Evolution of the Dual Route Cascaded Model of Reading Aloud

The time for skilled readers to name a non-word increases as the number of letters increase, and also increases when the stimulus is degraded. These effects are known as the length effect and stimulus quality effect, respectively. Besner and Roberts (2002) reported that the joint effect of these two factors on RT are additive in skilled readers. They also reported that the leading computational model of basic processes in reading, Coltheart, Rastle, Perry, Langdon & Ziegler’s Dual Route Cascaded model (2001), produces an under additive interaction between these two factors. Besner and Roberts argued that this qualitative difference challenges DRC’s fundamental assumption of cascaded processing. They proposed that thresholding early processing in the model would allow the model to simulate the human results. The present work implements such a threshold at the letter level in DRC. The new model successfully reproduces the joint effects of letter length and stimulus quality seen in skilled readers.