ROC curve analysis to determine effects of repetition on the criteria for same-different and A Not-A tests

Judges performed over 2000 same-different tests followed by over 2000 A Not-A tests, to distinguish between ‘threshold’ sodium chloride solutions and purified water. Fitting ROC curves to the data indicated that three out of four judges used a τ-strategy for the same-different test. The hypothesis that judges might, with experience, start to categorize the stimuli and switch to a β-strategy was generally not confirmed. On changing to the A Not-A method, half the judges appeared to continue initially to use the τ-strategy. The hypothesis that judges might make comparisons with the preceding stimulus rather than the standard stimulus, because of prior extensive experience with the same-different test, was generally not confirmed. Yet, in all cases there were exceptions.     

Affective discrimination methodology: Determination and use of a consumer-relevant sensory difference for food quality maintenance

To achieve more efficient decision making for many business objectives including reformulations and processing changes in the food industry, the important questions become 1) what is the best way to measure consumer discrimination and 2) how much discrimination is meaningful in consumer preference that can be used as a business action standard for food quality maintenance. The purpose of the present paper was to develop a consumer sensory discrimination methodology using affective reference framing to provide more accurate information on both questions. For such affective methods, two versions of repeated duo–trio tests using the preferred sample as reference were implemented: Affective group I—each of 8 repeated duo–trio tests was preceded by a paired-preference test; and Affective group II—a paired-preference test was performed before each of the two sub-sessions consisted of 6 repeated duo–trio tests and the preferred sample was used as a constant-reference during the sub-session. The discrimination performance of these tests was compared to the analytical balanced-reference duo–trio test. Results indicated that for affective group I only, it was possible to identify the ‘affective discriminators’ who showed genuine preference for one product over another and their sensory discrimination in the affective method was significantly higher than in the analytical method. It suggested that this affective method is a desirable consumer sensory methodology that can reveal insightful consumer-relevant sensory differences by comparing sensory discriminations between the so-called ‘affective discriminators’ and ‘affective non-discriminators’.     

Quantification of Sensory and Food Quality: The R-Index Analysis

ABSTRACT:  The accurate quantification of sensory difference/similarity between foods, as well as consumer acceptance/preference and concepts, is greatly needed to optimize and maintain food quality. The R-Index is one class of measures of the degree of difference/similarity, and was originally developed for sensory difference tests for food quality control, product development, and so on. The index is based on signal detection theory and is free of the response bias that can invalidate difference testing protocols, including categorization and same-different and A-Not A tests. It is also a nonparametric analysis, making no assumptions about sensory distributions, and is simple to compute and understand. The R-Index is also flexible in its application. Methods based on R-Index analysis have been used as detection and sensory difference tests, as simple alternatives to hedonic scaling, and for the measurement of consumer concepts. This review indicates the various computational strategies for the R-Index and its practical applications to consumer and sensory measurements in food science.     

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

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.     

Observed discriminability is more variable than predicted by signal detection theory

Food scientists and technologists are interested in how sensitive judges and consumers are to changes in product formulations. Numerous approaches to measuring sensitivity have developed at a rapid rate in the last 25 years, however, the evaluation and assessment of sensory tasks is still ongoing. The current study compared the efficiency of four difference tests (A-Not A, A-Not AR, 2-AFC, 2-AFCR) across three concentrations (difficulty levels) of orange essence. To determine which of the four tasks had the lowest variance in d′, the decision strategy used by the judges first had to be ascertained. Using the rating-scale approach of signal detection theory, four estimates of sensitivity, d′, were obtained for each judge (n = 10) at each of the three difficulty levels, for all four tasks. Results indicate that the majority of judges adopted the β-strategy for the A-Not A and A-Not AR tasks, and the β/τ-strategy for the 2-AFC and 2-AFCR tasks. The A-Not A and A-Not AR tasks produced greater estimates of d′ than the other two tasks, and the A-Not A task exhibited a greater variance in d′ than the other three tasks.     

Perception of Texture by Trained and Consumer Panelists

Four experiments were conducted to assess the relationships between judgments of the perceived texture of foods by trained and consumer panelists. In Experiment 1, no differences were observed between trained texture profile panelists and naive consumers in a similarities scaling task. In Experiments 2 and 3, good linear correlations were observed between scalar judgments of texture, although a broader perceptual range was evidenced for trained panelists. In Experiment 4, psychophysical exponents of texture were found to be larger for trained than for consumer panelists, and judgments of acceptability also differed between the two groups. It was concluded that, through experience, trained texture profile panelists develop a broader perceptual range of textures, but that regression equations can be developed to relate these data to consumer data.     

Supplementing hedonic and sensory consumer research on beer with cognitive and emotional measures,and additional insights via consumer segmentation

A consumer-based multivariate approach to the study of eight commercial beers (mass-produced, speciality and craft) was undertaken in New Zealand with ∼200 people. The beers spanned a wide range of sensory characteristics, from traditional lager and ale styles to high flavour impact beers with novel flavours (e.g. liquorice and rosemary) and less common styles (weisse and gose). These flavour differences were a larger driver of consumers’ hedonic/emotional/cognitive responses than alcohol content, which ranged from 0.5 to 7.2% alcohol by volume (ABV). The supplementation of hedonic and perceptual measures with emotional and cognitive variables resulted in a more detailed differentiation of products, which was further enhanced by consumer segmentation. In the rapidly evolving beer market, there is significant value in product-focused consumer research that delivers insights “beyond liking” and provide a deeper level of understanding about consumers’ product experiences. The research also contributed methodologically to the multivariate approach by considering pros and cons of study implementation aspects such as free-listing and ballot length. This will benefit future researchers in study planning and execution.     

Feelings as a basis for discrimination: Comparison of a modified authenticity test with the same–different test for slightly different types of milk

An analytical sensory test and an authenticity test were used to evaluate subtle flavour differences in milk. Consumers who habitually drink milk were selected for the tests. These consumers, we assume, possess implicitly learned knowledge about the taste of milk. In the authenticity test the consumers were able to differentiate milk samples which they were less able to discriminate in the analytical test. These results indicate that the consumers’ ability to perceive subtle flavour differences is sharpened in this test as compared to the analytical test. The two tests are compared using d′-values, for which a novel calculation is suggested for the authenticity test.     

Analysing relations between specific and total liking scores

The objective of this article is to present a new statistical approach for the study of consumer liking. Total liking data are extended by incorporating liking for specific sensory properties. The approach combines different analyses for the purpose of investigating the most important aspects of liking and indicating which products are similarly or differently perceived by which consumers. A method based on the differences between total liking and the specific liking variables is proposed for studying both relative differences among products and individual consumer differences. Segmentation is also tested out in order to distinguish consumers with the strongest differences in their liking values. The approach is illustrated by a case study, based on cheese data. In the consumer test consumers were asked to evaluate their total liking, the liking for texture and the liking for odour/taste.     

Paired preference tests: ‘Liking’, ‘Buying’ and ‘Take Away’ preferences

Paired preference tests of liking require consumers to specify which of two foods are preferred or whether there is no preference. For ‘Buying’ preference tests, consumers specify which of two foods they are more likely to buy or whether there is no operational difference in likelihood to buy. The former test is designed to predict choice behaviour, the latter, buying behaviour. To validate the predictive ability of such tests, consumer choice and buying behaviour should be observed for several months. Another approach is to allow consumers to take away some of the foods used in the test and observe what they take. Consumers of potato chips were required to taste chips whose flavour and appearance were obviously different. A first group (N = 109) were given a traditional paired preference test of liking. A second group (N = 108) were given a preference test of buying. A third group (N = 101) were given both tests. After the test, out of sight of the experimenter, consumers were presented with two rows of plain plastic ‘snack’ bags, filled with the chips used in the test. They could take away either two bags of the same type of chip (a ‘Take Away’ preference) or one of each type (no ‘Take Away’ preference) or take neither (rejection). ‘Liking’ preferences predicted what was taken away for only 48% of consumers for the first group and 45% (third group). For ‘Buying’ preferences, the correspondence was 56% (second group) and 60% (third group). Using buying tests separately or together with liking produced some differences. More reliably, approximately 60% of consumers in all groups chose one bag of each. ‘Take Away’ preferences suggested low predictability for paired preference tests of liking and buying. ‘Take Away’ preferences are not a substitute for following a consumer for several months but they are a step in the right direction.     

A comparison between nine laboratories performing triangle tests

Fifteen groups of participants in nine laboratories performed triangle tests with two pairs of soft drinks. Groups differed in practice level with triangle tests: eight groups of 60 consumers who were not used to triangle test, three groups of qualified assessors who have already performed a few triangle tests, and four groups of trained assessors with a more extensive practice of triangle tests; qualified and trained groups included 9 or 18 assessors. The soft drinks were made from syrups at two levels of dilution in order to achieve about 55% of correct responses to test for difference and about 40% of correct responses to test for similarity. Participants performed three replicated tests with each pair of drinks, except the groups of 9 assessors who performed six replicated tests. When testing for difference, large inter-groups differences were observed. One consumer group and one trained group from two different laboratories failed by far to reach the critical number of correct responses leading to demonstrate a significant difference between products. For similarity test, all consumer groups demonstrated a significant similarity whereas two qualified groups and one trained group did not. This is explained by a slightly higher level of performance for qualified and trained assessors compared to consumers.     

Consumer acceptability of coffee as affected by situational conditions and involvement

For understanding consumer behaviors more closely to what would be observed in real-life, “situational” tests has been widely studied using two main approaches: ‘physical environment’ or ‘cognitive evocation’. Both approaches have shown advantages in adopting consumption context in consumer tests. However, it has not been investigated whether either one of the approaches may be more effective or whether using these approaches together would be more advantageous than using each solely in terms of bring in consumption context. The aims were to understand the effects of evocation in different environmental settings on consumers liking and to explore the differences of these effects based on consumer involvement levels. Consumers participated in one of the 4 contextual conditions of 2 × 2 factorial design, consisting of ‘evocation’ factor (with vs. without evocation instruction) and ‘environment’ factor (booth vs. simulated café), respectively. Consumers evaluated liking for two coffee samples and responded to a coffee involvement questionnaire. The results showed that both factors have influenced on consumer liking. These effects were different according to coffee types differing in hedonic levels. Vividness of evocation lasted longer in the simulated café setting, implying physical cues reinforcing cognitive evocation. When consumers were classified according to involvement scores, liking score of the high involvement group was little affected by either situational factors, while low involvement group was highly affected by the ‘environment’ factor. The findings of the study provide important perspectives to be considered for researches into “situational” tests, including which situational approach to apply as well as consumer involvement.     

The evolution of a model: A review of Thurstonian and conditional stimulus effects on difference testing

The application of Thurstonian modeling to difference tests is reviewed and explained non-mathematically. How experimental variables can affect the variance of perceptual distributions and reduce discriminability (d′ values) is described. The tendency of triangle and 3-AFC tests with one stronger stimulus and two weaker stimuli to be more sensitive than triads with one weaker and two stronger stimuli, is explained using the idea of conditional stimuli. From this, the development of sequential sensitivity analysis and the four distribution Thurstonian model is described. These ideas are then developed further to produce a potential eight distribution conditional stimulus model, to account for the effects of various interstimulus rinses and cognitive contrast. Also, the physical and physiological properties of the salt taste detection system, used in the development of these models, are outlined.     

Liking patterns moderate the relationship between sensory,emotional and context appropriateness profiles: Evidences from a Global Profile study on alcoholic cocktails

This study aimed to further the development and application of the Global profile approach, by (1) extending it to another product category, alcoholic cocktails; (2) investigating the relationship between sensory-emotions-context appropriateness in consumers differing for liking patterns; and (3) integrating the approach beyond product differentiation to consumer differentiation, thus improving and gaining a further insight into differences among consumers (consumer characterization). This was done taking into account consumer differences in oral responsiveness, personality traits, familiarity, explicit responses to products and implicit attitudes towards brand.Six alcoholic bitter-based cocktail samples were rated for liking, sensory properties, emotions and context appropriateness. Three clusters with different liking patterns for alcoholic cocktails were identified: ‘Fruit-bitter lovers’, ‘New-bitter lovers’ and ‘Classic-bitter lovers. Very small differences in sensory evaluation were found between the three clusters, while instead large differences were found for emotions and, to a lesser extent, for context appropriateness. Furthermore, the relationships among emotions, contexts and sensory properties were different in the three clusters.Clusters differed partly by gender, personality traits and alcohol consumption. A higher percentage of females was found in ‘Fruit-bitter lovers’; these consumers were also characterized by a higher Behavioral Inhibition System (BIS) scores and a lower level of alcohol consumption. ‘New-bitter lovers’ liked cocktails with very different sensory characteristics who were associated with specific contexts of consumption. These consumers were less involved with cocktails than the other clusters. ‘Classic-bitter lovers’ cluster liked a broader variety of cocktails and also showed a more implicit positive attitude towards the bitter ingredient brand and a higher familiarity for cocktails in general. The information collected through this multidimensional approach will allow a better understanding of the differences in liking patterns among different groups of cocktail consumers and may be used to improve strategies for product innovation and consumer targeting.     

Consumer acceptance measurement focusing on a specified sensory attribute of products: Can the attribute-specified degree of satisfaction-difference (DOSD) method replace hedonic scaling?

A specific attribute can play an important role in determining consumers’ perceived quality and acceptance of a product. Kim, van Hout, Dessirier, and Lee (2018) proposed a new affective method, the degree of satisfaction-difference (DOSD) method, to study consumer acceptance in terms of overall satisfaction with products. In the present study, this DOSD method was further developed to assess satisfaction for a specified attribute of products rather than overall satisfaction, and this modification is referred to as the attribute-specified DOSD method. To test its applicability, 11 bouillon products (including a reference product) varying in viscosity were used as stimuli. Satisfaction with the perceived mouthfeel thickness, which is a viscosity-related sensory attribute, was evaluated with the attribute-specified DOSD method and with a 10-point category scale for overall liking as the control method. Two groups of consumers performed either the attribute-specified DOSD method or hedonic scaling over two repeated sessions. Results showed that the satisfaction patterns of the attribute-specified DOSD method were similar to those of the hedonic scaling across products, confirming that the mouthfeel thickness was a determinant of consumer acceptance for bouillon products. Examining the test reliability in terms of consistency of consumers’ responses for the same stimulus in different sessions, both groups showed consistent results. The subjects who performed the attribute-specified DOSD method were also segmented based on the degree of satisfaction with the reference product. Here, each consumer sensory segment showed different patterns on satisfaction with other test products. These findings demonstrate the potential of the attribute-specified DOSD method for measuring the consumer responses to the level/quality of an important attribute/dimension and highlight its usefulness for consumer sensory segmentation.