Licking patterns for sucrose solutions by young and aged squirrel monkeys.

The licking elicited by 0.1, 0.3, and 1.0 M sucrose solutions was measured in six young and six aged squirrel monkeys. All tongue-on and tongue-off times were recorded in addition to conventional measures of lick rate and consumption. Consummatory activity by both groups increased monotonically with sucrose concentration. Aged monkeys displayed greater within animal variability of tongue-on times than did young monkeys. Distributions of pause lengths between licking bursts contained two components, one varying inversely with sucrose concentration, the other varying inversely with age. Distributions of licks per burst contained a component that increased with sucrose concentration but none varying with age. Results indicated that licking deteriorated little with age and that consumption is controlled mainly by length and spacing of bursts, not by individual lick parameters.