Fig. 2

Visualization and quantification of the complexity of actual experimental data. The data, obtained from an open dataset [225], contain a human respiratory signal while the participant watched a scary video. The respiratory signal is the temporal change in chest dimension associated with the expansion and contraction of the chest cavity, which was measured using a Hall effect sensor placed high on the torso. a The temporal change in chest dimension, sampled at 10 Hz, was used as the x variable for attractor reconstruction (b) and to generate the recurrence plot (c). b Three-dimensional plots of an attractor reconstructed using delay-time embedding (\(\tau =0.6\,\mathrm{ s})\). Variables y and z represent respiratory signals 0.6 s and 1.2 s advanced relative to the x variable, respectively. c Recurrence plot of human respiration while the participant watched a scary video (\(m=3, \tau =0.6\,\mathrm{ s}\), r = 0.8). d The log–log plot of a distance r versus the correlation sum C(r) has a linear scaling region, indicative of a fractal property. e The slope of the log–log plot (\(\frac{\mathrm{log}(C\left(r\right))}{\mathrm{log}(r)}\)) converges to 1.5 as the embedding dimension grows