Figure 4.

Retronasal relative response efficacy correlates with the volatility of the odorants. A–E, The mean r/o response ratio of Figure 3A for each odorant is plotted against vapor pressure (VP, mmHg; A), partition coefficient [P(logK_ow); B], density (g/ml; C), boiling point (bp, °C; D), and polar surface area (Ų; E). Note that the r/o ratio correlates significantly with vapor pressure (r = 0.92, p < 0.005), density (r = −0.80, p < 0.05), and boiling point (r = −0.93, p < 0.005), but not with the partition coefficient or polar surface.