tDCS and tACS are non-invasive techniques that apply small electric currents (1-2 mA) to the scalp. These currents transiently modify local transneural electrical potentials in the brain, temporarily altering performance on a behavioral task. This approach allows us to directly investigate the causal role of specific brain hubs and networks in task performance.. To enhance the precision of tDCS and tACS in determining causal roles and to measure changes in neural activity, we will use structural and functional MRI on participants while they receive high-definition tDCS and tACS. Participants in the study will be trained on syllogistic reasoning tasks and then given unrelated tasks to assess the transfer from reasoning abilities.