Experimental design

Each solution was presented 4 times per session on “adapt-test” trials that were spaced one minute apart to re-establish head-space vapor concentration (Rabin and Cain 1986). Figure 3 shows the 32 experimental “adapt-test” odor pairs and corresponding 32 control pairs. They each include the 4 single-components to assess identifiability of a component presented within a mixture series. Presentation of adapt-test pairs in the same random order occurred on separate days at least one day apart for experimental and control sessions. Orders of the 4 “extra sessions” and the 2 “experimental/control” sessions were randomized across subjects. Label choices after selective adaptation in experimental sessions were compared to choices made after water (the adapting stimulus) in control sessions.

Adapt-test stimulus presentations. (A) Experimental session adapt-test pairs are shown. Each stimulus is presented as an “extra” mixture component seven times, an “ambient” mixture component 12 times and a single component after water once, shaded blue. For example, Guaiacol is “extra” in the 7 mixtures shaded yellow and “ambient” in 12 mixtures shaded green. Binary-mixture rows are tagged on the left side by black rectangles. (B) Control session adapt-test pairs mirror experimental pairs except water (W) vapor was always the adapting stimulus. Subjects were tested once on each single compound, twice on each binary mixture, 3 times on each ternary mixture, and 4 times on the quaternary mixture. Binary-mixture rows are tagged on the right side by black rectangles.