A mind-sifter (also referred to as a mind-scanner or mind-ripper) was a Klingon device used for interrogations in the 23rd century. The device operated by reaching directly into a subject's mind and recording thoughts and memories. It was designed with variable settings; at lower settings, it scans the surface thoughts of an individual, and causes no long-term damage. At higher settings, however, the procedure becomes much more invasive, recording all thoughts and memories of an individual, and emptying one's mind in the process.
Due to their intense mental discipline, Vulcans are more resistant to use of the mind-sifter. In 2267, while trapped on the planet Organia in the midst of a Klingon occupation, Spock was able to withstand and resist the effects of the device set on level four. Later, military governor Kor threatened to use the device on Captain James T. Kirk at the highest level, warning Kirk that the process would leave him little more than a mental vegetable. Before Kor could carry out his threat, the conflict between the Klingons and the Federation was halted by the intervention of the highly-advanced Organians. (TOS: "Errand of Mercy")