Decision strategies for the A Not-A, 2AFC and 2AFC-reminder tasks: Empirical tests

Variability of oral/taste sensitivity to fat: An investigation of attribution from detection threshold methods with repeated measurements

Accumulating psychophysical evidence suggests substantial individual variability in oral/taste sensitivity to non-esterified, long-chain fatty acids (NEFA), which is commonly referred to as fat taste or oleogustus. Recent studies have sought to determine its associations with human factors such as body mass index (BMI) and food preferences, as it has been claimed that excessive fat consumption is related to several health conditions, including obesity. Yet, the findings are controversial. On the other hand, it has been noted that considerable variability also occurs based on the methodology used to measure the fatty acid taste. Specifically, learning effects have been observed over repeated measurements of the detection threshold of NEFA, yet there has been no methodology available to take into account these learning effects. Accordingly, in the present study, a novel methodology using a descending-block dual reminder A-Not A (DR A-Not A) method with a warm-up has been proposed to measure the NEFA detection threshold based on the signal detection theory and considering NEFA taste learning effects over repeated sessions. Homogeneous subjects (young adult Korean females within the normal BMI range, non-vegetarians) were randomized to either the novel descending-block DR A-Not A method or ascending triangle method that is commonly used for fat perception studies. Pure oleic acid emulsions were used as fat taste stimuli to be discriminated from pure mineral water. Each subject completed 14 repeated visits. For the ascending triangle method, 14 thresholds were determined using a stopping rule, while for the novel method, 7 thresholds were determined each per two consecutive days, using a criterion of a lower limit of 50% confidence interval of d' = 0.5, considering the practical aspects of taste studies in food sensory science. Based on the group median results of the last two visits, the variability of the detection thresholds was reduced using the novel descending-block DR A-Not A method due to better learning effects over repeated sessions. This shows the potential of the descending-block DR A-Not A threshold method for further studies on oral/taste sensitivity to fat.

A signal detection reminder methodology to evaluate effects of odor-taste-taste interactions to enhance the perceived saltiness

Currently, numerous attempts are made to increase the perceived saltiness of food without adding more NaCl. In the present study, a method based on a reminder design and signal detection theory was used to evaluate the effects of cheddar cheese odor, meat odor, and monosodium glutamate (MSG) on the perceived saltiness and preference of three intensities of NaCl through the d' and R-Index. A solution of 2 g/L NaCl combined with odorless air was the blind reference product, which was also tested as one of the test products. The reference sample was compared to the target samples. A total of twelve right-handed subjects (19-40 years; body mass index BMI 21-32; 7 females and 5 males) performed sensory difference tasks across six days. Cheddar cheese odor was more effective in increasing the perceived saltiness and preference of NaCl solutions than meat odor. When MSG was added to the NaCl solutions, the perceived saltiness and preference were increased. Overall, the signal detection reminder method could provide a comprehensive psychophysical framework to measure saltiness perception and preference of odor-taste-taste interactions using d' (a distance measure) and R-index (an area measure).

Sensory test A-Not A rating signal detection: panel’s sensory learning and stability of decision criteria

Signal detection theory (SDT) sensory discrimination analysis using A-Not A with a two-step rating is an efficient approach to in-house sensory quality management in the food industry. For such sensory analysis using an internal panel, the panels' ability to use stable decision criteria and provide a consistent response distribution responding to "A" vs "Not A" is critical for guaranteeing the data quality. This study examined the effects of the familiarization procedure (FP) and reference presentation probability (RPP) in the SDT A-Not A rating protocol on the panels' sensory learning of samples and stability of decision criteria using SDT parameters, recognition d' (d'_Rec),criteria location (c), and discrimination d' indices. Three different protocols were compared using ice-tea samples with small differences: Control, 0.25 RPP with repeated reference tasting (FP_R); Modified-1, 0.25 RPP with reference categorization (FP_C); Modified-2, 0.5 RPP with reference categorization (FP_C). An independent sample design with three groups having equal sensitivity was used to identify the differences among the protocols. For each protocol, two sub-groups with similar decision criteria (response bias) were formed according to the results obtained from the pre-test and used for the main-test analysis. SDT analysis results indicated that the Modified-2 protocol with a higher RPP (0.5) induced the most efficient sensory learning of the reference. The protocol improved the subjects' recognition of the reference and test samples, better differentiating from the reference and stabilizing the decision criterion, resulting in higher discrimination performance (larger d'). The results showed that d'_Rec analysis, together with d' analysis using a sensory panel, is a useful tool for monitoring the panel performance and checking for the sensory data quality of the sensory difference tests. In the present paper, a detailed illustration of the A-Not A sensory test procedure and examples of how to apply the SDT indices for different business decision-making is also introduced using the design and results of the present experiment.

Investigation of human flavor perception and discrimination of the fat content in food using DR A-Not A and 3-AFC methods

This study examined human flavor perception and discrimination of powdered milk samples with various fat contents using two different sensory discrimination methods, DR A-Not A and 3-AFC. DR A-Not A was expected to be more effective. Using skim milk and whole milk powder, five different samples with various fat contents were prepared. An independent samples design was used to compare DR A-Not A and 3-AFC. Each subject performed 24 repeated tests consisting of comparisons of four different test samples from the reference sample. Signal detection d' results showed that sample discrimination was possible using DR A-Not A, but not 3-AFC. Moreover, the just noticeable difference (JND) was calculated using the results of DR A-Not A. The calculated JND was 0.47% (w/v), and the Weber fraction was 0.82. These results confirm that the DR A-Not A method is more effective for studying the human sensitivity to the fat content in food.

Hello darkness my old friend: preferences for darkness vary by neuroticism and co-occur with negative affect

Metaphors frequently link negative affect with darkness and associations of this type have been established in several experimental paradigms. Given the ubiquity and strength of these associations, people who prefer dark to light may be more prone to negative emotional experiences and symptoms. A five study investigation (total N = 605) couches these ideas in a new theoretical framework and then examines them. Across studies, 1 in 4 people preferred the perceptual concept of dark over the perceptual concept of light. These dark-preferring people scored higher in neuroticism (Studies 1 and 2) and experienced greater depressive feelings in daily life (Study 3). Moreover, dark preferences shared a robust relationship with depressive symptoms (Study 4) as well as generalised anxiety symptoms (Study 5). The results provide novel insights into negative affectivity and extend conceptual metaphor theory in a way that is capable of making individual difference predictions.

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

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.