(i.e. better memory for interrupted rather than completed tasks). Horizontal eye movement triggers an evolutionary 'orienting response' in the brain, used in scanning the environment for threats and opportunities. EMDR gives an effect similar to the effects of sleep, and posit that traumatic experiences are processed during sleep. Trauma can be overcome or mastered, and EMDR facilitates a form of mindfulness or other forms of mastery over the trauma. A 2013 meta-analysis focused on two mechanisms: (1) taxing working memory and (2) orienting response/REM sleep. It may be that several mechanisms are at work in EMDR. Bilateral stimulation, including eye movement Bilateral stimulation is a generalization of the left and right repetitive eye movement technique first used by Shapiro. Alternative stimuli include auditory stimuli that alternate between left and right speakers or headphones and physical stimuli such as tapping of the therapist's hands or tapping devices. Research has attempted to correlate other types of rhythmic side-to-side stimuli, such as sound and touch, with mood, memory, and cerebral hemispheric interaction. Francine Shapiro noticed that eye movements appeared to decrease the negative emotion associated with her own distressing memories. Bilateral stimulation seems to cause dissipation of emotions. Research results and opinions have been mixed on the effectiveness and importance of the technique; A 2000 review found that the eye movements did not play a central role, and that the mechanisms of eye movements were speculative. A 2001 meta-analysis suggested that EMDR with the eye movements was no more efficacious than EMDR without the eye movements (Davidson & Parker, 2001). A 2002 review reported that the eye movement is irrelevant, and that the effectiveness of EMDR was solely due to its having properties similar to CBT, such as desensitization and exposure. A 2012 review found that the evidence provided support for the contention that eye movements are essential to this therapy and that a theoretical rationale exists for their use. A 2013 meta-study found the effect size of eye movement was large and significant, with the strongest effect size difference being for vividness measures. A 2020 systematic review and meta-analysis including nine dismantling randomized controlled trials of EMDR with or without bilateral eye-movements found that the efficacy between EMDR with and without eye-movements were negligible to non-existent. 2020 research showed that bilateral alternating stimulation caused a significant increase in connectivity between several areas of the brain, including the two superior temporal gyri, the