Expression of Flavor Preference Depends on Type of Test and on Recent Drinking History

The persistence of a conditioned flavor preference was examined in 3 experiments. All contained an initial acquisition phase in which half the rats were given almond odor mixed with sucrose (AS) in some sessions and water (W) only in other sessions, whereas the other half (controls) were given explicitly unpaired exposures to almond (A) and sucrose (S) in separate sessions. Subsequent 2-bottle choice tests revealed a persistent preference for A, despite extinction exposure to A or S, but this depended on the choice offered on test: Exposure to A did not extinguish the preference for A over W but did reduce the preference for AS over S; conversely, exposure to S did not extinguish the preference for AS over S but did reduce the preference for A over W. These results indicate that flavor preferences can be resistant to extinction procedures but suggest that the expression of such preferences in choice tests depends on an adaptation-level process.