Determination of the Critical Flicker Fusion Frequency (CFFF) for each odorant. (A) Flies received vinegar vapor pulsed at 0.5 to 3 Hz at intervals of 0.5 Hz; for banana we tested 0.15, 0.25 and 0.5 Hz; for ethyl butyrate vapor we tested at 0.15 and 0.35 Hz. The test order was randomized and included a water vapor control. Points are means, error bars indicate SEM. (B) Critical flicker fusion frequency was defined as the highest stimulus frequency for which mean plume deviation statistically differed from the continuous plume. The critical fusion frequency was 2 Hz for vinegar, 0.5 Hz for banana, and <0.15 Hz for ethyl butyrate (t-test p < 0.05).