Failure to detect function word repetitions and omissions in reading: Are eye movements to blame?

We tested whether failure to notice repetitions of function words during reading (e.g., Amanda jumped off the the swing and landed on her feet.) is due to the eyes' tendency to skip one of the instances of the word. Eye movements were recorded during reading of sentences with repetitions of the word the or repetitions of a noun, after which readers were asked whether an error was present. A repeated the was detected on 46% of trials overall. On trials on which both instances of the were fixated, detection was still only 66%. A repeated noun was detected on 90% of trials, with no significant effect of eye movement patterns. Detecting an omitted the also proved difficult, with eye movement patterns having only a small effect. Readers frequently overlook function word errors even when their eye movements provide maximal opportunity for noticing such errors, but they notice content word repetitions regardless of eye movement patterns. We propose that readers overlook function word errors because they attribute the apparent error to noise in the eye movement control system.