Investigating oculomotor control during the learning and scanning of character strings

Abstract

Word spacing plays an important role in both word identification and saccadic targeting in the reading of spaced languages (e.g., English), however, the spacing facilitation is not present when word spacing is added in normally unspaced Chinese text in Chinese native speakers (e.g., Grade-3 children, young adults, old adults). Frequency effects are well-documented in the reading of normal text. However, it remains controversial as to whether frequency effects would occur in non-reading tasks, such as searching for a target in normal text or text-like strings. Furthermore, it is unclear whether spacing would also play an important role in the guidance of eye movement control in text-like string scanning as it does in the reading of spaced languages.

In three experiments, the present thesis examined how exposure frequency effects are established during the learning of novel stimuli in a learning session (Landolt-C clusters in Experiment 1 vs. pseudowords in Experiments 2 & 3) and how the simulated exposure frequency would affect the scanning of longer strings with or without boundary demarcation cues (spaced vs. unspaced shaded vs. unspaced) in a scanning session. Importantly, the present thesis investigated whether learning and scanning of novel character strings would be qualified by the stimulus type (Landolt-C vs. English pseudoword) and the population (English native speakers vs. Chinese participants).

In Experiment 1, robust interactive effects between exposure frequency and learning blocks (e.g., learning rate effects) occurred during the learning of target stimuli. However, the exposure frequency effects did not carry over to the scanning session. Robust spacing effects occurred. Spacing facilitated eye movements to a greater degree than the shading manipulation. In Experiments 2 & 3, again, robust learning rate effects occurred in learning target pseudowords. The exposure frequency was simulated successfully and effectively during learning, however, the exposure frequency showed no influence on eye movements in the scanning session. The meta-analysis across the three experiments demonstrated that learning was more effective using pseudoword stimuli relative to Landolt- C stimuli, and more effective in Chinese participants than English participants. Generally, the degree of shading facilitation was much smaller in the scanning of Landolt-C strings compared to pseudoword strings and it was smaller for English participants relative to Chinese participants. The constant occurrence of learning rate effects across experiments suggests the replicability and reliability of the current character learning paradigm. Spacing facilitation constantly occurred in scanning either Landolt-C strings or pseudoword strings, indicating that spacing plays an important role in non-reading string scanning tasks. The absence of exposure frequency effects in the scanning session across three experiments seems to suggest that exposure frequency effects might not occur in string scanning when the task is to search for a pre-learnt target in the string. The differential pattern of shading and spacing facilitation between Chinese participants and English participants suggests an influence from the writing system of the native language on eye movements in the current string scanning.