Mean cumulative licks as a function of time after first lick. Dashed lines represent ±se. Left: Rats maintained on lysine-deficient diet and given 0.1 M L-lysine for the first time first water on the home cage. Although in other experiments such rats did not demonstrate enhanced licking in a brief-access taste test in contrast to what is seen in in sodium-deficient rats presented with sodium solutions, they did significantly increase their intake of lysine after just 30 min. When 0.1 M L-lysine was pitted against 0.2 M L-threonine, noticeable preferential intake took longer. Reprinted with permission from Markison S, Thomson BL, Smith JC, Spector AC. (2000) Time course and pattern of compensatory ingestive behavioral adjustments to lysine deficiency in rats. Journal of Nutrition 130: 1320–1328.