Sham tACS controls succeeded because participants could not distinguish active from inactive

Evidence

The critical parameter was the relative timing of acoustic and electric stimulation (Fig. 1a ). This phase lag was manipulated across six conditions by varying the onset of the target in steps of 41.7 ms (30°) across the 4-Hz tACS cycles. Each experiment lasted 10 min. It was presented four times during continuous tACS and once without tACS. The latter sham stimulation was identical to tACS, except that the current was ramped down/up shortly after/before the experiment began/ended (Herrmann et al. 2013 ). Debriefings revealed that participants were unaware of whether they received tACS or sham stimulation. — Dijk, Pim van, Physiology, Psychoacoustics and…, 4777

Categorization

• CANDY: The detail that sham (ramped down) stimulation was indistinguishable from real tACS is a compact, surprising experimental-control fact.