It is a challenging task to measure consciousness. In this project, Ponce de Leon et al. (2025) propose the use of electroencaphalography (EEG) to evaluate the utility of two brain-based complexity measures – Lempel-Ziv complexity and the perturbational complexity index – in the study of conscious content. The overarching aim of the study is to investigate whether these two measures can discriminate between visual and auditory content varying in granularity levels. In addition to the main objectives, the authors plan to conduct a set of exploratory analyses.

 

The study will provide a significant contribution to the field by attempting to replicate effects previously reported in the literature and extending their generalisability through comparisons across varying configurations of the stimuli. The utility of these complexity measures within conscious content research will be further elucidated through exploratory regression analyses with behavioural variables and ratings of subjective experience.

 

The Stage 1 manuscript was evaluated over two rounds of in-depth review. Based on detailed responses to the recommender and reviewers' comments, the recommender judged that the manuscript met the Stage 1 criteria and therefore awarded in-principle acceptance (IPA). Ethics approval has not been granted yet, so this is a provisional IPA, which will be promoted to a full IPA once ethical approval is in place.

 

URL to the preregistered Stage 1 protocol: https://osf.io/kdsau (under temporary private embargo)

 

Level of bias control achieved: Level 6. No part of the data or evidence that will be used to answer the research question yet exists and no part will be generated until after IPA.
 
List of eligible PCI RR-friendly journals:

 

 
References

 

Ponce de Leon, S., Backer, K. C., Monti, M. M., & Yoshimi, J. (2025). Detecting differences in conscious contents using EEG complexity measures. In principle acceptance of Version 3 by Peer Community in Registered Reports. https://osf.io/kdsau