Additive and Interactive Effects of Stimulus Degradation: No Challenge for CDP+

Johannes C. Ziegler, Conrad Perry, Marco Zorzi

Research output: Contribution to journalArticlepeer-review


S. O'Malley and D. Besner (2008) showed that additive effects of stimulus degradation and word frequency in reading aloud occur in the presence of nonwords but not in pure word lists. They argued that this dissociation presents a major challenge to interactive computational models of reading aloud and claimed that no currently implemented model is able to simulate additive effects in these conditions. In the current article, it is shown that the connectionist dual process model (CDP+) can simulate these effects because its nonlexical route is thresholded. The authors present a series of simulations showing that CDP+ can not only simulate the precise dissociation observed by O'Malley and Besner but more generally can produce additive effects for a wide range of parameter combinations and different sets of items. The nonlexical route of CDP+ was not modified post hoc to deal with the effects of stimulus quality, but it had been thresholded for principled reasons before it was known that these effects existed. Together, the effects of stimulus quality on word frequency do not challenge CDP+ but rather provide unexpected support for its architecture and processing dynamics.

Original languageEnglish
Pages (from-to)306-311
Number of pages6
JournalJournal of Experimental Psychology: Learning Memory and Cognition
Issue number1
Publication statusPublished - Jan 2009


  • additive effects
  • modeling
  • reading
  • stimulus quality
  • word recognition

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology


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