The object of the study is preschoolers at the age of 5 and 6 years old. Children at this range of age has the ability of learning and accumulating vocabulary and the phenomenon of trials can be precisely observed for their quantity of correct choice of target word-referents in research. As cross-situational word learning has been proved to be a viable process that gets word learning off the ground, it is of much significance to testify the availability of this learning mechanism and demonstrate the effect of co-occurrence frequency on the preschool learners.

There are seven chapters organized in the thesis. Chapter one gives the introduction, including the background of the research and the questions which are going to be answered. Chapter two is the literature review which gives the readers a general knowledge of cross-situational word learning research and of some important researches to the present study. As for the following three chapters, they elaborately describe the design of the three experiments by providing the reader the information of participants, method, procedure and material, scoring, results and discussion, and preliminary analysis of data. Chapter six gives a general discussion of the whole research and limitation of the study. The last chapter gives a conclusion to the experiments, summarizing the present study.