This paper studies the mechanisms behind the differential effects of inserting a space either before or after a two-character unit on information processing through the examination of eye movements in Chinese, a language where there is no word delimiters. A two-character unit in this study is either a word-preserving stimulus or a word-disrupting stimulus (i.e., nonword). The study aims for a better understanding of the cognitive mechanisms for lexical processing that may underlie observed facilitory or inhibitory effects of the spacing conditions in sentence context. Results show that inserting a space after a word facilitates lexical processing, but inserting a space before a word does not. Inserting a space before and after a nonword, however, does not show these effects. These results indicate that the effects of spaces before and after words are mainly influenced by word segmentation mechanisms rather than landing position effects or other factors.