“…Based on the analyses conducted by Dixon and colleagues, we utilized two statistical techniques to examine pupil diameter fluctuations: Power Spectrum Density (PSD) for estimating power-law scaling (Hausdorff et al, 1995;Peng et al, 1995;Holden, 2005;Kello et al, 2007;Wijnants et al 2012a,b); and Recurrence Quantification Analysis (RQA) for estimating entropy, recurrence ratio, and determinism (Marwan and Kurths, 2002;Shockley, 2005;Orsucci et al, 2006;Marwan et al 2007;Bastos and Caiado, 2010;Ngamga et al, 2016;Lira-Palma et al, 2018;Morales-Bader et al, 2023).…”