“Double-Blind Tests of Subliminal Self-Help Audiotapes”, 1991-03-01 (; backlinks):
3 replications of a double-blind experiment tested subliminal audiotape products that were claimed to improve memory or to increase self-esteem. Conditions of use adhered to manufacturers’ recommendations, and subjects (n = 237) were limited to persons who desired the effects offered by the tapes.
Actual content and labeled content of tapes were independently varied, so that some subjects who believed they were using memory tapes were actually using self-esteem tapes, and vice versa.
After a month of use, neither the memory nor the self-esteem tapes produced their claimed effects.
Nevertheless, a general improvement for all subjects in both memory and self-esteem (a nonspecific placebo effect) was observed, and more than a third of the subjects had the illusion of improvement specific to the domain named on the tape’s label.