He claimed to have learned the 4 possible sensation changes induced by the stimulus pairs and was categorizing these. Yet, the results of Lee and others a were not a rare exception. Chae and others , using milk stimuli, had consumers perform same—different tests after performing prior familiarization procedures to vary their state of mind. For this, 1 group used rank-rating to evaluate samples for liking and other integrated semantic attributes like freshness, well-being, and off-flavor. This was to cause them to perform the same—different test under an affective and hedonic state of mind, which was hypothesized to approximate more towards realistic conditions of consumption.
A 2nd group used a familiarization procedure to put them in a more analytic state of mind, with rank-rate for similarity to a reference standard. Next, consider the A Not—A test which was described by Peryam It also has no fixed protocol.
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Then a series of comparison stimuli are presented to the judge in random order. Some are the same as the standard A , while others are the stimuli to be discriminated from the standard Not-A. Judges are required to categorize which are which. For these protocols, once judges have started tasting the comparison stimuli, the standard s cannot be retasted.
Yet, Peryam and Pfaffmann suggested that the standard might be retasted occasionally as a reminder. Versions of most of these protocols are described in standard texts for example, Amerine and others ; A. In this case, it would be modeled in the same way as the same—different test. Reminders would be seen as the opportunity of retasting the standard so that subsequent comparisons could be compared to the fresh memory of the reminder.
The A Not—AR would merely be a succession of same—different tests. Santosa and others required judges to perform A Not—A tests immediately after performing over same—different tests described previously. Regarding the effects of prior same—different testing, all judges reported that at first, their cognitive strategy for the A Not—A test was affected by the prior same—different tests.
They reported that instead of comparing the 5 comparison stimuli with the standard, they compared them with the immediately preceding stimulus. Yet, this did not show up in the ROC data, except for 1 judge. After that, he switched mostly but not always to comparisons with the standard. Yet, this was slight evidence for a strategy whereby initially the comparison stimuli were not compared to the standard stimulus but to immediately preceding stimuli.
The 2nd way of conceptualizing the A Not—A method is quite different. Hautus and others , conceptualize it as equivalent to the signal detection Yes—No procedure, which also uses single presentations of stimuli. For example, using the Yes—No procedure, a judge might be reporting whether for single presentations, the tongue is experiencing a taste or not O'Mahony a , b.
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The reminder is not conceptualized as a stimulus for comparison as in a same—different test. They go on to explain that in this case, estimated performance would be reduced by a factor of. Why are there contradictory ways of conceptualizing the A Not—A method? It would seem to depend on assumptions about which memory exemplars the comparison stimuli are being referred to. For the Yes—No procedure, it is assumed that judgments are made relative to firmly established stable exemplars embedded in the memory.
They are not made relative to fading and distorting temporary exemplars generated by some prior tasted stimuli. For example, in a detection experiment when a judge decides whether the tongue is experiencing a taste or not O'Mahony a , b the exemplars for the presence of a taste or its absence are firmly established and embedded in the long-term memory. Yet, they are experimental questions and once again the ROC curve becomes a useful tool. Lee and others b compared performance on A Not—A tests with ranking.
Using 6 margarine products, panelists experienced with margarine tasting, performed a ranking test and the A Not—A test, using 2 protocols. For the 1st protocol, only a single standard A was presented beforehand, although it could be retasted as a reminder during testing as often as desired.
R-Index values, equivalent to the proportion of area under the ROC curve Brown ; O'Mahony , ; Lee and van Hout were calculated as measures of performance. Ranking gave higher R-Index values than either version of the A Not—A test, probably due to the forced choice nature of the task with a consequent elimination of boundary variance. The A Not—A, the protocol, where all samples were presented as standards beforehand, elicited the better performance of the two.
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This would have produced better performance. They entertained a further possibility. The judges were panelists who were familiar with margarine testing. Their experience on margarine panels ranged 5 to 12 y. For some of the judges, the difference in R-Index values between the 2 A Not—A protocols was comparatively small.
It is possible that they already had a set of exemplars in their memory, some of which might have been relevant to the A Not—A tests at hand. Yet, Lee and others c reexamined the A Not—A test using only 2 margarine products and judges who were not experienced with margarine.
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For all A Not—A tests, judges responded with sureness ratings for each comparison stimulus. They used 2-AFC tests where beforehand the 2 stimuli were presented for familiarization and then presented as a series of 2-AFC tests. After each 2-AFC, the individual stimuli were given sureness ratings.
For a second 2-AFC, 2-AFC reminder just 1 stimulus was given as a standard beforehand for familiarization and pairs of samples were presented for 2-AFC tests, followed by sureness rating for each stimulus, as previously mentioned. Finally, judges were given same—different tests short version also with sureness ratings.
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Both stimuli were presented beforehand for familiarization followed by the same—different test; sureness ratings were not used. From these, the cognitive strategies used in each protocol were surmised. For the A Not—A test where both standards were presented beforehand, R-Indices were higher than when only one standard was presented. Yet, the researchers reported that in the A Not—A voluntary reminder test, judges tended to taste the reminders more than in the A Not—AR. Judges would then have had to resort to comparisons with the single standard and reminders.
The more frequent the reminders, the better the performance. This suggested that the judges were tending not to use the reminder stimuli as mere reminders but rather as standards for comparison. For the A Not—A with voluntary reminders, the protocol has not yet been effectively modeled. The researchers suggested that the task was difficult because of the increased memory load. An alternative explanation is that the judges were not comparing the 2 stimuli relative to each other, as is required in the 2-AFC, but instead they were comparing them in terms of their similarity to the reminder stimulus.
It can be argued that presentation of only a single standard would encourage this. It would then seem that they were performing duo—trio tests. This is rather high, suggesting that not all judges were using a duo—trio. The final 2 experiments previously mentioned were interesting first looks at the various versions of the A Not—A tests. Some results were expected and some were a surprise. They suggest that the protocols with one standard A presented prior to the comparison stimuli might need to be treated as entirely different from protocols where 2 or more A, Not-A standards are presented. They also encourage some opposing assumptions.
Further research is needed and the ROC curve, either by its shape or by the proportion of area beneath it R-Index will continue to prove a useful tool in such investigations. Previously, this had been the domain of psychophysicists, often with visual or auditory stimuli. Yet, Food Sensory Scientists, using ROC curves to investigate cognitive strategies with taste or food stimuli, have produced some surprising results.
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The surprises may be due to the fact that most prior experiments come from the discipline of psychology using visual or auditory stimuli. Performing with these, judges can be envisioned as very highly experienced experts, having concentrated on them and communicated about them for most of their life. This is rarely true for taste and food stimuli. Unlike many other species, we rely mainly on vision and are not primarily guided by the chemical senses. Yet, these were seen as exceptions. The picture for the various protocols of the A Not—A strategy is becoming established but needs more research.
Is it a short-lived exemplar elicited by tasting a prior standard? On the other hand, is it a relatively permanent exemplar which can be called upon once the experiment has ceased? This is worthy of investigation because it affects the choice of the cognitive strategy? Is the thoroughness of inspection when 2 standards are presented prior to the comparison stimuli, an important variable?