We are expected to behave appropriately to suit social situations. One form of behavioral control is the selection of a linguistic register that is appropriate to the listener. Register selection errors can sometimes be interpreted as rude behavior and result in having a bad influence on the relationship with the listener and the evaluation by other people. Previous studies have demonstrated that children begin to show sensitivity to registers from about 2 years of age, and that 5- to 6-year-old children understand the appropriate relationships between a listener and a register. However, it remains unclear whether and when children understand the influence made by register selection errors on listeners, and how children evaluate speakers when they make errors in register selection. Therefore, we investigated the above issues in Japanese children, who are required to use registers strictly. Also, we conducted a control study with Japanese-speaking adults to identify adults' evaluation of register selection errors. The results indicated that 7-year-old, but not 5-year-old children understood that the selection of an appropriate register gives listeners positive feelings. Moreover, 7-year-old children used register selection as an index of selective learning and social preference, although how they use others' register use skills for evaluating them was slightly different from adults. These results suggest that although children notice the social meanings behind the use of registers by the age of 7, a more extended period of development is required to master the social meaning of register selection.