In alphabetic scripts, the interword spaces can guide eye movement target selection, so readers adopt a word-based saccade target selection strategy. They usually select word center as their saccade target. However, in Chinese reading system, there are no interword spaces. This dissertation proposed a processing-based strategy for saccade target selection in Chinese reading in which readers estimate how many characters they can process on each fixation, and then program their next saccade so that the eyes fixate somewhere beyond. In this dissertation, the processing-based saccade target selection strategy was examined in the following three studies.
In Study 1, whether properties of words in a fixated region affect the length of the outgoing saccade was investigated. According to the processing-based saccade target selection, the easier the processing of the fixated region is, the longer the outgoing saccade will be. In Experiment 1, the critical region was a 4-character string which was either a word (one-word condition) or two 2-character word phrases (two-word condition). In Experiment 2, the critical region was either a high frequency word or a low frequency word. The outgoing saccade length from the last fixation on the critical region was longer in the one-word condition than the two-word condition in Experiment 1 and was longer in the high frequency condition than in the low frequency condition in Experiment 2. The results were consistent with the prediction of processing-based saccade target selection strategy.
In Study 2, the depth of reader processing the parafoveal information on a fixation was examined. A variant of the boundary paradigm was introduced in Experiment 3. In this paradigm, after the participant’s eyes crossed an invisible boundary, only a target character remained on the screen, displayed at the saccade landing site. The target character was either identical, orthographical or phonological similar to the first or second character after the boundary, or was a non-character. Readers were required to judge whether the target characters were real characters. The results showed that, when the first characters after the boundary were shown to readers, their reactions times (RTs) to the target characters were affected by landing position only in phonological similar condition. RTs were shorter as the landing position went further. When the second characters after the boundary were shown to readers, their RTs to the target characters were affected by landing position in the identical and orthographical similar condition.
RTs were shorter as landing position went further. These results are consistent with the predictions of a processing-based strategy. When a saccade is executed, the processing depth of variant properties of parafoveal information is different, which indicated that readers might program a saccade based on partial computation of information in fixated material.
In Study 3, the time at which the saccade program cannot be inhibited and whether this time would be affected by word frequency was explored. The paradigm in Experiment 4 combined stop signal paradigm with reading task. When readers’ eye moved across an invisible boundary, a stop sound was played after a delay. Readers were required to stop their eye movement when the sound was played. The results showd that the time for saccade programming till labile stage was about 105ms, and was not influenced by the word frequency of their fixated word. Readers cannot cancel or change the saccade program after this time.
In conclusion, this dissertation confirmed that Chinese readers do use a processing-based saccade target selection strategy. Readers estimate how many characters they can process on each fixation, and then program their next saccade so that the eyes fixate somewhere beyond them. This dissertation will help us develop a model that is best suitable for Chinese reading, and also improve our understanding on the mechanisms of eye movement control in Chinese reading and further the general mechanisms of reading among all the languages.