Split-plot ANOVA revealed a highly significant main effect of contrast (F 2,52 = 37.19; p < .0001) and interaction between group and contrast (F 2,52 = 8.07; p < .001); the main effect of group was not significant (F 1,26 = 0.22; p = .64).
Correlation between increment thresholds and age for control subjects did not reach statistical significance in any test condition; however, all correlations were positive (range: r = 0.23–0.36) suggesting that age might contribute to elevating thresholds in general.
(ii) Baseline discrimination thresholds did not differ significantly between migraineurs and controls; there was a slight trend toward lower thresholds in migraineurs at both contrasts tested.