Fig. 2. Apple cider vinegar makes females more sensitive to CO₂. Distributions of time spent in four fields of the olfactometer as in Fig. 1. (A) 0.02% CO₂ (black hatched bars) added to apple cider vinegar (vin.; grey bars; N=53, Friedman-ANOVA: P<0.001; Wilcoxon-Wilcox: P<0.001) is as attractive as apple cider vinegar alone (same data as in Fig. 1B; ns, no significant difference, Mann-Whitney U-test). (B) When all fields contain apple cider vinegar odor (grey bars) as background, a field laced with 0.02% CO₂ (hatched bars) is avoided, but only by females (N_females=29, N_males=17, Friedman-ANOVA, P<0.001; Wilcoxon-Wilcox: P<0.001). Values are means ± s.e.m.