Oculomotor inhibition of return in normal and mindless reading

Oculomotor inhibition of return (O-IOR) is an increase in saccade latency prior to an eye movement to a recently fixated location, as compared with other locations. To investigate O-IOR in reading, subjects participated in two conditions while their eye movements were recorded: normal reading and mindless reading with words replaced by geometric shapes. We investigated the manifestation of O-IOR in reading and whether it is related to extracting meaning from the text or is an oculomotor phenomenon. The results indicated that fixation durations prior to a saccade returning to the immediately preceding fixated word were longer than those to other words, consistent with O-IOR. Furthermore, fixation durations were longest prior to a saccade that returned the eyes to the specific character position in the word that had previously been fixated and dropped off as the distance between the previously fixated character and landing position increased. This result is consistent with the hypothesis that O-IOR is relatively precise in its application during reading and drops off as a gradient. Both of these results were found for text reading and for mindless reading, suggesting that they are consequences of oculomotor control, and not of language processing. Finally, although these temporal IOR effects were robust, no spatial consequences of IOR were observed: Previously fixated words and characters were as likely to be refixated as new words and characters.