Effects of efficient fronto-temporal circuitry on lexical ambiguity resolution: converging evidence from cross-age comparisons in eye-tracking and ERP data

Eye-tracking was used to examine how younger and older adults use syntactic and semantic information to disambiguate noun/verb (NV) homographs (e.g., park). We find that young adults exhibit inflated first fixations to NV-homographs when only syntactic cues are available for disambiguation (i.e., in syntactic prose). This effect is eliminated with the addition of disambiguating semantic information. Older adults (60+) as a group fail to show the first fixation effect in syntactic prose; they instead reread NV homographs longer. This pattern mirrors that in prior event-related potential work (Lee & Federmeier, 2009, 2011), which reported a sustained frontal negativity to NV-homographs in syntactic prose for young adults, which was eliminated by semantic constraints. The frontal negativity was not observed in older adults as a group, although older adults with high verbal fluency showed the young-like pattern. Analyses of individual differences in eye-tracking patterns revealed a similar effect of verbal fluency in both young and older adults: high verbal fluency groups of both ages show larger first fixation effects, while low verbal fluency groups show larger downstream costs (rereading and/or refixating NV homographs). Jointly, the eye-tracking and ERP data suggest that effortful meaning selection recruits frontal brain areas important for suppressing contextually inappropriate meanings, which also slows eye movements. Efficacy of fronto-temporal circuitry, as captured by verbal fluency, predicts the success of engaging these mechanisms in both young and older adults. Failure to recruit these processes requires compensatory rereading or leads to comprehension failures (Lee & Federmeier, in press).

Aging and semantic integration in sentence processing: Testing the cognitive workload of wrap-up

The current study investigated the cognitive workload of sentence and clause wrap-up in younger and older readers. A large number of studies have demonstrated the presence of wrap-up effects, peaks in processing time at clause and sentence boundaries that some argue reflect attention to organizational and integrative semantic processes. However, the exact nature of these wrap-up effects is still not entirely clear, with some arguing that wrap-up is not related to processing difficulty, but rather is triggered by a low-level oculomotor response or the implicit monitoring of intonational contour. The notion that wrap-up effects are resource-demanding was directly tested by examining the degree to which sentence and clause wrap-up affects the parafoveal preview benefit. Older and younger adults read passages in which a target word N occurred in a sentence-internal, clause-final, or sentence-final position. A gaze-contingent boundary change paradigm was used in which, on some trials, a non-word preview of word N+1 was replaced by a target word once the eyes crossed an invisible boundary located between words N and N+1. All measures of reading time on word N were longer at clause and sentence boundaries than in the sentence-internal position. In the earliest measures of reading time, sentence and clause wrap-up showed evidence of reducing the magnitude of the preview benefit similarly for younger and older adults. However, this effect was moderated by age in gaze duration, such that older adults showed a complete reduction in the preview benefit in the sentence-final condition. Additionally, sentence and clause wrap-up were negatively associated with the preview benefit. Collectively, the findings from the current study suggest that wrap-up is cognitively demanding and may be less efficient with age, thus, resulting in a reduction of the parafoveal preview during normal reading.

Formal and philological inquiries into the nature of interrogatives, indefinites, disjunction, and focus in Sinhala and other languages

In this thesis I examine a variety of linguistic elements which involve ``alternative'' semantic values---a class arguably including focus, interrogatives, indefinites, and disjunctions---and the connections between these elements. This study focusses on the analysis of such elements in Sinhala, with comparison to Malayalam, Tlingit, and Japanese. The central part of the study concerns the proper syntactic and semantic analysis of Q[uestion]-particles (including Sinhala "da", Malayalam "-oo", Japanese "ka"), which, in many languages, appear not only in interrogatives, but also in the formation of indefinites, disjunctions, and relative clauses. This set of contexts is syntactically-heterogeneous, and so syntax does not offer an explanation for the appearance of Q-particles in this particular set of environments. I propose that these contexts can be united in terms of semantics, as all involving some element which denotes a set of ``alternatives''. Both wh-words and disjunctions can be analysed as creating Hamblin-type sets of ``alternatives''. Q-particles can be treated as uniformly denoting variables over choice functions which apply to the aforementioned Hamblin-type sets, thus ``restoring'' the derivation to normal Montagovian semantics. The treatment of Q-particles as uniformly denoting variables over choice functions provides an explanation for why these particles appear in just this set of contexts: they all include an element with Hamblin-type semantics. However, we also find variation in the use of Q-particles; including, in some languages, the appearance of multiple morphologically-distinct Q-particles in different syntactic contexts. Such variation can be handled largely by positing that Q-particles may vary in their formal syntactic feature specifications, determining which syntactic contexts they are licensed in. The unified analysis of Q-particles as denoting variables over choice functions also raises various questions about the proper analysis of interrogatives, indefinites, and disjunctions, including issues concerning the nature of the semantics of wh-words and the syntactic structure of disjunction. As well, I observe that indefinites involving Q-particles have a crosslinguistic tendency to be epistemic indefinites, i.e. indefinites which explicitly signal ignorance of details regarding who or what satisfies the existential claim. I provide an account of such indefinites which draws on the analysis of Q-particles as variables over choice functions. These pragmatic ``signals of ignorance'' (which I argue to be presuppositions) also have a further role to play in determining the distribution of Q-particles in disjunctions. The final section of this study investigates the historical development of focus constructions and Q-particles in Sinhala. This diachronic study allows us not only to observe the origin and development of such elements, but also serves to delimit the range of possible synchronic analyses, thus providing us with further insights into the formal syntactic and semantic properties of Q-particles. This study highlights both the importance of considering various components of the grammar (e.g. syntax, semantics, pragmatics, morphology) and the use of philology in developing plausible formal analyses of complex linguistic phenomena such as the crosslinguistic distribution of Q-particles.

English syllable confusion and imitation in Korean bilingual and monolingual children and adults

In the present study, Korean-English bilingual (KEB) and Korean monolingual (KM) children, between the ages of 8 and 13 years, and KEB adults, ages 18 and older, were examined with one speech perception task, called the Nonsense Syllable Confusion Matrix (NSCM) task (Allen, 2005), and two production tasks, called the Nonsense Syllable Imitation Task (NSIT) and the Nonword Repetition Task (NRT; Dollaghan & Campbell, 1998). The present study examined (a) which English sounds on the NSCM task were identified less well, presumably due to interference from Korean phonology, in bilinguals learning English as a second language (L2) and in monolinguals learning English as a foreign language (FL); (b) which English phonemes on the NSIT were more challenging for bilinguals and monolinguals to produce; (c) whether perception on the NSCM task is related to production on the NSIT, or phonological awareness, as measured by the NRT; and (d) whether perception and production differ in three age-language status groups (i.e., KEB children, KEB adults, and KM children) and in three proficiency subgroups of KEB children (i.e., English-dominant, ED; balanced, BAL; and Korean-dominant, KD). In order to determine English proficiency in each group, language samples were extensively and rigorously analyzed, using software, called Systematic Analysis of Language Transcripts (SALT). Length of samples in complete and intelligible utterances, number of different and total words (NDW and NTW, respectively), speech rate in words per minute (WPM), and number of grammatical errors, mazes, and abandoned utterances were measured and compared among the three initial groups and the three proficiency subgroups. Results of the language sample analysis (LSA) showed significant group differences only between the KEBs and the KM children, but not between the KEB children and adults. Nonetheless, compared to normative means (from a sample length- and age-matched database provided by SALT), the KEB adult group and the KD subgroup produced English at significantly slower speech rates than expected for monolingual, English-speaking counterparts. Two existing models of bilingual speech perception and production—the Speech Learning Model or SLM (Flege, 1987, 1992) and the Perceptual Assimilation Model or PAM (Best, McRoberts, & Sithole, 1988; Best, McRoberts, & Goodell, 2001)—were considered to see if they could account for the perceptual and production patterns evident in the present study. The selected English sounds for stimuli in the NSCM task and the NSIT were 10 consonants, /p, b, k, g, f, θ, s, z, ʧ, ʤ/, and 3 vowels /I, ɛ, æ/, which were used to create 30 nonsense syllables in a consonant-vowel structure. Based on phonetic or phonemic differences between the two languages, English sounds were categorized either as familiar sounds—namely, English sounds that are similar, but not identical, to L1 Korean, including /p, k, s, ʧ, ɛ/—or unfamiliar sounds—namely, English sounds that are new to L1, including /b, g, f, θ, z, ʤ, I, æ/. The results of the NSCM task showed that (a) consonants were perceived correctly more often than vowels, (b) familiar sounds were perceived correctly more often than unfamiliar ones, and (c) familiar consonants were perceived correctly more often than unfamiliar ones across the three age-language status groups and across the three proficiency subgroups; and (d) the KEB children perceived correctly more often than the KEB adults, the KEB children and adults perceived correctly more often than the KM children, and the ED and BAL subgroups perceived correctly more often than the KD subgroup. The results of the NSIT showed (a) consonants were produced more accurately than vowels, and (b) familiar sounds were produced more accurately than unfamiliar ones, across the three age-language status groups. Also, (c) familiar consonants were produced more accurately than unfamiliar ones in the KEB and KM child groups, and (d) unfamiliar vowels were produced more accurately than a familiar one in the KEB child group, but the reverse was true in the KEB adult and KM child groups. The KEB children produced sounds correctly significantly more often than the KM children and the KEB adults, though the percent correct differences were smaller than for perception. Production differences were not found among the three proficiency subgroups. Perception on the NSCM task was compared to production on the NSIT and NRT. Weak positive correlations were found between perception and production (NSIT) for unfamiliar consonants and sounds, whereas a weak negative correlation was found for unfamiliar vowels. Several correlations were significant for perceptual performance on the NSCM task and overall production performance on the NRT: for unfamiliar consonants, unfamiliar vowels, unfamiliar sounds, consonants, vowels, and overall performance on the NSCM task. Nonetheless, no significant correlation was found between production on the NSIT and NRT. Evidently these are two very different production tasks, where immediate imitation of single syllables on the NSIT results in high performance for all groups. Findings of the present study suggest that (a) perception and production of L2 consonants differ from those of vowels; (b) perception and production of L2 sounds involve an interaction of sound type and familiarity; (c) a weak relation exists between perception and production performance for unfamiliar sounds; and (d) L2 experience generally predicts perceptual and production performance. The present study yields several conclusions. The first is that familiarity of sounds is an important influence on L2 learning, as claimed by both SLM and PAM. In the present study, familiar sounds were perceived and produced correctly more often than unfamiliar ones in most cases, in keeping with PAM, though experienced L2 learners (i.e., the KEB children) produced unfamiliar vowels better than familiar ones, in keeping with SLM. Nonetheless, the second conclusion is that neither SLM nor PAM consistently and thoroughly explains the results of the present study. This is because both theories assume that the influence of L1 on the perception of L2 consonants and vowels works in the same way as for production of them. The third and fourth conclusions are two proposed arguments: that perception and production of consonants are different than for vowels, and that sound type interacts with familiarity and L2 experience. These two arguments can best explain the current findings. These findings may help us to develop educational curricula for bilingual individuals listening to and articulating English. Further, the extensive analysis of spontaneous speech in the present study should contribute to the specification of parameters for normal language development and function in Korean-English bilingual children and adults.

Contextual text mining

With the dramatic growth of text information, there is an increasing need for powerful text mining systems that can automatically discover useful knowledge from text. Text is generally associated with all kinds of contextual information. Those contexts can be explicit, such as the time and the location where a blog article is written, and the author(s) of a biomedical publication, or implicit, such as the positive or negative sentiment that an author had when she wrote a product review; there may also be complex context such as the social network of the authors. Many applications require analysis of topic patterns over different contexts. For instance, analysis of search logs in the context of the user can reveal how we can improve the quality of a search engine by optimizing the search results according to particular users; analysis of customer reviews in the context of positive and negative sentiments can help the user summarize public opinions about a product; analysis of blogs or scientific publications in the context of a social network can facilitate discovery of more meaningful topical communities. Since context information significantly affects the choices of topics and language made by authors, in general, it is very important to incorporate it into analyzing and mining text data. In general, modeling the context in text, discovering contextual patterns of language units and topics from text, a general task which we refer to as Contextual Text Mining, has widespread applications in text mining. In this thesis, we provide a novel and systematic study of contextual text mining, which is a new paradigm of text mining treating context information as the ``first-class citizen.'' We formally define the problem of contextual text mining and its basic tasks, and propose a general framework for contextual text mining based on generative modeling of text. This conceptual framework provides general guidance on text mining problems with context information and can be instantiated into many real tasks, including the general problem of contextual topic analysis. We formally present a functional framework for contextual topic analysis, with a general contextual topic model and its various versions, which can effectively solve the text mining problems in a lot of real world applications. We further introduce general components of contextual topic analysis, by adding priors to contextual topic models to incorporate prior knowledge, regularizing contextual topic models with dependency structure of context, and postprocessing contextual patterns to extract refined patterns. The refinements on the general contextual topic model naturally lead to a variety of probabilistic models which incorporate different types of context and various assumptions and constraints. These special versions of the contextual topic model are proved effective in a variety of real applications involving topics and explicit contexts, implicit contexts, and complex contexts. We then introduce a postprocessing procedure for contextual patterns, by generating meaningful labels for multinomial context models. This method provides a general way to interpret text mining results for real users. By applying contextual text mining in the ``context'' of other text information management tasks, including ad hoc text retrieval and web search, we further prove the effectiveness of contextual text mining techniques in a quantitative way with large scale datasets. The framework of contextual text mining not only unifies many explorations of text analysis with context information, but also opens up many new possibilities for future research directions in text mining.