Data for: Classification accuracy alone cannot establish the neural origin of forehead EEG drowsiness estimates

This deposit contains the HARU-1 forehead EEG recordings of five participants (three channels at AFz, Fp1 and Fp2; 250 Hz; one session each) and the participant- and recording-level results behind every figure and table of the article “Classification accuracy alone cannot establish the neural origin of forehead EEG drowsiness estimates”. Labels are nominal protocol stages (task, early fixation, late fixation), not verified drowsiness states. The public datasets analysed in the article (Cao et al. 2019; the Cui et al. benchmark; Acı et al. 2019) are not redistributed. The absolute recording clock was replaced by elapsed time, and local computer paths inside the result files were replaced by placeholders; no value was changed. README.md describes the folders, columns and provenance. The recordings were made under approval 2024-518 of the Ethics Review Committee on Research with Human Subjects of Waseda University, with written informed consent.