Chaotic Response Suppression is a type of Vulcan mental discipline. It is taught to young Vulcans as a way to maintain logical thought regardless of exterior interference and stimuli. The technique is divided into two phases: Phase One involves clearing the mind and calming the mental process, a process likened to planting a garden where logic can bloom. Phase Two involves the use of logic to evaluate the stimuli and other variables, and dismissing irrelevancies.
Spock was presumably taught Chaotic Response Suppression as a young boy, and employed it to escape the effects of a Klingon mind-ripper. James Kirk, who had used the mind-ripper to enter Spock's mind and help pull him out, absorbed the knowledge of the technique, and was able to use it to ward off a Klingon attack during Spock's recovery. (TOS short story: "Chaotic Response")