Noninvasive brain stimulation is becoming popular within sport as a way to improve motor performance, so much so that this ‘neuro-doping’ may provide a competitive edge in the future of sport. For example, Halo Sports is a popular commercialized product for delivering transcranial direct current stimulation (tDCS), which has been used by professional basketball players, NFL prospects, and US Ski and Snowboard athletes. tDCS is by far the most affordable and accessible stimulation technique by essentially applying very low electrical current (1-3 mA) to one’s scalp, and costs only ~$100-200 on Amazon (Halo Sports retails for $399). The low price and high access of tDCS make it a promising performance enhancement tool within recreational and professional sports.

The science behind tDCS, however, has not consistently shown that it outperforms placebo treatment in improving motor performance or training. What has been consistently demonstrated is widely varying responses to tDCS: some individuals improve following tDCS, while others do not. And still, others even show decrements. We think that such paradoxical findings may be due to an important, yet understudied factor: expectations about the effects of tDCS. Our central hypothesis is that people’s expectations about tDCS are partly responsible for how much they benefit from it. If a person expects a benefit from tDCS, there will be a positive outcome associated with tDCS, and the magnitude of the outcome is proportional to the level of expectation. The power of this expectancy effect has been well-documented in pain research, pharmacological studies, and psychiatry, but has been largely ignored by studies on tDCS and motor performance, despite motor performance itself being especially susceptible to expectations.

Thus, our proposed research will, by design, directly measure and control for expectations of tDCS using validated measures, and test whether higher expectations are associated with more improvement after tDCS. Our research is significant because we are among the first to explore the influence of expectations of tDCS for the purpose of enhancing motor performance. Our very preliminary data show that the general public does in fact show a wide range of expectations about how much tDCS would positively affect their motor performance. This strongly supports our hypothesis that the mixed effects of tDCS in previous studies can be attributed to unmeasured and widely variable expectations. Our preliminary data also show an important trend regarding gender differences in expectation: females’ expectations that brain stimulation will improve their motor performance are higher than that of males. This is very consistent with published reports of a female-specific effect of tDCS, and we argue that this is likely, not due to differences in brain anatomy/physiology, but rather gender differences in expectation. Thus, our research sits at the intersection of the current and past themes of the Global Sport Institute (namely, Sport 2036). This research is the first of its kind and can stimulate knowledge of whether, and how, brain stimulation enhances performance. This line of work will also inform how gender-dependent expectancy effects can be ethically leveraged for enhancing sports performance.

Read the final paper from this GSI-funded project here.

Last updated July 2021.