PTC and PROP behave differently in tests of discrimination from their solvents

Better discrimination was possible between phenylthiocarbamide (PTC)solutions and the pure solvent when the solvent was a tasteless low-concentration NaCl solution to which the subject had adapted than when thesolvent was purified water. The reverse was true for 6-n- propylthiouracil(PROP). The differences in discrimination for PROP and PTC in the differentsolvents were caused by differences in the intensity and persistence ofaftertastes, rather than a more intense perception of the PTC and PROPtastes per se. This has consequences for traditional approaches tomeasuring taste sensitivity, as well as indicating that PTC and PROP arenot necessarily equivalent indicators of 'taster' versus 'non-taster'status.