Investigating the validity of muscle response testing: Blinding the patient using subliminal visual stimuli

Research objective\ud To determine if Muscle Response Testing (MRT) can be used to distinguish lies from truths using blind test patients.\ud \ud Design\ud A prospective study of diagnostic test accuracy was carried out using MRT to distinguish lies from truth.\ud \ud Methods\ud Twenty practitioners who routinely practised MRT were paired with 20 blind test patients (TPs). TPs were asked to speak simple true and false statements about visual stimuli presented subliminally (at 20 ms). In the subliminal phase, pairs performed 20 MRTs and 20 Intuitive Guesses (IG), consisting of 2 blocks of 10 statements each. In the Supraliminal Phase, the same picture-statement pairs were repeated. The order of stimuli presentation was randomly assigned so that each pair was presented with a unique series of stimuli.\ud \ud Results\ud In the Subliminal Phase, MRT accuracy (as percent correct) was found to be 48.5% (95% CI 42.8–54.2), which was no different from IG accuracy (47.8%; 95% CI 43.2–52.3; p = 0.68) or chance (50.0%; p = 0.59), and no different from MRT accuracy during the supraliminal phase (59.0%; 95% CI 50.4–67.6; p = 0.05). However, supraliminal MRT accuracy was significantly different from chance (p = 0.04), indicating that the pairs could perform MRT proficiently.\ud \ud Conclusion\ud The main reason for finding no effect is suspected to be due to an inadequate subliminal methodology, a process which is quite complex. Other explanations of results include: (1) MRT is not a valid test when the TP is blind, (2) Blinding TPs during MRT will produce ambiguous or unpredictable results, or (3) Nonconscious beliefs cannot be elicited using subliminal stimuli. Future research may wish to focus on exploring these possibilities. More specifically, subsequent studies may wish to use different methods to blind TPs, and establish whether MRT can be used to detect nonconscious processes, a generally held consensus among MRT practitioners.