Identifying Metaphor Hierarchies in a Corpus Analysis of Finance Articles

Identifying Metaphor Hierarchies in a Corpus Analysis of Finance Articles Aaron Gerow (gerowa@tcd.ie) School of Computer Science & Statistics, Trinity College Dublin College Green, Dublin 2, Ireland Mark T. Keane (mark.keane@ucd.ie) School of Computer Science & Informatics, University College Dublin Belfield, Dublin 4, Ireland Abstract Using a corpus of over 17,000 financial news reports (involving over 10M words), we perform an analysis of the argument-distributions of the UP- and DOWN-verbs used to describe movements of indices, stocks, and shares. Using measures of the overlap in the argument distributions of these verbs and k-means clustering of their distributions, we advance evidence for the proposal that the metaphors referred to by these verbs are organised into hierarchical structures of superordinate and subordinate groups. Keywords: Metaphor; corpus analysis; word meaning; semantics; concept hierarchies; grounding. Introduction In recent years, significant progress has been made in deriving meaning from statistical analyses of distributions of words (e.g., Gerow & Keane, 2011a; Landauer & Dumais, 1997; Turney & Pantel, 2010; Michel et al., 2010). This distributional approach to meaning takes the view that words that occur in similar contexts tend to have similar meanings (cf. Wittgenstein, 1953) and that by analysing word usage we can get at their meanings. For example, the word co-occurrence statistics derived in Latent Semantic Analysis (LSA) seem to tell us about the structure of the lexicon, as they are good predictors of reaction times in lexical decision tasks (Landauer & Dumais, 1997). Simil- arly, word patterns drawn from WordNet, have been used to determine semantic relationships accurately enough to answer the multiple-choice analogy questions on the SAT college entrance test (Turney, 2006; Veale, 2004). More generally, it has been suggested that significant insights into human culture and behaviour can be derived from analysing very large corpora, like the Google Books repository (Michel et al., 2010). In this paper, we apply similar distri- butional analyses to understand the structure of metaphoric knowledge behind “UP and DOWN” verbs from a corpus of financial news reports. Lakoff (1992; Lakoff & Johnson, 1980) has argued that our understanding of many concepts – such as emotions and mental states – are grounded in a few ubiquitous metaphors. For example, spatial metaphors that structure emotional states, such as HAPPINESS IS UP and SADNESS IS DOWN, are found in nearly all languages. Similar spatial metaphors, of the sort we examine here, seem to ground many stock-market reports. Accounts of index, stock- market, and share movements tend to converge around metaphors of rising and falling, attack and retreat, gain and loss. These concepts appear to be grounded by core meta- phors that could be glossed as GOOD IS UP and BAD IS DOWN. Lakoff and Johnson (1980) have pointed to this UP-DOWN metaphor opposition as underlying accounts of wealth (WEALTH IS UP as in high class), the rise and fall of numbers (MORE IS UP / LESS IS DOWN) and changes in quantity (CHANGE IN QUANTITY IS WAR as in retreating profits and defensive trades). If such UP-DOWN metaphors ground the use of the words used in finance reports, a corpus analysis should be able reveal the structure of prominent concepts in the domain. Specifically, we analyse arguments taken by UP and DOWN verbs to determine whether there is evidence of hierarchical structuring in their grounding metaphors (see Gerow & Keane, 2011a, for a separate analysis of changes in this language over time). Figure 1: Venn Diagrams showing (a) rise covering most of soar and (b) rise covering soar and climb. Metaphor Hierarchies We propose that if one metaphor is more fundamental than another, it should play an organizing role in structuring other concepts; specifically, it might act as a superordinate, metaphoric concept that structures some set of basic-level, metaphoric concepts (Rosch et al., 1976). So, for example, the UP metaphor schema could be a superordinate to a set of more specific metaphors (like GAIN, GROW and so on). If this is the case, then the verb that best captures this funda- mental metaphor should have an argument-distribution that covers the argument-distributions of its subordinate meta- phors because, by definition, it is more general. Similarly, the verbs that refer to the basic-level metaphors – what we might call sibling metaphors – beneath this superordinate, should have smaller, more-equal overlaps in their argument- distributions. A corollary of this proposal is that if we compare the similarity of the argument-distributions in all of