Corroborcating the 2-AFC and 2-AC Thurstonian models using both a model system and sparkling water

Two experiments were conducted to investigate the suitability of the Thurstonian models for the 2-AFC (2-alternative forced choice) and 2-AC protocols (2-AFC test with a "no difference" option). The Thurstonian approach predicts that if the same subjects and products are used, the degree of difference measured between the products (d') should be the same. Experiment I tested this prediction using solutions wit:h different salt concentration. The average d' values for the 2-AFC and 2-AC were found to be 1.66 and 1.54, respectively, and were not significantly different (t-test, p = 0.46). This indicated the suitability of the models for a taste stimulus. Experiment II used a trigeminal stimulus: sparkling water with different CO2 levels as a food system. Three levels of carbonation were used and all three possible pairs of samples were compared. The d' values measured for the 2-AFC and 2-AC for each pair of products were: pair 1-1.7 and 1.7; pair 2-0.8 and 0.7; pair 3-1.2 and 1.0. For each pair of products, no significant difference was observed between the d' of each protocol (t-tests, p = 0.65, 0.20, 0.30, respectively), giving further support to the Thurstonian models of these paradigms and indicating their robustness. (C) 2003 Elsevier Ltd. All rights reserved.