Abstract: People are inclined to look for more diversity evidences to support the conclusion in their induction, because more diverse evidence leads to a stronger conclusion. This phenomenon is defined as the diversity effects of induction. Prior researches demonstrated that adults have this useful strategy for evaluating samples that contain single versus multiple pieces of evidence. However, there is a controversy regarding the criteria that children used to evaluate the multiple samples. The main debate is whether or not children who are younger than nine years old have diversity effects in their induction. Some researchers considered that children who are younger than nine years old do not attend to sample diversity to evaluate evidence, because there are important developmental changes in the mechanisms that support human induction. Other researchers held that young children have the diversity effects in their inductive reasoning. Those researchers suggest that the developmental changes underlie the inductive reasoning result from limitations in young children’s knowledge base. Therefore, they argued that the results that previous studies could not find children’s diversity performance are artificial as the paradigms or materials they used in their researches were unfit for young children.
In order to explore the problem whether young children have diversity effects, three experiments were performed. Experiment 1 used picture materials, and adopted the paradigm of Rhodes, etc. (2008a); twenty-four children at five years old and forty adults participated in this experiment. Experiment 2 used the same materials as experiment 1, but adopted a more direct technique paradigm; forty children at five years old participated in the experiment. Experiment 3 adopted the same method as experiment 1, but used common objects which children are familiar with as experimental materials; forty children at three years old participated in the experiment.
The results of experiment 1 indicated that adults had diversity effects in their induction, while five years old children had typicality effects but not diversity effects when they made induction of the animal pictures. This finding is consistent with the results of Rhodes, etc. (2008a). The results of experiment 2 demonstrated that children as young as five years old could utilize the diversity strategy in induction. The results of experiment 3 manifested that three-year-old children had diversity effects when they were making induction of familiar objects.
The findings of this article indicate that children as young as three years old could value diverse evidence in their inductive reasoning, which suggest that children may have diversity effects in inductive reasoning. The controversy whether children have diversity effects or not may mainly results from the different experimental paradigms and materials used by prior researchers. The reason why some previous studies have not found diversity effects of young children probably because they used unsuited detection paradigms or materials. The present work suggests that psychological experiment of young children should be done under appropriate experimental situation.

Key words: Children, Induction, Diversity effects, Typicality effects