Table 5. Inter-correlations (Spearman’s Rho) between the sEMG signals (input), and the period P1–P4.

	corrms	corwl	orbrms	orbwl	levrms	levwl	zygrms	zygwl	risrms	riswl
periods P1–P4	0.302	0.328	0.149	0.210	0.200	0.218	0.065	0.127	0.153	0.183
	corrms	0.871	0.532	0.528	0.547	0.531	0.367	0.401	0.481	0.463
		corwl	0.489	0.559	0.488	0.554	0.332	0.437	0.454	0.512
			orbrms	0.832	0.798	0.732	0.751	0.668	0.750	0.659
				orbwl	0.713	0.803	0.637	0.760	0.693	0.768
					levrms	0.834	0.678	0.602	0.746	0.645
						levwl	0.616	0.694	0.692	0.747
							zygrms	0.759	0.780	0.659
								zygwl	0.695	0.807
									risrms	0.807

Muscle areas: cor = corrugator supercilii, orb = orbicularis oculi, lev = levator labii superioris, zyg = zygomaticus major, and ris = risorius; feature transformations: rms = root mean square, and wl = waveform length.