<qa>  What is the P3b index of target detection?2.3 Test Battery. 2.3.1 Visual Search Task. The visual search task will follow methodology described by Lorenzo-Lopez and colleagues and previously used in psychopharmacology research. In short, participants will be instructed to perform a visual search, which consists of detecting a target stimulus vertical bar among an array of distractors horizontal bars by indicating whether the target was present or absent in each search array by pressing a green button on a response pad with one hand and a red button with the other hand, respectively. Behavioral measures will include the number of correct responses, and the reaction times RTs of correct responses. Neural ERP measures of interest include the N2pc, an index of visual spatial shifts of attention to the location of the target or distractor, and the P3b, an index of target detection. The amplitudes of these ERPs indicate the amount of resources allocated to the associated cognitive process, while latency represents processing speed. Hypotheses: Caffeine will significantly speed up behavioural indices of target detection i.e. reduced RTs and associated neural waveforms i.e. reduced latency of N2pc P3b in both groups, with an increase in amplitude only observed in SZ patients. 