International Journal of Comparative Psychology

Previous studies of autoshaping of drinking report a positive relationship between experience with autoshaping procedures and drinking, but this effect was confounded with age, as the rats were older when they drank more. The present experiment evaluated the effects of the age of male Long-Evans hooded rats [90-days old (Younger group) vs. 135 days old (Older group)], at the beginning of the study, on drinking induced by Pavlovian autoshaping procedures. Autoshaping procedures consisted of pairings of sipper conditioned stimulus (CS) with food unconditioned stimulus (US). Rats were deprived of neither food or fluid, and sweeteners were not employed at any time during the study. For all rats (n = 32), during sessions 1-10, the sipper CS contained water. Thereafter, for rats in the Ethanol groups (n = 20), the sipper CS contained ethanol, with the concentration (1, 2, 3, 4, 5, 6%, v/v) increasing across autoshaping sessions. For rats in the Water groups (n = 12), throughout the experiment the sipper CS contained tap water (0% ethanol). Rats in the Younger group drank more ethanol and more water from the sipper CS than rats in the Older group, and across age groups there was more ethanol drinking than water drinking, an effect unlikely due to foraging for calories. Data support the hypothesis that ethanol’s pharmacological effect was to enhance autoshaping, resulting in a positive feedback loop inducing still more ethanol drinking. The younger rats were more vulnerable to autoshaping effects. Implications for models of addiction are discussed.