Henry Kissinger’s Sentiments Are Not An Exception!
Posted on September 12, 2012 by Walid Saba
I have received many comments on the short article “Henry Kissinger vs. Sentiment Analysis” (Saba, 2012). The main point of that article was that the sentence in (1) conveys an extremely positive sentiment about the United States, although a purely quantitative (statistical or machine learning) approach cannot make this inference due to the surrounding negative words in the context.
1. The US is the worst place to live in, until you try living anywhere else.
The argument made in (Saba, 2012) was this: sentiment analysis presupposes understanding ordinary spoken language, and is even much harder as it requires understanding metaphor, sarcasm, irony, etc. Since we do not yet have systems that can even understand simple and ordinary spoken language, there cannot be any system that does serious and meaningful sentiment analysis. While most comments received were in agreement, there were some comments that questioned the percentage of such examples in everyday language use. These (noteworthy) comments can be summarized as follows:
If the (Henry Kissinger, the corner table, and the iPhone) examples I provided are not an exception but actually constitute a large percentage of everyday language use, then the argument that there cannot be sentiment analysis before we have full natural language understanding is accepted. If, on the other hand, these examples are a small percentage of everyday language use, then statistical and machine learning approaches can indeed do a decent job in inferring positive and negative sentiment in text.
This, I confer, is a sound observation that is worthy of discussion.
In what follows I hope to show that examples involving sarcasm, metonymy, irony, metaphor, etc. are not rare or exceptional, but are in fact quite common in everyday language use. Programs that process and comprehend such sentences must therefore have access to a massive amount of “commonsense knowledge” and will need to make very complex inferences to decode what is hidden or missing from the utterances people make.
Once the argument is made that such utterances are not an exception in everyday language use, but are in fact quite common, there remains one argument that can support the claim that there are currently systems that can do meaningful sentiment analysis: to prove that there are systems that can understand one simple question posed in ordinary spoken language, which is a challenge that I will gladly accept.
Non-Literal Meaning In Everyday Language Use
The sentence in (1), which expresses a positive sentiment towards the US, despite the apparent use of negative terminology, uses what is technically referred to in linguistics as “sarcasm”. Other examples that require deep natural language understanding (involving the use of commonsense and logical reasoning) involve the use of “metonymy”. For example, consider the following, quite common and not at all exotic and rare utterances:
1. I don’t like Barcelona; Real Madrid was always my favorite.
2. Americans do not like to talk about Vietnam, it brings back so much bad memories.
Clearly, the (very ordinary and common!) utterance in (2) is not anyway conveying a negative sentiment about the city of Barcelona, but the football (soccer!) team of that city. The speaker could very well like the city of Barcelona, but it happens that his favorite team is Real Madrid. Similarly for (3). The negative context surrounding ‘Vietnam’ is no indication at all of American sentiment towards the country, but a particular event, namely the long and very bloody Vietnam War.
This use of one entity to refer to another is quite common. In fact, some researchers claim that the percentage of metonymy in ordinary language use is (alone!) somewhere between 17% to 20% (for an example, see Markert and Nissim, 2006). This percentage is much higher in other forms of text, such as political talk, poetry, the arts, etc. The same applies to sarcasm and irony, which Chin (2011) says is “practically the primary language” in modern society. Like metonymy, sarcasm is quite common yet it presents sentiment analysis with a monumental challenge. Consider these very ordinary and quite common utterances:
3. Yes, Porsche is too expensive, but let’s face it, it is one hell of a car.
4. There’s so much to curse and nag about in New York, but if I leave for one week, I miss it.
The context surrounding ‘Porsche’ and ‘New York’ in (4) and (5) seems to be quite negative, yet a full understanding that relies on background and commonsense knowledge would allow us to make the right inferences – that Porsche is a great car and, despite of all the negatives, New York city has a lot to offer!
Besides sarcasm, irony and metonymy, which alone account to more than 30% of ordinary language use, metaphor is also quite common in text, amounting to more than 50% of ordinary language use, according to some researchers (see, for example, Lakoff and Johnson, 1980; Paloma Úbeda Mansilla, 2003). Sentences that are full of metaphorical use, such as that in (6) are also quite common and are also beyond any quantitative and machine learning approaches to sentiment analysis.
6. Man, look at that wild and crazy thing, she is a knockout!
To summarize, studies indicate that, collectively, metonymy, metaphor, sarcasm, irony, and other forms of non-literal use of words in ordinary spoken language are not an exception but the norm in ordinary language use. In fact, ordinary, simple and straight to the point language is the exception (unless the target audience were young children that have not yet mastered the interpretation of such language). This is especially the case when it comes to social media jargon, where sarcasm, irony and other forms of non-literal language is the norm. Assuming these forms of language use are an integral part of ordinary text (say 60% of language use), then a sentiment analysis system that has a statistical and machine learning system with 80% accuracy can at best make around 60% accurate inferences regarding sentiment. This is only slightly better than making random picks between heads (negative sentiment), or tails (positive sentiment)!
One final word regarding this subject – Like we mentioned in an earlier article, we are not in any way questioning the value of work in natural language processing. We ourselves are actively working in this field and we have recently developed a semantic engine that is excellent at inferring the “aboutness” of a piece of text, producing an intelligent summary, identifying the key topics, extracting entities and inferring their type, as well as relating textual objects semantically.
Inferring the aboutness of a piece of text, and semantically/topically relating text, can be done, although it has not been perfected. However, saying that there are currently systems that can infer from what we write how we ‘feel’ about certain entities is not only inaccurate, but is harmful. When expectations are not met, it will not be easy to recover when the time comes to do “real” sentiment analysis.
Chin, R. (2011), The Science of Sarcasm? Yeah, Right, Science and Nature, Nov. 4, 2011
Gibbs, R. W. and Colston, H. L. (2001), The Risks and Rewards of Ironic Communication, In L. Anolli, R. Ciceri and G. Riva (Eds.), New perspectives on miscommunication, IOS Press, 2001
Lakoff, G. and Johnson, M. (1980), Metaphors we Live by, University of Chicago Press.
Markert, K. and Nissim, M. (2006), Metonymic Proper Names: A Corpus-based Account, In A. Stefanowitsch, editor, Corpora in Cognitive Linguistics. Vol. 1: Metaphor and Metonymy. Mouton de Gruyter, 2006.
Paloma Úbeda Mansilla (2003), Metaphor at work: a study of metaphors used by European architects when talking about their projects, IBÉRICA 5