Abstract: A series of studies have demonstrated that saccadic target selection within alphabetic writing systems is based on words. Specifically, there is plenty of evidence that the observation of the optimal viewing location effect, in which words are identified most quickly when they are fixated close to the word center, and the preferred viewing location effect, in which landing positions on words are most commonly observed to be just to the left of the word centre. If word spaces are removed, the preferred viewing location is transferred to the word beginning. There is a heated debate, however, concerning the basic unit of saccadic target selection in non-alphabetic writing systems, such as Chinese, which is printed as continuous strings of characters without spaces between the words. It is intriguing whether the saccadic targets are selected on the basis of characters or words during Chinese reading.
In the present study, we selected readers with different native languages, with Chinese as a second language, to investigate the role of inter-word space on saccadic target selection during Chinese reading, especially to explore whether this effect was modulated by the familiarity of the presentation for their native languages.
The eye movements of 80 participants with Chinese as a second language, whose native languages were Korean, American, Japanese, and Thai were recorded with a SR Research EyeLink 1000 eye tracker (sampling rate = 1000 Hz) that monitored the position of the right eye every millisecond. All of the participants were instructed to read 64 Chinese sentences with two different presentation conditions (normal, unspaced condition and word-spaced presentation). For each participant, half of the sentences were presented in the normal, unspaced condition, and the other half were presented with word-spaced condition.
The results showed that there was a very similar pattern in the saccadic targeting selection for the four groups of second language learners, regardless of their native language: they showed a strong tendency to fixate the word center in single-fixation cases, and to fixate the word beginning in multiple-fixation cases. Furthermore, the proportion of the first fixation which located in the word center across the word-spaced condition is higher than that in the normal, unspaced condition, which indicated that the insertion of spaces between words partially guided the next saccadic target selection effectively. According to the theory of primary oculomotor control, we propose that readers with Chinese as a second language use “strategy-tactics” to guide their eye movements during Chinese reading.

Key words: readers with Chinese as a second language, inter-word space, saccadic target selection, landing position