The 27th Language Lunch
Date: 2011-04-06
Location: G.07 Informatics Forum
Efficient CCG Parsing: A* versus Adaptive Supertagging
Michael,Auli; ILCC; m.auli@sms.ed.ac.uk
Naomi,Saphra; s1477768@sms.ed.ac.uk
We present a systematic comparison and combination of two orthogonal techniques for efficient parsing of Combinatory Categorial Grammar (CCG). First we consider adaptive supertagging, a widely used approximate search technique that prunes most lexical categories from the parser’s search space using a separate sequence model. Next we consider several variants on A*, a classic exact search technique which to our knowledge has not been applied to more expressive grammar formalisms like CCG. In addition to standard hardware-independent measures of parser effort we also present what we believe is the first evaluation of A* parsing on the more realistic but more stringent metric of CPU time. By itself, A* substantially reduces parser effort as measured by the number of edges considered during parsing, but we show that for CCG this does not always correspond to improvements in CPU time over a CKY baseline. Combining A* with adaptive supertagging decreases CPU time by 15% for our best model.
A Gricean Approach to the Gettier Problem
Allan,Hazlett; PPLS; ahazlett@staffmail.ed.ac.uk
The Gettier problem in epistemology is based our reluctance to attribute knowledge to people in certain kinds of situations (“Gettier cases”), despite their believing the truth with justification. This has led most people to conclude that the “tripartite analysis” of knowledge (on which knowledge = justified, true belief) is false. I defend the tripartite analysis by arguing that our reluctance to attribute knowledge in Gettier cases is explained by the fact that to do so would generate misleading conversational implicatures.
Working Memory Capacity and the Bilingual Dichotic Listening Task
Takayuki,Miura; Psychology; t.miura@sms.ed.ac.uk
This paper presents an experiment on the role of working memory capacity (WMC) among Japanese-English bilinguals when performing a bilingual dichotic listening (BDL) task. Previous studies have demonstrated a significant role for WMC in maintaining attention to the relevant stimuli and inhibiting irrelevant stimuli in monolingual dichotic listening. In the BDL task, in each ear, bilingual participants heard different concurrent texts which were semantically re/unrelated, and in the same language or in the two different languages. They also completed a test of WMC. The results showed that domain-general WMC predicted the ability to suppress the unattended language, regardless of its semantic relatedness to the language in the attended channel, especially when the attended language was English and the texts were read in different languages. This would demonstrate executive control of WMC in speech comprehension when bilinguals are required to maintain attention to one language and inhibit another.
RT to Win! Predicting Message Propagation in Twitter
Sasa,Petrovic; ILCC; sasa.petrovic@ed.ac.uk
Twitter is a very popular way for people to share information on a bewildering multitude of topics. Tweets are propagated using a variety of channels: by following users or lists, by searching, or by retweeting. Of these vectors, retweeting is arguably the most effective, as it potentially can reach the most people, given its viral nature. A key task is predicting if a tweet will be retweeted, and solving this problem furthers our understanding of message propagation within large user communities. A human experiment on the task of deciding whether a tweet will be retweeted shows that the task is possible, as human performance levels are much above chance. We present a machine learning approach, based on the passive-aggressive algorithm, that is able to predict retweets as well as humans. Analyzing the learned model, we find that performance is dominated by social features, but that tweet features add a substantial boost.
The Irrealis Subordinator If
Manuela,Rocchi; LEL; S0947649@sms.ed.ac.uk
In this paper I argue that English has a third type of if, that is, a declarative subordinator that introduces irrealis content clauses, as in (1): (1) I’d prefer if you stayed inside. I present evidence that strongly suggests that irrealis if-clauses are not ordinary conditional adjuncts, but function like VP-internal complements or subjects. In syntactic tests like extraction, preposing, clefting, and constituent order, irrealis clauses behave predominantly like complements, not adjuncts. Moreover, no other preposition with conditional or concessive meaning can be used to replace irrealis if. A close analysis of the semantics of irrealis clauses also points towards a non-conditional interpretation, as irrealis clauses refer to hypothetical states of affairs, but no idea of condition is implied in their meaning. Finally, I also discuss another candidate for the subordinator class, the wh-word when, which can often replace irrealis if (albeit without hypothetical meaning), as in (2): (2) I hate when this happens.
