While there are opposing views about the mental representation of regular and irregular past tense verbs, numerous sources of evidence point to the greater complexity of irregular verbs (longer reaction times, later acquisition, regularization errors). This talk will focus on two aspects of complexity. First, it has been proposed, especially in dual mechanism accounts, that generation of irregular past requires blocking of the default regular –ed affix. Second, some lexical entries may include more than one past form, one for the simple past (e.g. began) and one for the past perfect (e.g. begun). In line with recent work on graded morphology (Hay & Baayen 2005), I will test if past tense verb forms exist on a continuum. I will argue that generation of past tense involves varying degrees of cognitive control, similar to the control exercised when suppressing a pre-potent response in Stroop tasks and low selectional constraints. However, the association between past tense generation and inhibitory control is yet to be examined. The proposed study will examine the link between verb past and cognitive control to 1) elucidate the mental processes underlying past tense generation and 2) account for the observed difficulties with tense marking in some persons with aphasia.