Fig. 6

Linear regressions of ∆ grill heat (grill-induced increase in warm/heat sensation, panels b, d and f) and ∆ grill cold (grill-induced increase in cold sensation, panels a, c and e) with either CPT, HPT or ∆ thermal pain threshold (HPT versus CPT) as the only dependent variable. Data from male (N = 20) and female (N = 20) subjects are presented separately using different symbols and colours. As the thermal threshold values were not normally distributed (Kolmogorov-Smirnov test) Spearman’s correlation coefficient (ρ) was calculated to assess dependency between two variables. P < 0.05 after Bonferroni’s correction was considered significant and this is indicated by asterisks