What are the costs of degraded parafoveal previews during silent reading?

Abstract

It has been suggested that the preview benefit effect is actually a combination of preview benefit and preview costs. Marx et al. (2015) proposed that visually degrading the parafoveal preview reduces the costs associated with traditional parafoveal letter masks used in the boundary paradigm (Rayner,1975), thus leading to a more neutral baseline. We report two experiments of skilled adults reading silently. In Experiment 1, we found no compelling evidence that degraded previews reduced processing costs associated with traditional letter masks. Moreover, participants were highly sensitive to detecting degraded display changes. Experiment 2 utilized the boundary detection paradigm (Slattery, Angele, & Rayner, 2011) to explore whether participants were capable of detecting actual letter changes or if they were responding purely to changes in degradation. Half of the participants were instructed to respond to any noticed display changes; the other half were instructed to respond only to changes in letter identities. Participants were highly sensitive to degraded changes. In fact, these changes were so apparent that they reduced the sensitivity to letter masks. In the context of the model proposed by Angele, Slattery, and Rayner (2016), we suggest that degraded previews interfere with the attentional stage, as evidenced by the general lack of foveal load effects. In summary, we found that increasingly degrading parafoveal letter masks does not reduce their processing costs in adults, but that both degraded valid and invalid previews introduce additional costs in terms of greater display change awareness.