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Department of Cognitive Science

Seminar Abstract

Monkeys and metrics: What string distance measures can tell us about orthographic processing.

Speaker : Dr Emmanuel Keuleers, Department of Experimental Psychology, Ghent University, Belgium.
Date : 10th of July 2012, 4:00PM until 5:30PM
Location : C5C498 - Palermo Room, Macquarie University.

In a recent experiment, Grainger et al. (2012) showed that baboons learn to distinguish four-letter words from nonwords with an accuracy of about 75%. Whereas the authors defined orthographic processing as "the computation of letter identities and their relative positions", the representations and positional information required for this task remain unclear. We investigate the required level of orthographic processing in a lexical decision task using a nearest neighbor decision model (Keuleers & Brysbaert, 2011) extended with a Jaccard distance metric which can be made (in)sensitive to letter order and letter clusters. Simulations on the baboon data show that a non-positional single letter metric shows performance similar to that of baboons and that using bigrams and trigrams decreases performance, casting doubt on claims of advanced orthographic processing in baboons. Grainger, J., Dufau, S., Montant, M., Ziegler, J. C., & Fagot, J. (2012). Orthographic Processing in Baboons (Papio papio). Science, 336(6078), 245-248. Keuleers, E., & Brysbaert, M. (2011). Detecting inherent bias in lexical decision experiments with the LD1NN algorithm. The Mental Lexicon, 6(1), 34-52.