Spanish verbal inflection: a single- or dual-route system?

Four studies of Spanish morphology are examined that seem to support the dual-route model because they demonstrate an asymmetry between regular and irregular verbal inflection. Yaden's subjects (2003) produced inflected forms of infinitives in which many errors that regularized irregular inflections were produced, but few that irregularized regulars. Clahsen et al. (2002) also found more regularization than irregularization errors in children's speech. However, single-route analogical computer simulations of Yaden's test items and of errors in simulated acquisition yielded the same dissociation between common regularization uncommon irregularization. The experiment by Brovetto and Ullman (2005) entailed inflecting nonce verbs. They argue that two factors influence inflection: the phonological similarity of the nonce stem to extant stems and the verb's conjugational class. They found that phonological similarity only influenced irregularization of words with rimes commonly found in irregular verbs, but not words with rimes common in regular verbs. However, stem similarity and conjugational class are both represented phonologically in the nonce words making them available to influence the nonce words analogically. A single-route simulation of Brovetto and Ullman's test items produced similar outcomes. Because a single-route model can produce the same dissociation between regular and irregular inflections, the data from the cited experiments do not demonstrate the superiority of the dual-route model. In Rodriguez-Fornells et al. (2002), ERPs were measured during a priming study. Regular targets demonstrated an increased positivity between 250 and 450 ms after the presentation of the stimulus, but irregulars did not. However, these findings are suspect because it is not possible to control for the effects of previous knowledge of the word, orthographic overlap, and semantic similarity at the same time. In addition, alternative explanations of the such differences exist which do not require positing different mechanisms for regular and irregular inflection.