Transcranial direct current stimulation (tDCS) is a technique thought to modify cognition via a weak electric current applied to the scalp. Several thousand papers have been published since its inception in the early 2000s, with positive effects observed across healthy and patient samples in terms of language, memory, attention and various other executive functions. However, evidence is emerging that reported effects are exaggerated, and difficult to reproduce, especially in studies using single applications of anodal tDCS on healthy individuals. This thesis documents several studies that aimed to verify whether tDCS can modify word production, working memory and novel language acquisition in healthy participants when using conventional stimulation parameters, whilst considering factors that have driven its unreliability.