A technique previously unreported in the food sciences literature, the Single-Interval Adjustment Matrix (SIAM) Yes-No task, works by controlling the taster's response criterion, with the goal of producing a bias-free estimate of the absolute threshold. Absolute thresholds were estimated for sucrose in aqueous solution using the SIAM Yes-No task. Obtained estimates were similar to those reported in the literature. These estimated threshold concentrations were then used with the same tasters in a two-alternative forced-choice task. The performance of the tasters was consistent with a 75% definition of threshold for this task. In terms of speed, the SIAM Yes-No task performed well. These results suggest that the SIAM Yes-No task is a useful choice in the measurement of absolute thresholds for gustatory stimuli. PRACTICAL APPLICATIONSRecipe changes or ingredient substitutions introduce challenges for food and beverage manufacturers. Having made changes, it is crucial that sensory and affective tests be undertaken to ensure the product remains in favor with consumers. In regards to sensory testing a common measure employed by food scientists is the absolute threshold. However, given the difficulties inherent in sensory testing there is a need for sensory methods that minimize stimulus presentations while maintaining measurement validity. The SIAM Yes-No task, a technique hitherto unreported in the sensory sciences literature, 3 Corresponding Journal of Sensory Studies 25 (2010) 940-955.

The SIAM yes-no task is an efficient bias-free adaptive procedure for estimating absolute thresholds, though it arguably requires further evaluation prior to its adoption into mainstream psychological research. We report two experiments undertaken in the auditory and gustatory modalities designed to assess the accuracy and efficiency of the SIAM method. In the first experiment, estimates of absolute thresholds for 1000-Hz tones obtained using a two-alternative forced choice adaptive procedure were compared to those obtained using both the SIAM yes-no task and a modification of the SIAM task incorporating the method of free response, the SIAM-rapid. In Experiment 2, we compared absolute thresholds for sucrose in solution obtained with either a two-alternative forced choice adaptive procedure or the SIAM yes-no task. Both experiments demonstrated the efficiency and validity of the SIAM approach, with SIAM thresholds proving to be equivalent to those obtained in the two-alternative forced choice tasks and to those reported in the literature.

Four sensory difference tests -A-Not A, two-alternative forced choice (2-AFC) and their reminder counterparts, A-Not A with reminder task (A-Not AR) and 2-AFC with reminder task (2-AFCR) -were applied to pairs of aqueous solutions containing different concentrations of citric acid to determine the decision strategy adopted by judges in the reminder tasks, and which of the four tasks has the greatest test sensitivity. Three solution types, each containing a different number of compounds, were employed to determine if the strategy adopted or test sensitivity is contingent upon the number of compounds in solution. Auditory and visual research suggests that observers adopt a tau (t) strategy for simple stimuli (which could be likened to a solution containing a few compounds) and a beta (b) strategy for complex stimuli (which could be likened to a solution containing several compounds). Results suggest that the strategy adopted for the 2-AFCR task is fairly consistent across judges and solution types, whereas that for A-Not AR is fairly consistent across judges but depends on solution type. All four tasks were found to have similar test sensitivity. The results highlight the need for caution when using difference tests when the decision strategy being used by judges is not known. Relatively large errors in estimates of performance can result from an incorrect assumption. PRACTICAL APPLICATIONSChanges to ingredients, processing and storage methods frequently challenge manufacturers who strive to maintain products that will appeal to consumers. Difference tests can assist the manufacturer in determining the effect of such changes on perception. Difference tests need to be effective in use and must produce valid and reliable results. A-Not A and 2-AFC tasks are sensitive to sensory differences, and are frequently used, but require a time-consuming familiarization procedure. A-Not AR and 2-AFCR do not require this, as they provide a comparative reminder stimulus on each trial. Comparisons of these four tasks showed all to be equal in test sensitivity, a component of validity, however, not equal in reliability. Of the reminder tasks, A-Not AR was less reliable, as decision strategy depended on stimulus type, whereas in 2-AFCR, decision strategy was more consistent, particularly for stimuli containing more components.

No abstract

No abstract