Modelling the effect of literacy on multimodal interactions during spoken language processing in the visual world

Recent empirical evidence suggests that language-mediated eye gaze around the visual world varies across individuals and is partly determined by their level of formal literacy training. Huettig, Singh & Mishra (2011) showed that unlike high-literate individuals, whose eye gaze was closely time locked to phonological overlap between a spoken target word and items presented in a visual display, low-literate individuals eye gaze was not tightly locked to phonological overlap in the speech signal but instead strongly influenced by semantic relationships between items. Our present study tests the hypothesis that this behaviour is an emergent property of an increased ability to extract phonological structure from the speech signal, as in the case of high-literates, with low-literates more reliant on syllabic structure. This hypothesis was tested using an emergent connectionist model, based on the Hub-and-spoke models of semantic processing (Dilkina et al, 2008), that integrates linguistic information extracted from the speech signal with visual and semantic information within a central resource. We demonstrate that contrasts in fixation behaviour similar to those observed between high and low literates emerge when the model is trained on either a speech signal segmented by phoneme (i.e. high-literates) or by syllable (i.e. low-literates)