In social-cognitive research, little attention has been paid to the developmental course of spontaneous trait inferences about the actor (STIs about the actor) and spontaneous trait transferences about the informant (STTs about the informant). Using a false recognition paradigm, Study 1 investigated the developmental course of STIs and Study 2 investigated the developmental course of STTs, comparing 8-, 9-, 10-, 11-, 12- and 13-year olds. The results of Study 1 showed that 8-year olds could make STIs about the actor, and the magnitude of STIs increased from ages 8 to 10 years, stabilised at the age of 10, 11, 12 years, and decreased from ages 12 through 13 years. The results of Study 2 showed that 8-year olds could make STTs about the informant, and the magnitude of STTs did not vary with age. In all age groups, the magnitude of STIs about the actor was greater than that of STTs about the informant.