An incremental boundary study on parafoveal preprocessing in children reading aloud: Parafoveal masks overestimate the preview benefit

Parafoveal preprocessing is an important factor for efficient reading and, in eye-movement studies, is typically investigated by means of parafoveal masking: Valid previews are compared to instances in which masks prevent preprocessing. A long-held assumption was that parafoveal preprocessing, as assessed by this technique, only reflects facilitation (i.e., a preview benefit). Recent studies, however, suggested that the benefit estimate is inflated due to interference of the parafoveal masks, i.e., the masks inflict processing costs. With children from Grades 4 and 6, we administered the novel incremental priming technique. The technique manipulates the salience of the previews by systematically varying its perceptibility (i.e., by visually degrading the previews). This technique does not require a baseline condition, but makes it possible to determine whether a preview induces facilitation or interference. Our salience manipulation of valid previews revealed a preview benefit in the children of both Grades. For two commonly used parafoveal masks, we observed interference corroborating the notion that masks are not a proper baseline. With the novel incremental boundary technique, in contrast, one can achieve an accurate estimate of the preview benefit.