Time Series Motif Discovery (TSMD) is defined as searching for patterns that are previously unknown and appear with a given frequency in time series. Another problem strongly related with TSMD is Word Segmentation. This problem has received much attention from the community that studies early language acquisition in babies and toddlers. The development of biologically plausible models for word segmentation could greatly advance this field. Therefore, in this article, we propose the Variable Input Length Map (VILMAP) for Motif Discovery and Word Segmentation. The model is based on the Self-Organizing Maps and can identify Motifs with different lengths in time series. In our experiments, we show that VILMAP presents good results in finding Motifs in a standard Motif discovery dataset and can avoid catastrophic forgetting when trained with datasets with increasing values of input size. We also show that VILMAP achieves results similar or superior to other methods in the literature developed for the task of word segmentation.
@cite_28: An important element of learning to read and write at school is the ability to define word boundaries. Defining word boundaries in text writing is not a straightforward task even for children who have mastered graphophonemic correspondences. In children’s writing, unconventional word segmentation has been observed across a range of languages and contexts with more occurrences of hyposegmentation (failure to separate two or more written words with a space) than hypersegmentation (written words are split into more than one segment). However, it is still unclear how frequent these errors are and the relationships of these written error patterns to the child’s development in oral language, spelling and reading remains relatively unexplored. To address these issues, unconventional written lexical segmentations in Brazilian Portuguese children’s text production during their first years at primary school (Year 1 to Year 3) were examined in relation to different cognitive and linguistic measures and patterns of spelling errors. Results reveal that in Portuguese the establishment of word boundaries in written text is not explained by visuospatial skills or limitations in processing resources (working memory). In contrast higher occurrences of hyposegmentation patterns were associated with lower levels of reading, vocabulary, verbal ability and morphological awareness whereas hypersegmentations were rarer and related to lower levels of reading and morphological awareness and typically only occurred in the initial stages of learning to write (Year 1). Occurrences of hyposegmentations as well as hypersegmentations were also related to spelling errors which reflected children’s poor phonological skills.
@cite_25: One of the infant’s first tasks in language acquisition is to discover the words embedded in a mostly continuous speech stream. This learning problem might be solved by using distributional cues to word boundaries — for example, by computing the transitional probabilities between sounds in the language input and using the relative strengths of these probabilities to hypothesize word boundaries. The learner might be further aided by language-specific prosodic cues correlated with word boundaries. As a first step in testing these hypotheses, we briefly exposed adults to an artificial language in which the only cues available for word segmentation were the transitional probabilities between syllables. Subjects were able to learn the words of this language. Furthermore, the addition of certain prosodic cues served to enhance performance. These results suggest that distributional cues may play an important role in the initial word segmentation of language learners. q 1996 Academic Press, Inc.
Unlike the spacing provided in the written text, the spoken words are rarely delimited by pauses, so children must learn somehow to identify the boundaries between words as they hear the sentences. Because the structure of words is significantly variable in all languages, it is difficult to know how a child between 9 and 15 months of age achieve this ability. Therefore, segmentation is a key step in language acquisition, specifically in lexical development @cite_25 . It is worth pointing out that finding the exact boundaries of all words in a sentence is not strictly necessary for children to understand what is said. They actually need to recognize the words present in the sentence (simple or compound) in the correct order, what can be done despite the occurrence of certain boundary detection errors, as it is observed in young children @cite_28 .