Doctor Who: 10 Things Everyone Always Gets Wrong About The TARDIS
2. The TARDIS Is Merely A Machine
Though the TARDIS certainly looks like a machine, that's far from the truth.
Because of the manner of their creation, all TARDISes have some degree of sentience and some are capable of independent thought. TARDISes can communicate with each other psychically and can communicate with others - especially their pilots - non-verbally, if the person is skilled enough to realize the signs.
At first, even the Doctor did not realize the sentient nature of his TARDIS, but over time, began to realize that she was more than just a machine. He began referring to her as “Old girl.” He saw that she had quirks, he talked to her, he comforted her, and he stroked her console - much to the amusement of Sarah Jane Smith and Rose Tyler.
When the TARDIS matrix was placed in the body of Idris, any doubt of her sentience was dispelled. She told the Doctor that she chose him as much as he chose her, lamented his habit of bringing home “strays”, and expressed sadness at the deaths of her sisters. She also demonstrated her feelings of affection for the Doctor, especially enjoying that he calls her “sexy.”
Only when they're alone though!