(A and B) Positions in a behavioral chamber (horizontal dimension) as a function of time (vertical dimension) of 20 Canton-S flies choosing between MCH (blue) and OCT (orange). The traces are sorted by untrained preference. Bar graphs on the right indicate population averages of decisions in favor of the left and right chamber halves before and after conditioning (pre and post), in the presence of odors (colored bars) or air (white and gray bars).
(A) Mock conditioning without electric shock preserves individual pre-training preferences.
(B) Pairing the presentation of MCH with electric shock causes conditioned avoidance of MCH.