Experiment 5: How irregular past-tense patterns are learned

This experiment aims to show what our learner can learn from irregular verbs. The input consists of 55 common irregular verbs (such as eat, blow, buy, go) and their past forms.

The learner acquires six rule-classifiers that cover 19 of the 55 input verbs:

[dc.dc.ae.ng]        rang, sang
[dc.dc.a.t]          forgot, got, shot
[dc.E.n.t]           bent, lent, meant, spent
[dc.dc.{r,l}.u]      blew, drew, grew
[dc.dc.).t]          bought, brought, caught, taught
[dc.dc.o.z]          chose, froze, rose

Since irregular verb forms are in general idiosyncratic and not productive (such as go/went), we expect they fall into many sub-classes. The results confirm our expectation. The learner is able to find the more common patterns (such as blew/drew/grew and bought/caught/taught). The results also suggest that most irregulars are just learned by rote and the learner makes few generalizations about these forms.