Background: Inhibitory control is a crucial executive function with high relevance to mental and physical wellbeing. However, there are still unanswered questions regarding its neural mechanisms, including the role of the major inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Aims: This study examined the effects of lorazepam (0.5 mg and 1 mg), a positive allosteric modulator at the GABAA receptor, on response inhibition and interference control. We also explored the heterogeneity of inhibitory control and calculated delta plots to explore whether lorazepam affects the gradual build-up of inhibition and activation over time. Method: A sample of N=50 healthy participants performed antisaccade, Eriksen flanker and Simon tasks in a within-subjects, placebo-controlled, double-blind randomised design. Results: Lorazepam increased mean reaction times (MRT) and error rates dose-dependently in all tasks (p≤.005). In the antisaccade and Simon tasks, lorazepam increased congruency effects for error rate (p≤.029) but not for MRT (p≥.587). In the Eriksen flanker task, both congruency effects were increased by the drug (p≤.031). Delta plots did not reflect any drug-induced changes in inhibition and activation over time. Delta plots for MRT in the Simon task were negative-going, as expected, whereas those for the antisaccade and flanker tasks were positive-going. Conclusions: This study provides clear evidence for GABAergic involvement in inhibitory control. Furthermore, our findings highlight the diversity of inhibitory control while also pointing out similarities between different inhibitory control tasks. In contrast to MRTs and error rates, the cognitive processes provided by delta plots appear not to be sensitive to GABAergic modulation.Draft version, 02.04.2020. This paper has not been peer reviewed. Please do not copy or cite without author's permission.