Editing Brain–computer interface (section)

=====Pupil-size oscillation=====
A 2016 article described a new non-EEG-based HCI that required no [[visual fixation]], or ability to move the eyes.<ref>{{cite journal |vauthors=Mathôt S, Melmi JB, van der Linden L, Van der Stigchel S |year=2016 |title=The Mind-Writing Pupil: A Human-Computer Interface Based on Decoding of Covert Attention through Pupillometry |journal=PLOS ONE |volume=11 |issue=2 |pages=e0148805 |bibcode=2016PLoSO..1148805M |doi=10.1371/journal.pone.0148805 |pmc=4743834 |pmid=26848745 |doi-access=free}}</ref> The interface is based on covert [[interest (emotion)|interest]]; directing attention to a chosen letter on a virtual keyboard, without the need to look directly at the letter. Each letter has its own (background) circle which micro-oscillates in brightness differently from the others. Letter selection is based on best fit between unintentional pupil-size oscillation and the background circle's brightness oscillation pattern. Accuracy is additionally improved by the user's mental rehearsal of the words 'bright' and 'dark' in synchrony with the brightness transitions of the letter's circle.