“…Time-domain measurements (linear analysis) record the variability of the successive heartbeats during the measured time periods. They include parameters such as mean RR, SDRR/SDNN, RMSSD, NN50, and pNN50 (Shaffer and Ginsberg, 2017;Drury et al, 2020 Assessing canine emotional states by implementing HRV indices has been gaining research popularity in recent years (Bergamasco et al, 2010;Gácsi et al, 2013;Bowman et al, 2015;Katayama et al, 2016;Travain et al, 2016;Zupan et al, 2016;McGowan et al, 2018;Köster et al, 2019). It has been proposed that HRV parameters might be sensitive indicators of emotional Poincaré plot representing the standard deviation perpendicular to the line of identity (the standard deviation of instantaneous beat-to-beat R-R interval variability) (Tulppo et al, 1996) SD2 ms 2 Poincaré plot representing the standard deviation along the line of identity (the standard deviation of continuous long-term R-R interval variability) (Tulppo et al, 1996) ApEn Approximate entropy, quantifying the regularity and complexity of a time series (Pincus et al, 1991) SampEn Sample entropy estimates the regularity and complexity of a time series (Richman and Moorman, 2000) DFA α1…”