No statistical methods were used to predetermine sample size, but our samples are similar to those generally used within the field. Data distribution was assumed normal in most cases except where sample size was n<5, in which non-parametric tests were used; equal variance was also assumed although this was not formally tested. Results are reported as mean±s.e.m. and two-sided statistical analysis was performed. Statistical significance was assessed with either parametric Student's t-test (paired or unpaired), repeated analysis of variance (ANOVA), one-way ANOVA, both with Tukey's post hoc adjustment or non-parametric Mann–Whitney U and Friedman's test with Fisher's post hoc adjustment, where appropriate. Statistical analysis was performed using SigmaPlot 10.0 (Systat Software) or SPSS 22.0 (IBM).