A meta-analysis on the influence of transcranial direct current stimulation (tDCS) on the processing of implicit associations (IATs)

Implicit prejudices are often costly to the self and others since implicit prejudices can impair cognitive functioning, social interactions, physical health, and psychological wellbeing (Brondolo et al. 2012; Gendler 2011; Maina et al. 2018). A variety of different interventions have, therefore, been used in an attempt to decrease implicit prejudice in participants, including psychopharmacology, interpersonal and imaginary contact, cognitive and emotional training, and adopting alternative perspectives through virtual embodiment (Maister et al. 2015; Paluck et al. 2021; Terbeck et al. 2012). Recently, brain stimulation techniques such as transcranial direct current stimulation (tDCS) have also been used with the goal of decreasing implicit prejudice in participants (Wang et al. 2019; Yuan et al. 2023). But, how effective, if at all, is tDCS at decreasing implicit prejudice? The purpose of this research is to address this question by systematically reviewing all relevant studies that compare the influence of tDCS versus sham stimulation on implicit prejudice, as measured by a variety of implicit association tests (IATs). Using a random effects model, this meta-analysis found a very small effect for the use of tDCS versus sham stimulation on decreasing implicit associations in women (k = 28, SMD = -0.140, p = 0.026). Yet, this research found a small effect for the use of tDCS versus sham stimulation on increasing implicit associations in men (k = 28, SMD = 0.252, p = 0.012). Here, I discuss the results of this research on tDCS and implicit associations, its practical value, and its limitations and prospects for future work.