Temporal variation in the acoustic dynamic range is a confounding factor in EEG-based tracking of absolute auditory attention to speech

Abstract Many studies have demonstrated that auditory attention to natural speech can be decoded from EEG data. However, most studies focus on selective auditory attention decoding (sAAD) with competing speakers, while the dynamics of absolute auditory attention decoding (aAAD) to a single target remains underexplored. The goal of aAAD is to measure the degree of attention to a single speaker, and it has applications for objective measurements of attention in psychological and educational contexts. To investigate this aAAD paradigm, we designed an experiment where subjects listened to a video lecture under varying attentive conditions. We trained neural decoders to reconstruct the speech envelope from EEG in the baseline attentive condition and use the correlation coefficient between the decoded and real speech envelope as a metric for attention to the speech. Our analysis shows that the envelope standard deviation (SD) of the speech envelope in the 1-4 Hz band strongly correlates with this metric across different segments of the speech stimulus. However, this correlation weakens in the 0.1-4 Hz band, where the degree of separation between the attentive and inattentive state becomes more pronounced. This highlights the unique contribution of the 0.1-1 Hz range, which enhances the distinction of attentional states and remains less affected by confounding factors such as the time-varying dynamic range of the speech envelope. Competing Interest Statement The authors have declared no competing interest. Footnotes * This project has received funding from Internal Funds KU Leuven (project IDN/23/006), the FWO (Research Foundation Flanders) for project G081722N and the Junior Postdoctoral Fellowship for Fundamental Research awarded to S. Geirnaert (No. 1242524N) and E. Bellon (No. 12C9523N), and the European Research Council (ERC) (grant agreement 101138304). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or ERC. Neither the European Union nor the granting authority can be held responsible for them. Add a new reference, correct a few errors, polish the language a bit