Distributional effects of word frequency on eye fixation durations

Recent research using word recognition paradigms, such as lexical decision and speeded pronunciation, has investigated how a range of variables affect the location and shape of response time distributions, using both parametric and non-parametric techniques. In this article, we explore the distributional effects of a word frequency manipulation on fixation durations in normal reading, making use of data from two recent eye movement experiments (Drieghe, Rayner, & Pollatsek, 2008; White, 2008). The ex-Gaussian distribution provided a good fit to the shape of individual subjects' distributions in both experiments. The frequency manipulation affected both the shift and skew of the distributions, in both experiments, and this conclusion was supported by the nonparametric vincentizing technique. Finally, a new experiment demonstrated that White's (2008) frequency manipulation also affects both shift and skew in response-time distributions in the lexical decision task. These results argue against models of eye movement control in reading that propose that word frequency influences only a subset of fixations and support models in which there is a tight connection between eye movement control and the progress of lexical processing.