The Universal Electroencephalography Clip reduces hair-texture bias in electroencephalography

Standard electroencephalography (EEG) electrode caps, designed for fast and consistent placement, are incompatible with curly-to-coiled hair textures because electrodes cannot reliably reach the scalp. This disproportionately affects specific ethnic groups.

We developed the Universal Electroencephalography Clip (UE-C) for data collection across hair types and styles without requiring braiding procedures. We tested auditory and visual responses to assess signal quality across scalp regions. 57 participants (37 straight-to-wavy; 20 curly-to-coiled hair) heard auditory clicks at 4 Hz and viewed contrast-reversing gratings at 4/6Hz during EEG recording with the UE-C and the EEG cap. Epoch retention after artifact rejection and Signal-to-Noise Ratios (SNR) were compared across methods using ANOVAs and percent signal gain.

The UE-C retained more epochs at both visual (+10% curly-to-coiled; +12% straight-to-wavy) and auditory regions (+8% curly-to-coiled; -8% straight-to-wavy) relative to the cap. Visual 4-Hz SNR was enhanced (p = 0.01) with straight-to-wavy, not curly-to-coiled (p = 0.06). SNRs improved at visual sites (signal gain: +34%; curly-to-coiled; +30% straight to wavy). Negligible effects were observed at the auditory site, where the electrode-to-scalp problem is less likely.

At the visual electrode, the UE-C retained more data with improved signal quality over the cap, despite hair texture. Auditory-site data were comparable between methods. The UE-C performed similarly to the SEVO clip, without braiding requirements and accommodating various hairstyles.

We demonstrated another example of the electrode-to-scalp problem and share findings that offer a step forward toward correcting the hair bias in EEG methodology.