A novel two-step rating-based 'double-faced applicability' test. Part 2: Introducing a novel measure of affect magnitude (d'_A) for profiling consumers' product usage experience based on Signal Detection Theory

Kim, I.A.,Hopkinson, A.,van Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2017 Food quality and preference Vol.59 No.-

<P>To measure consumers' product usage experience throughout the various product usage stages, a novel two-step rating-based 'double-faced applicability' test has recently been proposed by Kim et al. (2017). In this method, a 'two-step' rating (forced-choice Yes/No questions followed by 3-point sureness ratings) and 'double-faced' descriptors (a pair of semantic-differential descriptors) are used for each attribute to improve the product discriminability by reducing consumers' response bias and variations. In this paper, we introduce a novel measure that can be computed from the data from the 'double-faced applicability' test to provide a new way to generate affective product usage experience profiles. The novel measure was a nonparametric estimate of affect magnitude, named as d-prime affect magnitude (d'A), computed by considering the response ratio of positivity to negativity as the ratio of signal to noise in the context of Signal Detection Theory (SDT). The advantage of using this new measure d'A was that it meaningfully reflected the consumers' affective product usage experience for each product independently (and how this affect valence changed through a usage process), yet it can still be used to compare between products. The practical application of using d'A was demonstrated in comparison to the more conventional SDT measure d'. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Variants of A Not-A and 2AFC tests: Signal Detection Theory models

Hautus, M.J.,van Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2009 Food quality and preference Vol.20 No.3

Signal Detection Theory provides an approach to modelling difference test procedures that allows an estimate of the sensory difference between products to be obtained independently of the response bias and decision strategy used by the judge, and of the test procedure used to estimate that difference. The estimate of sensory difference obtained, d', is therefore much closer to a 'true' estimate of sensory difference than many other measures employed by sensory scientists. The methods used to generate models based on Signal Detection Theory are standard, and these methods are applied to the development of models for two test procedures (A Not-A and 2AFC) and their reminder equivalents (A Not-AR and 2AFCR). 2AFCR is procedurally identical to the duo-trio procedure with a constant reference; however, it is shown that there is more than one decision strategy available to the judge in this task.

Comparison of performance in the A-Not A, 2-AFC, and same-different tests for the flavor discrimination of margarines: The effect of cognitive decision strategies

Lee, H.S.,van Hout, D.,Hautus, M.J. Longman Scientific Technical ; Elsevier Science Pu 2007 Food quality and preference Vol.18 No.6

The performance of three different discrimination tests (A-Not A, 2-AFC, same-different) was investigated to explore the effects of varying aspects of the test protocols, such as the familiarization procedure and retasting of the reference (A), during testing on discriminability and the cognitive decision strategy used in the tests, when discriminating between the two different margarines. Seven judges, who were not familiar with margarine products, each gave 24 ratings for each of six protocols, resulting in 168 ratings in the pooled data, and from which R-indices and d' estimates were calculated. When both test products were presented beforehand for familiarization, judges adopted the beta cognitive decision strategy. When only the reference (A) was presented to the judges beforehand for familiarization, and the reference (A) was retasted before the test product either by prescription or at will, the tau cognitive decision strategy was adopted. When the number of samples tasted within a test increased, discriminability was considerably decreased. Such differences between test protocols were explained in terms of the concept formation of the test products, carry-over and fatigue effects, and memory problems caused by longer time-intervals between tastings.

Cognitive decision strategies adopted by consumers in reminder difference tests: Influence of the authenticity test

Stocks, M.,Shepherd, D.,Lee, H.S.,van Hout, D.,Hautus, M.J. Published on behalf of the Canadian Institute of F 2017 Food Research International Vol.97 No.-

<P>Discrimination tests are used in food companies to quantify small differences between products. Within the diversity of methods available, some are quicker to conduct, whereas others are more sensitive or statistically powerful. One class of methods includes the reminder tasks in which the reference product is given before tasting the actual test stimuli. During the task, such a 'reminder' can be compared directly to each test stimulus, or alternatively, only serve to prime the memory of the judge without being taken into account in decision-making. Previous research with trained judges provided evidence for the latter process while research with untrained consumers has provided some evidence for the former process. Two studies were conducted with untrained consumers using the A Not-AR and 2-AFCR reminder tasks. Objectives were to determine the decision strategies used in, and the relative sensitivity of the tasks. In addition, the use of an 'authenticity test' was explored to see if this has a positive effect on test performance. In the first study, mayonnaise and ice tea with small stimulus differences (d' < 1) were used in A Not-AR and 2-AFCR. Results were compared to those from A Not-A and 2 AFC tasks, with and without an authenticity test. It was difficult to draw clear conclusions on the decision strategy used, though the use of an authenticity test increased the sensitivity for these small differences, as it improved the performance of 6 out of 8 tests. In the second study, ice teas with larger stimulus differences (at two levels) were tested using the A Not -AR and 2-AFCR tasks, in comparison to the same-different task. The results showed that consumers use the less optimal strategies and that the authenticity test decreases performance, which is contradictory to the results of the first study. It seems that for very small stimulus differences the authenticity test can improve performance, but with larger differences the authenticity test decreases performance; it seems to confuse the judges.</P>

Consumer context-specific sensory acceptance tests: Effects of a cognitive warm-up on affective product discrimination

Kim, M.A.,Dessirier, J.M.,van Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2015 Food quality and preference Vol.41 No.-

For simple hedonic ratings, product range effects often limit the reliability and accuracy of consumer affective discriminations among multiple products. In the present study, a cognitive warm-up (CWU) procedure was applied to consumer acceptance tests in order to stabilize consumers' evaluative criteria by evoking their personal evaluation context. The effects of such procedure on the robustness of the affective product discriminations were investigated using two sets of comparison experiments, each using a related samples design. Consumers with equivalent sensory preference profile for skin lotions were screened and divided into High Reflection Thinkers (HRT) and Low Reflection Thinkers (LRT) using the Cognitive Reflection Test. They were then randomly, but evenly assigned to either a treatment (Group I) or a control (Group II) group, in which hedonic rating was performed either with or without the preceding CWU procedure, thus forming four sub-groups (treatment group-HRT, treatment group-LRT, control group-HRT, and control group-LRT subjects). For each sub-group, discriminability between the two chosen products in terms of d' value was compared across the two experimental conditions consisting of different product ranges. The results indicated that only in the control group-LRT subjects, the two conditions displayed different product discrimination. It suggests that for LRT subjects who are assumed to be more intuitive and thus might be more vulnerable to such product range effects, the CWU had a stabilizing effect on the evaluative criteria, resulting in more robust product discrimination.

Superior performance of constant-saltier-reference DTF and DTFM to same-different tests by consumers for discriminating products varying sodium contents

Choi, Y.J.,Kim, J.Y.,Christensen, R.H.B.,van-Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2014 Food quality and preference Vol.37 No.-

Reducing sodium content in foods and beverages has become very important, and great efforts are being made to achieve this while maintaining overall taste/acceptance of food. This requires more robust sensory discrimination test methods in terms of operational power because discrimination tests using food/beverages with high sodium contents might be more prone to adaptation and memory bias which might reduce the operational power of the test methods. The operational test power of six versions of the duo-trio test method (two different versions of replicated tests under three reference modes - constantly stronger-reference (S<SUB>R</SUB>) vs. balanced-reference vs. constantly weaker-reference (W<SUB>R</SUB>)) were investigated using a pair of tomato juices with different sodium content in comparison to the same-different tests using a balanced-design. The two duo-trio versions were the traditional duo-trio with a reference presented first (DTF) and the duo-trio with the reference presented both at the first and in the middle between the two alternative test samples (DTFM). An examination of the d' estimates indicated that discrimination significantly improved across all duo-trio tests and the same-different tests when using naive consumer subjects and when the sample in the first position in a test was a stronger (saltier) sample. This observation granted operational superiority to the DTF and DTFM in comparison to the same-different test, using the stronger (saltier) product as a constant-reference for discriminating products with high sodium content.

Variation of <i>d′</i> estimates in two versions of the A-Not A task

Hautus, M. J.,van Hout, D.,Lee, H.-S.,Stocks, M. A.,Shepherd, D. Wiley (Blackwell Publishing) 2018 Journal of sensory studies Vol.33 No.6

Comparative categorization method: Using 2-AFC strategy in constant-reference duo-trio for discrimination of multiple stimuli from a reference

Jeong, Y.N.,van Hout, D.,Groeneschild, C.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2017 Food quality and preference Vol.62 No.-

<P>In the fast moving consumer goods industry, unspecified (overall) sensory difference tests are commonly used with sensory panels to compare multiple types of stimuli against a gold standard. In order to measure sensory differences accurately and reliably, it is important to investigate the efficiency of unspecified sensory difference test methods not only in terms of statistical test power, but also in practice, i.e., operational test power. One unspecified difference test method, the duo-trio method using constant-reference, is procedurally equivalent to the 2-AFC with reminder (2-AFCR), for which the 2-AFC decision strategies can be used by performing a comparative categorization task. However, the feasibility and efficiency of the comparative categorization task using a constant-reference duo-trio method has not been tested for the discrimination of multiple stimuli from a reference. The objectives of the present study were 1) to evaluate the adoption of the 2-AFC decision strategy in such comparative categorization methods for discriminating multiple products from a reference, and 2) to compare the efficiency and power of these comparative categorization methods with the unspecified tetrad and balanced-reference duo-trio methods. Using two sensory panels to discriminate two different iced tea stimuli from a reference, our results confirmed that a 2-AFC strategy can be adopted in comparative categorization methods without specifying sensory attributes. With an equal number of tastings, the comparative categorization methods using a 2-AFC strategy showed comparable operational test power with the unspecified tetrad method. Among the two versions (using a constant-reference duo-trio with the reference at the first position (DTF) and duo-trio with a reference presented first and in the middle of two alternative stimuli (DTFM)) of the comparative categorization methods examined in the present study, DTF was more reliable across repeated sessions than other unspecified methods investigated.</P>

Higher performance of constant-reference duo-trio test incorporating affective reference framing in comparison with triangle test

Kim, M.A.,Chae, J.E.,van Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2014 Food quality and preference Vol.32 No.1

For measuring the sensory discriminability of consumers, ways to optimize the test protocols were investigated in relation to the concept of the test practicality and operational power. Specifically, reference frames using consumers' affective state of mind and adoption of selective tasting orders of products in a test were designed as the operationally more powerful ways of using consumer discrimination tests. Their effects were investigated in terms of three different versions of the constant-reference duo-trio tests, in comparison to the balanced-reference triangle test as a control protocol. The three different duo-trio protocols were: (1) a duo-trio with a constant-reference of a stronger sample; (2) a duo-trio with a constant-reference of a stronger sample with a fake brand name provided and (3) a duo-trio with a constant-reference of each subject's preferred sample. Based on signal detection analysis assuming a comparison of distances strategy, all three duo-trio tests were determined to be superior to the triangle test when the first two replications were compared, while only the duo-trio test using the affective reference frame (either with the brand name encoded or with the preferred reference), were found to be superior to the triangle test when all replications were compared. Significant sequence effects were found only for the triangle test. These results indicated that the duo-trio with a constant-reference incorporating the consumers' state of mind by using the affective reference frames and selective test sequences had the operationally favorable sample sequences and higher test practicality.

A novel two-step rating-based 'double-faced applicability' test. Part 1: Its performance in sample discrimination in comparison to simple one-step applicability rating

Kim, I.A.,Hopkinson, A.,van Hout, D.,Lee, H.S. Longman Scientific Technical ; Elsevier Science Pu 2017 Food quality and preference Vol.56 No.1

<P>Due to its simplicity and efficiency for evaluating product attributes, check-all-that-apply (CATA) questions have been widely used. Yet, CATA questions have been reported to lack discriminability of subtle product differences and suffer from the problems of response bias from satisficing and acquiescence behaviors. In the present paper, a novel two-step rating-based 'double-faced applicability' test was developed as an extended response format of CATA, to improve its sensitivity for product discrimination and for stabilizing subjects' evaluative criteria. In the 'double-faced applicability' test, each attribute was 'double-faced', meaning that two descriptors (a pair of semantic-differential descriptors) are separately presented in the questionnaires representing both sides of each attribute. For performing the two-step rating on each attribute in the questionnaire, subjects are instructed to first respond 'Yes (does apply)' or 'No (does not apply)' and then to answer a 3-point sureness rating (how sure they were about their Yes or No response). The performance of the two-step ratings in this new method was compared to a simple one-step applicability rating test method as well as the forced-choice Yes/No questions without the sureness rating in terms of sensitivity in sample discrimination. The results showed that the 'double-faced applicability' test provided better product discrimination and showed the potential to reduce acquiescence response bias when using existing variants of CATA response formats. (C) 2016 Elsevier Ltd. All rights reserved.</P>