Dataset of the first study of my PhD on visual perception and alpha-phase in a real-time setup. The study is an adaptation of Callaway and Yeager (1960)'s study in Science. The dataset contains two types of data for each participant: RAW DATA EEG datasets in FieldTrip format from the following sessions: IAF dataset. Dataset from a 5min recording with the eyes closed to calculate the Individual Alpha Frequency (IAF). MCS dataset. Dataset containing data from a multiple constant stimuli (MCS) paradigm targetting 10 equally spaced bins along the whole alpha cycle. BCS dataset. Dataset containing data from a binary constant stimuli (BCS) paradigm targetting the associated fast/slow bins along the alpha cycle selected from the MCS dataset. ONLINE DATA Data acquired from the real-time EEG-based system recorded in MATLAB. There is information about each block in both MCS and BCS part of the experiment, together with the IAF used for each participant.