Effects of filler type in naming: change in time criterion or attentional control of pathways?

We report two naming experiments examining the effects of filler type on the size of regularity and frequency effects. Low-frequency exception words were used as one filler type in both experiments. Their effects were contrasted with the effects of nonword fillers (Experiment 1) and low-frequency regular word fillers (Experiment 2). In both experiments, the size of the regularity effect was unaffected by the filler type manipulation. In contrast, the frequency effect interacted with filler type such that relative to the low-frequency exception filler environment, the size of the frequency effect was reduced in the environment of low frequency regular word fillers, but not in the environment of nonword fillers. These results appear to be better explained in terms of Lupker, Brown, and Colombo's (1997) flexible time-criterion framework than in terms of a pathway control hypothesis (e.g., Zevin & Balota, 2000).