A familiar has an Intelligence score of at least 6, or higher if the master's level is 3rd or higher, as shown on page 53 of the Player's Handbook. The threshold for humanlike intelligence is 3 (see page 9 in the Player's Handbook), so a familiar is as smart as a person, but not necessarily as smart as a brilliant person or even an average person. A familiar's minimum Intelligence score of 6 makes it smart enough to understand at least one language, usually Common (though it doesn't gain the power of speech until the master reaches 5th level). This allows the familiar to respond to fairly elaborate commands and undertake fairly complex tasks. As rule of thumb, a 1st-level master's familiar is capable of doing anything a preadolescent human child can do. As the master's level increases, so does the familiar's ability to follow orders and perform tasks.
A familiar does not learn new languages as its Intelligence increases along with its master's level.
出自rotg,familiars,part 1