe considerable improvement on both tasks. more importantly, @xcite give the first quantitative finding which shows that 83.6% of annotated metaphors tend to * corresponding author have a stronger emotional impact than their literal counterparts. however, although researchers conduct fruitful studies showing how metaphors are closely related to sentiment, the reason behind this phenomenon is not well explored. investigating the mechanism of metaphor sentiment interaction can be quite promising. for instance, understanding how metaphor builds emotional bonds can guide metaphor generation models @xcite producing empathetic and persuading responses. the result can also be helpful for sentiment analysis, especially on metaphor-enriched text @xcite . in this paper, we introduce an exploratory answer to the question of how metaphors convey stronger emotion than literal language. to investigate this phenomenon, we manually analyse the metaphor-literal parallel corpus from moh dataset @xcite , see example in figure 1 ) where the more emotional expression is marked among each metaphor-literal pair. our study finds that metaphors might impose emotional impact on readers via giving more specific expressions, i.e., making the expression more precise. first, we find most metaphorical expressions are more specific than their literal counterparts. in other words, literal translations of metaphors usually convey more general meanings. it suits our intuition that metaphors are believed as more vivid. second, we find metaphor's stronger emotional impact is partially from its more specific description. when we compare metaphors and their literal counterparts where both share the same level of specificity, we find the superiority of metaphors in arousing emotional impact drops significantly. when we test the more-specific principle on literal expressions, we find more specific literal expressions do surpass general ones on emotional impact. we use linguistic relation hypernym and hyponym from wordnet @xcite to define the specificity in our analysis. specifically, hypernym denotes a word with a broad meaning yet hyponym denotes a word with a more specific meaning. so if a literal term is its metaphorical counterpart's direct hypernym, we know the metaphor describes a more specific meaning, or to say in a metaphorical way, draws a more precise picture. the figure 1 shows an example of the above situation: the synset of the literal expression misuses language is the direct hypernym of the metaphorical synset, which means the literal expression is more general and the metaphor is more specific. in case there is no direct hypernym or hyponym relation between metaphorical and literal expression, we compare the place of both in the wordnet hierarchy to determine which one is more specific. in figure 2 , we see clearly that from the top to the bottom in the wordnet hierarchy, expressions tend to be more specific. so we can determine the relative specificity of terms by comparing their relative position in the hierarchy. in summary, our contributions are mainly in two folds: 1) we introduce a novel hypernymhierarchy method to measure the specificity of language expression and find metaphors are usually more specific than literal counterparts; 2) we find the reason why metaphor express stronger term: rip sense/synset: synset('rip.v.04') sentences: the candidate ripped into his opponent mercilessly. literal: the candidate criticized his opponent mercilessly. emotion: the metaphorical expression is more emotional. ## experimental setup this study tests two research hypotheses: hypothesis 1: metaphors are generally more specific than their literal counterparts. in other words, metaphors are lower than their literal counterparts in the wordnet hierarchy. hypothesis 2: metaphors' stronger emotional impact is partially from metaphors' more specific expression. in other words, more precise expression is one of the reasons why metaphors convey stronger sentiment than their literal counterparts. to compare the specificity of metaphor and its literal counterpart, the hypernym-hierarchy information is assigned to both in parallel. to explore the role specificity plays in the interaction between emotion and metaphor, we first analyse the correlation between specificity and emotion label of metaphors. we then perform two more experiments to further test how specificity affects emotional impact: 1) labelling which one is more emotional between metaphor and literal counterpart with the same level of specificity; 2) labelling which one is more emotional between a more general literal expression and a more specific literal expression. the first test isolates the influence of specificity in the emotion comparison of metaphorliteral pair; the second tests whether specificity empowers literal expression to convey stronger sentiment.