Regressions during reading: The cost depends on the cause.

The direction and duration of eye movements during reading is predominantly determined by cognitive and linguistic processing, but some low-level oculomotor effects also influence the duration and direction of eye movements. One such effect is inhibition of return (IOR), which results in an increased latency to return attention to a target that has been previously attended (Posner & Cohen, Attention and Performance X: Control of Language Processes, 32, 531-556, 1984). Although this is a low level effect, it has also been found in the complex task of reading (Henderson & Luke, Psychonomic Bulletin & Review, 19(6), 1101-1107, 2012; Rayner, Juhasz, Ashby, & Clifton, Vision Research, 43(9), 1027-1034, 2003). The purpose of the current study was to isolate the potentially different causes of regressive eye movements: to adjust for oculomotor error and to assist with comprehension difficulties. We found that readers demonstrated an IOR effect when regressions were caused by oculomotor error, but not when regressions were caused by comprehension difficulties. The results suggest that IOR is primarily associated with low-level oculomotor control of eye movements, and that regressive eye movements that are controlled by comprehension processes are not subject to IOR effects. The results have implications for understanding the relationship between oculomotor and cognitive control of eye movements and for models of eye movement control.