Before its release in the United States, Sony decided that vibration feedback would be removed from the European and American versions of the controller. According to a Sony spokesperson, "We evaluated all the features and decided, for manufacturing reasons, that what was most important to gamers was the analog feature." Reasons for dropping the vibration feedback reportedly included its being linked to premature malfunction of the controllers. There were rumors that Nintendo had attempted to legally block the release of the controller in North America due to the vibration feature's similarity to Nintendo's Rumble Pak, but Nintendo firmly denied that it had taken any form of legal action over Sony's controllers. Moreover, according to the United States Patent Office, two employees of Atari Games have held a patent on vibrating game controller technology since March 1991. Another theory for the vibration feedback being dropped was that Sony simply wanted to keep the price of the controller down so as to maximize user adoption.