Torture has been shown to be a reasonably good (though not always effective) means of getting people to tell torturers things that they think the torturers want to hear -- whatever the tortured person thinks is most likely to lead to the present cessation of the torture.

Its also been shown to be a fairly poor technique, compared to other alternatives, to get accurate, actionable information.

As the Senate report itself notes, this was the conclusion of the CIA's own work on interrogation techniques prior to 9/11, which was disregarded in the aftermath of 9/11.