The day after the head dipping assessment, mice were placed back onto the same hole-board apparatus for a second 10-min test. Two small objects (centrifuge caps, black binder clips, or marbles; all objects ≈1.5 cm across) were placed into two of the holes at opposite corners. Preference was calculated as the amount of time spent head dipping in holes that had objects divided by the total time spent head dipping (percent preference). Activity was recorded as the number of beam breaks.
