Reviewed by: Ranier Gutierrez, Centro de Investigación y de Estudios

Behavioral and electrophysiological studies suggest that rats can identify a taste stimulus with a single lick, in <200ms. However, the conditions under which these conclusions were drawn varied widely across experiments. We designed a series of experiments to assess the effects of the number of licks of a tastant that are available, tastant concentration and prior learning experience on the speed with which a tastant can modify behavior. To accomplish this we tested exemplars of four basic taste qualities (quinine, 0.1mM; NaCl, 100mM; saccharin, 4mM, or sucrose, 100mM; citric acid, 10mM) in rats that were conditioned to avoid quinine. Taste stimuli were available for one, two, or three licks on separate days. All tastants were presented in a randomized order interspersed with water rinse licks presented on a variable ratio schedule. A tastant-specific significant increase in the proportion of long pauses in licking following quinine presentation was defined as evidence of “behavioral identification. ” Rats with aversion training given three licks of all taste stimuli paused significantly more often after quinine by the fourth interlick interval, ∼580ms. Control rats showed no evidence of quinine (0.1mM) identification. When rats in all conditioning groups were tested with a high concentration of quinin