Bayesian modeling of lexical knowledge acquisition in BRAID, a model of visual word recognition.

Bayesian modeling of lexical knowledge acquisition in BRAID, a model of visual word recognition.

First Author: Emilie Ginestet -- CNRS - Laboratoire de Psychologie et NeuroCognition
Additional authors/chairs: 
Sylviane Valdois; Julien Diard
Abstract / Summary: 

Purpose - There are several computational models of expert word recognition, expert word naming and eye movement control but very few attempts to mathematically model reading acquisition. In particular, modelling lexical orthographic knowledge acquisition is one of the main current challenges. Our team has recently developed a new Bayesian model of word recognition, called BRAID, to simulate expert readers’ performance. Here, we propose an extension of BRAID by implementing a mechanism for the acquisition of new orthographic knowledge.
Method - The BRAID model integrates an attentional component modelled by a Gaussian probability distribution; its parameters (muA ; sigmaA) respectively model the attentional focus point and the span of visual attention during letter-string processing. To model orthographic learning, we assume that visual attention displacements are chosen to optimize the accumulation of perceptual information about letters, so as to construct efficiently the new orthographic memory trace. To do this, we compute entropy gains so as to select parameters (muA ; sigmaA) of the next visual attention deployment.
Results - The results obtained during preliminary simulations suggest that, to acquire the spelling of a novel word, the model transitions from a letter-to-letter decoding strategy, when the word is first encountered, to a more global reading strategy, when some lexical information has already been memorized about the new word.
Conclusions - The plausibility of current results will be discussed by comparison with behavioural evidence on reading acquisition. We will further discuss the limits of our current model, which assumes a strictly orthographic word recognition process, without incorporating any phonological processing.