Consummatory Contrast Effects in Nondeprived Rats Following Shifts in Sucrose Concentration

Successive positive and negative contrast effects in consummatory behavior were investigated following shifts in sucrose concentrations in nondeprived subjects. Forty-four male albino rats were given daily 5-min access to either a 4%- or 32%-sucrose solution across a 14-day preshift period. Subjects in each group were then assigned to either a control or shifted condition. Shifted groups were upshifted (4–32%) or downshifted (32–4%) for a 10-day postshift period. Negative contrast was apparent in both lick rate and time spent at the drinking tube across the first 4 days of postshift. Positive contrast effects were not obtained, but rather a significant effect opposite to positive contrast occurred. The improbability of the ceiling effect explanation for the present results is discussed. Differences relative to deprivation state and the role of perceptual (taste) factors in contrast effects are also examined.