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Kristina Nilsson BjörkenstamUtbildningsledare

Om mig

Utbildningsledare, Samhällsvetenskapliga fakultetskansliet.

Fil. dr. i datorlingvistik.

Forskare i datorlingvistik (2011-2020). Studierektor för allmän språkvetenskap, fonetik och datorlingvistik på grundnivå och avancerad nivå (2017-2020) samt samordnande studierektor för lingvistik och teckenspråk (2018-2020) vid Institutionen för lingvistik, Stockholms universitet.

 

Publikationer

I urval från Stockholms universitets publikationsdatabas

  • Simulating Speech Error Patterns Across Languages and Different Datasets

    2021. Sofia Strömbergsson (et al.). Language and Speech

    Artikel

    Children's speech acquisition is influenced by universal and language-specific forces. Some speech error patterns (or phonological processes) in children's speech are observed in many languages, but the same error pattern may have different effects in different languages. We aimed to explore phonological effects of the same speech error patterns across different languages, target audiences and discourse modes, using a novel method for large-scale corpus investigation. As an additional aim, we investigated the face validity of five different phonological effect measures by relating them to subjective ratings of assumed effects on intelligibility, as provided by practicing speech-language pathologists. Six frequently attested speech error patterns were simulated in authentic corpus data: backing, fronting, stopping, /r/-weakening, cluster reduction and weak syllable deletion-each simulation resulting in a misarticulated version of the original corpus. Phonological effects were quantified using five separate metrics of phonological complexity and distance from expected target forms. Using Swedish child-speech data as a reference, phonological effects were compared between this reference and a) child speech in Norwegian and English, and b) data representing different modes of discourse (spoken/written) and target audiences (adults/children) in Swedish. Of the speech error patterns, backing-the one atypical pattern of those included-was found to cause the most detrimental effects, across languages as well as across modes and speaker ages. However, none of the measures reflects intuitive rankings as provided by clinicians regarding effects on intelligibility, thus corroborating earlier reports that phonological competence is not translatable into levels of intelligibility.

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  • Subjective ratings of age-of-acquisition: exploring issues of validity and rater reliability

    2019. Carla Wikse Barrow, Kristina Nilsson Björkenstam, Sofia Strömbergsson. Journal of Child Language 46 (2), 199-213

    Artikel

    This study aimed to investigate concerns of validity and reliability in subjective ratings of age-of-acquisition (AoA), through exploring characteristics of the individual rater. An additional aim was to validate the obtained AoA ratings against two corpora – one of child speech and one of adult speech – specifically exploring whether words over-represented in the child-speech corpus are rated with lower AoA than words characteristic of the adult-speech corpus. The results show that less than one-third of participating informants’ ratings are valid and reliable. However, individuals with high familiarity with preschool-aged children provide more valid and reliable ratings, compared to individuals who do not work with or have children of their own. The results further show a significant, age-adjacent difference in rated AoA for words from the two different corpora, thus strengthening their validity. The study provides AoA data, of high specificity, for 100 child-specific and 100 adult-specific Swedish words.

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  • Frequency filter: an open access tool for analysing language development

    2018. Paul Ibbotson, Rose M. Hartman, Kristina Nilsson Björkenstam. Language, Cognition and Neuroscience 33 (6), 1-15

    Artikel

    We present an open-access analytic tool, which allows researchers to simultaneously control for and combine language data from the child, the caregiver, multiple languages, and across multiple time points to make inferences about the social and cognitive factors driving the shape of language development. We demonstrate how the tool works in three domains of language learning and across six languages. The results demonstrate the usefulness of this approach as well as providing deeper insight into three areas of language production and acquisition: egocentric language use, the learnability of nouns versus verbs, and imageability. We have made the Frequency Filter tool freely available as an R-package for other researchers to use at https://github.com/rosemm/FrequencyFilter.

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  • Approximating phonotactic input in children’s linguistic environments from orthographic transcripts

    2017. Sofia Strömbergsson (et al.). Proceedings of the 18th Annual Conference of the International Speech Communication Association (INTERSPEECH 2017), Stockholm: The International Speech Communication Association (ISCA), 2017., 2214-2217

    Konferens

    Child-directed spoken data is the ideal source of support for claims about children’s linguistic environments. However, phonological transcriptions of child-directed speech are scarce,compared to sources like adult-directed speech or text data. Acquiring reliable descriptions of children’s phonological environments from more readily accessible sources would mean considerable savings of time and money. The first step towards this goal is to quantify the reliability of descriptions derived from such secondary sources. We investigate how phonological distributions vary across different modalities (spoken vs. written), and across the age of the intended audience (children vs. adults). Using a previously unseen collection of Swedish adult- and child-directed spoken and written data, we combine lexicon look-up and grapheme-to-phonemeconversion to approximate phonological characteristics. The analysis shows distributional differences across datasets both for single phonemes and for longer phoneme sequences. Some of these are predictably attributed to lexical and contextual characteristics of text vs. speech.The generated phonological transcriptions are remarkably reliable. The differences in phonological distributions between child-directed speech and secondary sources highlight a need for compensatory measures when relying on written data or onadult-directed spoken data, and/or for continued collection ofactual child-directed speech in research on children’s language environments.

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  • Modelling the Informativeness of Non-Verbal Cues in Parent–Child Interaction

    2017. Mats Wirén, Kristina N. Björkenstam, Robert Östling. Proceedings of Interspeech 2017, 2203-2207

    Konferens

    Non-verbal cues from speakers, such as eye gaze and hand positions, play an important role in word learning. This is consistent with the notion that for meaning to be reconstructed, acoustic patterns need to be linked to time-synchronous patterns from at least one other modality. In previous studies of a multimodally annotated corpus of parent–child interaction, we have shown that parents interacting with infants at the early word-learning stage (7–9 months) display a large amount of time-synchronous patterns, but that this behaviour tails off with increasing age of the children. Furthermore, we have attempted to quantify the informativeness of the different nonverbal cues, that is, to what extent they actually help to discriminate between different possible referents, and how critical the timing of the cues is. The purpose of this paper is to generalise our earlier model by quantifying informativeness resulting from non-verbal cues occurring both before and after their associated verbal references.

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  • Longitudinal Studies of Variation Sets in Child-directed Speech

    2016. Mats Wirén (et al.). The 54th Annual Meeting of the Association for Computational Linguistics, 44-52

    Konferens

    One of the characteristics of child-directed speech is its high degree of repetitiousness. Sequences of repetitious utterances with a constant intention, variation sets, have been shown to be correlated with children’s language acquisition. To obtain a baseline for the occurrences of variation sets in Swedish, we annotate 18 parent–child dyads using a generalised definition according to which the varying form may pertain not just to the wording but also to prosody and/or non-verbal cues. To facilitate further empirical investigation, we introduce a surface algorithm for automatic extraction of variation sets which is easily replicable and language-independent. We evaluate the algorithm on the Swedish gold standard, and use it for extracting variation sets in Croatian, English and Russian. We show that the proportion of variation sets in child-directed speech decreases consistently as a function of children's age across Swedish, Croatian, English and Russian.

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  • Modelling the informativeness and timing of non-verbal cues in parent–child interaction

    2016. Kristina Nilsson Björkenstam, Mats Wirén, Robert Östling. The 54th Annual Meeting of the Association for Computational Linguistics, 82-90

    Konferens

    How do infants learn the meanings of their first words? This study investigates the informativeness and temporal dynamics of non-verbal cues that signal the speaker's referent in a model of early word–referent mapping. To measure the information provided by such cues, a supervised classifier is trained on information extracted from a multimodally annotated corpus of 18 videos of parent–child interaction with three children aged 7 to 33 months. Contradicting previous research, we find that gaze is the single most informative cue, and we show that this finding can be attributed to our fine-grained temporal annotation. We also find that offsetting the timing of the non-verbal cues reduces accuracy, especially if the offset is negative. This is in line with previous research, and suggests that synchrony between verbal and non-verbal cues is important if they are to be perceived as causally related.

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  • SUC-CORE

    2013. Kristina Nilsson Björkenstam. Northern European Journal of Language Technology (NEJLT) 3 (2), 19-39

    Artikel

    This paper describes SUC-CORE, a subset of the Stockholm Umeå Corpus and the Swedish Treebank annotated with noun phrase coreference. While most coreference annotated corpora consist of texts of similar types within related domains, SUC-CORE consists of both informative and imaginative prose and covers a wide range of literary genres and domains.This allows for exploration of coreference across different text types, but it also means that there are limited amounts of data within each type. Future work on coreference resolution for Swedish should include making more annotated data available for the research community.

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  • Hybrid Methods for Coreference Resolution in Swedish

    2010. Kristina Nilsson (et al.).

    Avhandling (Dok)

    The aim of this thesis is to improve coreference resolution in Swedish by providing a hybrid approach based on combining data-driven methods and linguistic knowledge. Coreference resolution here consists in identifying all expressions in a text that have the same referent, for example, a person or an object.

    The linguistic knowledge is based on Accessibility Theory (Ariel 1990). This is used for guiding the  selection of likely anaphor-antecedent pairs from the set of all possible such pairs in a text. The data-driven method adopted is Memory-Based Learning (MBL), a supervised method based on the idea that learning means storing experiences in memory, and that new problems are solved by reusing solutions from similar experiences (Daelemans and Van den Bosch 2005).

    The referring expressions covered by the system are names, definite descriptions, and pronouns. In order to maximize performance, we use different classifiers with a specific set of linguistically motivated features for each type of expression. The great majority of features used for classification are domain- and language-independent.

    We demonstrate two ways of using this method of linguistically motivated selection of anaphor-antecedent pairs.

    First, the amount of training examples stored in memory  is reduced. We find that for coreference resolution of definite descriptions and names, the amount of training data can thereby be reduced with only a minor loss in performance, but for pronoun resolution there is a negative effect.

    Second, selection can be used for improving on coreference resolution results. This is the first step in our hybrid approach to coreference resolution, where the second step is the application of an MBL classifier for determining coreference between the selected pairs. Results indicate that this hybrid approach is advantageous for coreference resolution of definite descriptions and names. For pronoun resolution, there is a negative effect on recall along with a positive effect on precision.

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