Free association is a technique used in psychology, devised by Sigmund Freud.
Freud had abandoned hypnosis as a clinical technique, both because of its fallibility and because he found that patients could recover and comprehend crucial memories while conscious. Using the technique of free association, Freud asked patients to relate anything which came into their mind, regardless of how apparently unimportant or potentially embarrassing the memory threatened to be. This technique assumed that all memories are arranged in a single associative network, and that sooner or later the subject would stumble across the crucial memory.
Unfortunately, Freud found that despite a subject's every effort to remember, a certain resistance kept him from the most painful and important memories. He eventually came to understand that certain items were completely repressed, and off-limits to the conscious realm of the mind.
Freud's eventual practice of psychoanalysis focused not so much on the recall of these memories as on the internal mental conflicts which kept them buried deep within the mind, though the technique of free association still plays a role today in the study of the mind.