A Joint Model of Word Segmentation and Meaning Acquisition Through Cross-Situational Learning

• Published in: Psychological review 2015-10, Vol.122 (4), p.792-829
• Main Authors: Räsänen, Okko, Rasilo, Heikki
• Format: Article
• Language: English
• Subjects: Babies; Cognitive models; Human; Humans; Infant Development; Language; Language Development; Learning; Learning - physiology; Models, Psychological; Psychology; Social interaction; Vocabulary development; Word Meaning; Words (Phonetic Units)
• ISSN: 0033-295X; 1939-1471
• DOI: 10.1037/a0039702

Human infants learn meanings for spoken words in complex interactions with other people, but the exact learning mechanisms are unknown. Among researchers, a widely studied learning mechanism is called cross-situational learning (XSL). In XSL, word meanings are learned when learners accumulate statistical information between spoken words and co-occurring objects or events, allowing the learner to overcome referential uncertainty after having sufficient experience with individually ambiguous scenarios. Existing models in this area have mainly assumed that the learner is capable of segmenting words from speech before grounding them to their referential meaning, while segmentation itself has been treated relatively independently of the meaning acquisition. In this article, we argue that XSL is not just a mechanism for word-to-meaning mapping, but that it provides strong cues for proto-lexical word segmentation. If a learner directly solves the correspondence problem between continuous speech input and the contextual referents being talked about, segmentation of the input into word-like units emerges as a by-product of the learning. We present a theoretical model for joint acquisition of proto-lexical segments and their meanings without assuming a priori knowledge of the language. We also investigate the behavior of the model using a computational implementation, making use of transition probability-based statistical learning. Results from simulations show that the model is not only capable of replicating behavioral data on word learning in artificial languages, but also shows effective learning of word segments and their meanings from continuous speech. Moreover, when augmented with a simple familiarity preference during learning, the model shows a good fit to human behavioral data in XSL tasks. These results support the idea of simultaneous segmentation and meaning acquisition and show that comprehensive models of early word segmentation should take referential word meanings into account.