The P3 was elicited in an active visual oddball task adapted from Luck et al. (2009). The letters A, B, C, D, and E were presented in random order (p = .2 for each letter). One letter was designated the target for a given block of trials, and the other 4 letters were non-targets. Thus, the probability of the target category was .2, but the same physical stimulus served as a target in some blocks and a nontarget in others. Participants responded whether the letter presented on each trial was the target or a non-target for that block. ---- The data are provided in three formats: I. A folder (**All Data and Scripts**) containing all of the raw and processed data files (including the results of intermediate processing steps), and the analysis scripts. II. A folder **(Raw Data and Scripts Only)** containing just the initial raw EEG data files and analysis scripts. The **Raw Data and Scripts Only** folder is much smaller, and the scripts can be used to create the intermediate processing data files. However, the **All Data and Scripts** option is useful if you have trouble getting the scripts to run or don’t want to re-run all of the processing steps. Within each folder, you will find: 1. Data files from 40 participants, located in subject folders 1-40 2. Archival copies of the EEGLAB/ERPLAB scripts and accessory files used for analyzing the data, located in "EEG_ERP_Processing," "Behavior_Measurements," and "Noise_Measurements" folders. The current versions of the scripts are hosted on GitHub (https://github.com/lucklab/ERP_CORE), and it is strongly recommended that these updated scripts are used instead of the archival copies found here. 3. The event code scheme for the task ("P3_Event_Code_Scheme.xlsx") 4. A spreadsheet containing demographic information for all 40 participants ("Participant_Demographics.xlsx") 5. A spreadsheet containing a list of participants included/excluded in the final analysis with reasons for exclusions ("P3_Subject_Summary.xlsx") 6. The versions of EEGLAB (v.13.4.4b) and ERPLAB (v.8.0.0) that were used in conducting the original analyses ("eeglab_13_4_4b.zip") III. A folder (**Raw Data BIDS-Compatible**) containing BIDS-formatted versions of the raw EEG files along with all the associated files required by the BIDS specification. --- For more details, please see the README file located in each folder