Reciprocal training was performed to ensure that inherent preference for either odor did not affect conditioning. Training consisted of 3 repetitions (spaced by 50 min) of 10 min of odor 1, then 10 min odor 2 plus ethanol. A separate group of flies was simultaneously trained with 10 min odor 2, then 10 min odor 1 plus ethanol. Vials of flies from Group 1 and Group 2 were paired according to placement in the training chamber and tested simultaneously.
