Induction of Scaling Errors

Abstract

Judges were required to rate the total intensity of NaCl solutions using a variety of unstructured category and line scales under a ‘rank‐rating’ protocol and a traditional protocol that did not allow retasting or the reviewing of scores. The various scales and protocols induced two types of scaling errors. The first type was named a different‐stimulus error. This involved a judge rating a stronger stimulus as equal to or less than a weaker stimulus. The second type was named a same‐stimulus error. This involved a judge giving different ratings to two stimuli of equal concentration. For all scales, judges made a higher proportion of same‐stimulus errors than different‐stimulus errors. ‘Rank‐rating’ only reduced the proportion of different‐stimulus errors. It was hypothesized that a category scale with fewer categories would induce a higher level of different‐stimulus errors but lower level of same‐stimulus errors. These trends were noted but not always significantly. For line scales, the equivalent hypotheses regarding line length were either weak or not supported. It would appear that increasing the length of a line scale is not always equivalent to increasing the number of categories in a category scale.

Optimization of a sensory evaluation protocol for measuring the umami taste

“…In previous studies, unlike this study, rank-rating showed better performance than monadic rating for intensity evaluations based on different stimulus error rates and discrimination abilities (10,13,16,17). The occurrence of errors during sensory evaluation is largely due to sensory adaptation and forgetting the taste intensity of previously tasted samples (13).…”

“…The error rate for a wrong ranking order was calculated for ranking and rating data. The error rate for a wrong ranking order refers to the rate of different-stimulus errors where a lower or equal score is given to a stronger stimulus (10). A significance level of p<0.05 was used.…”

‘Different-stimulus’ scaling errors; effects of scale length

“…Other studies confirmed this Kim & O'Mahony, 1998). Park et al (2004) designed an experiment, using both Rank-Rating and a more traditional protocol, to test both of Jeon et al's hypotheses by examining 'different-stimulus' and 'same-stimulus' scaling errors. They noted that different-stimulus scaling errors occurred more often for a category scale with fewer categories.…”

“…Jeon, O'Mahony, and Kim (2004) noted that the inappropriate assignment of scores could fall into two types, while Park, Jeon, O'Mahony, and Kim (2004) later gave them names. What they called 'same-stimulus' errors, involved giving perceptually 'identical' stimuli different scores.…”

“…They went on to argue that having eliminated the possibility of stimulus confusion and adaptation effects, scaling errors noted during the scaling procedure would be most likely due to forgetting either the intensities of prior tasted stimuli or the scores given to them. They compared a protocol that has been called Rank-Rating Kim & O'Mahony, 1998;Koo et al, 2002;Lee et al, 2001;Metcalf & Vickers, 2002;Park et al, 2004) where judges were allowed to re-taste stimuli ad-lib and also review and adjust their scores, with what will be called more traditional protocols, where such re-tasting and reviewing was not allowed. Not unexpectedly, they found that Rank-Rating, which minimized the effects of forgetting, by allowing adlib re-tasting and reviewing, resulted in fewer scaling errors than the more traditional approach.…”