The zip file contains research data supporting the paper: Decreasing alertness modulates perceptual decision-making The files are arranged in the following manner: The raw data is present for 32 subjects used in the analysis. Each subject has a directory, for e.g. s_02 a) Inside this directory, there are two directories: awake: s_02_awake drowsy: s_02_drowsy b) The awake file has 124 trials, and the drowsy has 740 trials c) The files are .mff format (egi) and the coding is as follows: 'tone' - stimulus, 'RESP' - response. Each 'tone' is followed by a 'DIN2' marker, that marks when the stimulus was actually presented. 'summary_Righthanders.csv' contains the other details for all subjects, with subject id and whether the data was actually used for the analysis or not.