2AFC Method Research Articles

Loudness and preference judgments for noises of a heat pump

An increasing number of heat pumps have recently been installed to replace conventional heating systems to provide more environmentally friendly and energy-efficient indoor heating. Most commonly, air-to-water heat pumps are chosen. However, the sounds of their fan and compressor can lead to noise complaints and can reach the limit of noise emission regulations. To achieve a more pleasant environment, research is conducted to reduce the perceived noise of heat pumps. As part of an interdisciplinary research project, this study aims to investigate the annoyance ratings of a heat pump and characterize them in terms of equivalent loudness and preference penalties. The study uses a two-alternative forced-choice (2AFC) method with a 1-up-1-down rule to measure the point of subjective equality for six stimuli representing different operation states of the investigated device. This experiment aims to identify differences between loudness and preference, and combined with an evaluation of psychoacoustic parameters, its results are used to improve the acoustics of heat pumps and the overall user experience.

Synergistic effect of combining umami substances enhances perceived saltiness

Umami substances have the potential to enhance the perception of saltiness and thus reduce sodium intake. Two sensory evaluation experiments were conducted, involving participants tasting salt solutions, and solutions with added umami substances at equal sodium concentrations. Umami substances included sodium glutamate (MSG), disodium inosinate (IMP), and the combination of them which has a synergistic effect and is a closer match to commonly-consumed foods. In Experiment 1, using the two-alternative forced-choice (2-AFC) method by 330 consumers, paired comparisons were conducted at three different sodium concentrations. The combination of MSG and IMP enhanced the perception of saltiness (p < .001 in the difference test), whereas presenting either umami substance in isolation failed to do so (p > .05 in the similarity test). Significant order effects occurred in paired comparisons. In Experiment 2, a two-sip time-intensity (TI) analysis with trained panellists verified these results and found that tasting MSG and IMP either simultaneously or successively enhanced saltiness perception at equal sodium concentrations. These findings indicate that the synergistic effect of umami substances may be the cause of saltiness enhancement, and represents a potential strategy for sodium reduction while satisfying the consumer demand for saltiness perception. Considering the application in food processing and in food pairing, umami substances can potentially be used to help to reduce salt intake in food consumption.

Evaluation omn three-forced choice audiometry for hearing threshold measurement

Common audiometry used in hospitals uses the 2AFC (Two Force Choice) method, which has a large and predictable bias. In this research, the three-force choice (3AFC) method is proposed for a smaller bias to measure hearing threshold. A hearing test was conducted on 50 participants. Three kinds of audiometric tests are used, including conventional, Pychoacoustic, and portable audiometry. A validation test was carried out by comparing the results of Pychoacoustic and portable audiometric tests using the 3AFC method with the golden standard (conventional audiometry). Pychoacoustic audiometry is unable to display the hearing threshold value in accordance with that shown by golden standard audiometry (conventional audiometry), where the mean value is 18.0–43.0, and standard deviation is 7–12 . However, the portable audiometry test is able to display a threshold value that is close to the golden standard audiometric results, with a mean value of 11—28, and standard deviation value of 3—6 . Based on the statistical calculation of the Wilcoxon test and Bonferroni's correction, it can be concluded that data collection using Pychoacoustic outdoors and Portable in the relevant room has performance that is parallel to the golden standard test (sig value &amp;gt;0.05).

The Fewer Reasons, the More You Like It! How Decision-Making Heuristics of Image Quality Estimation Exploit the Content of Subjective Experience

Imaging science has approached subjective image quality (IQ) as a perceptual phenomenon, with an emphasis on thresholds of defects. The paradigmatic design of subjective IQ estimation, the two-alternative forced-choice (2AFC) method, however, requires viewers to make decisions. We investigated decision strategies in three experiments both by asking the research participants to give reasons for their decisions and by examining the decision times. We found that typical for larger quality differences is a smaller set of subjective attributes, resulting from convergent attention toward the most salient attribute, leading to faster decisions and better accuracy. Smaller differences are characterized by divergent attention toward different attributes and an emphasis on preferential attributes instead of defects. In larger differences, attributes have sigmoidal relationships between their visibility and their occurrence in explanations. For other attributes, this relationship is more random. We also examined decision times in different attribute configurations to clarify the heuristics of IQ estimation, and we distinguished a top-down-oriented Take-the-Best heuristic and a bottom-up visual salience-based heuristic. In all experiments, heuristic one-reason decision-making endured as a prevailing strategy independent of quality difference or task.

Sensory Analysis of Different Rasasindura Samples by Two Alternative Forced Choice (2-Afc) Method

Sensory Analysis of Different Rasasindura Samples by Two Alternative Forced Choice (2-Afc) Method

An empirical evaluation of supra-threshold sensitivity measures for decremental and incremental stimulus intensity: Data from gustatory and olfactory performance

Signal detection theory provides a comprehensive psychophysical framework that enables accurate estimates of individual sensitivity for discriminating stimulus intensities (d′(t)). The present study aims to explore differences in d′ measures for decremental (d′(d)) and incremental stimulus range (d′(i)) in relation to the standard measure of d′(t). These measures were also assessed for their capabilities in segregating sensitivity groups and identifying links to body adiposity. A total of 70 healthy Caucasian males (21–39 years; BMI ranges 20.5–48.1 kg∙m−2) performed sensory difference tasks (i.e., 2AFC Method of Constant Stimuli over 10 concentrations) for 3 odours (O1-O3) and 3 tastants (T1-T3) across 6 sessions. Individual performance was used for computing d′(t), d′(d), and d′(i) for separate stimuli. Pearson’s correlations and multivariate analyses (i.e., k-means clustering, PCA varimax rotation) were applied to test for relationships across these sensitivity measures. Additionally, correlations between individual d′(t), d′(d), d′(i) versus BMI were assessed. The results revealed consistently significant positive correlations of d′(d) and d′(i) measures with d′(t) (p < 0.05). Additionally, d′(d) and d′(i) were negatively correlated for O1, T1, and T3. While d′(d) and d′(i) were able to produce low versus high sensitivity clusters, the PCA varimax rotation showed a clear separation for the gustatory and olfactory stimuli only when d′(d) was used. With regards to BMI, d′(t) and d′(i) showed negative correlations for O1, O2, and T3, whereas d′(d) yielded positive correlations for O1, and T3 (p < 0.05). Overall, these findings suggest that d′(d) represents an independent measure that could offer distinctive insights into individual chemosensory sensitivities.

Performance evaluation on three-forced choice pure tone audiometry in open space environment

In this report, we investigated the performance comparison of Three-Forced Choice (3AFC) with a pair of Bluetooth-connected active noise cancelling headphones and Two-Forced Choice (2AFC) in an audiological booth for audiometry examination. The procedure was essentially to generate mono pure tone on six different frequencies with adaptive loudness level to both left and right ear, respectively. The subject presented the pure tone, then he or she pressed a button. If it is right than the loudness level will be lowered until it is inaudible. This level was marked as the hearing threshold of the subject. We recruited 38 normal-hearing subjects who underwent to an audiology clinic for audiometry examination (using the gold standard, 2AFC technique). The recorded responses were statistically analyzed using non-parametric Wilcoxon test with Bonferroni correction. The audiometry results using the outdoor 3AFC method on 2000 Hz and 4000 Hz have mean-differences closer to ISO 226 accuracy reference for all 38 participants. These results suggested that the proposed technique may replace the gold standard.

Exploring the relationships between perceived umami intensity, umami components and electronic tongue responses in food matrices

Umami intensity promotes food flavor blending and food choice, while a universal quantification procedure is still lacking. To evaluate perceived umami intensity (PUI) in seven categories of foods, modified two-alternative forced choice (2-AFC) method with monosodium glutamate as reference was applied. Meanwhile, we explored whether equivalent umami concentration (EUC) by chemical analysis and electronic tongue (E-tongue) are applicable in PUI quantification. The results indicated that EUC was appropriate in quantifying PUI of samples from meat, dairy, vegetable and mushroom groups (r = 1.00, p < 0.05). Moreover, models with a good prediction capacity for PUI and EUC (R2 > 0.99) were established in separated food categories by back propagation neural networks, where E-tongue data were set as input. This study explored the effectiveness of the three methods in evaluating the PUIs of various foods, which provides multiple choices for the food industry.

The role of an individual's olfactory discriminability in influencing snacking and habitual energy intake

Recent studies have revealed close links between human olfaction, appetite, and food choice. However, it remains unclear whether olfactory sensitivity plays a direct role in determining food and energy intake. The present study addresses this question by assessing relationships between individual olfactory discriminability (at a suprathreshold level), snacking, and habitual energy intake. A total of 92 healthy Caucasian males (mean age = 26.1, SD = 5.8) were tested for their olfactory discriminability (measured by d′) to three food-related odorants (O1 - Vanillin, O2 – Methional, and O3 – Maltol/Furaneol mixture) with a 2-AFC method of constant stimuli. These sensory data were then analysed with two separate measures of food consumption – (1) snack energy intake within an ad libitum buffet setting; (2) habitual energy intake using four-day weighed food records. Univariate analyses of variance revealed significant results with regards to O1. Specifically, individuals with higher discriminability consumed significantly less energy from snacking as opposed to their less sensitive counterparts (p = 0.05). However, no significant relationship was found between individual olfactory discriminability and habitual energy intake. While recent years have seen increasing research focus on how external olfactory cues affect food consumption, our study offers particularly novel insights regarding the role of individual olfactory sensitivity in shaping eating behaviour.

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.

Discrimination of 2D wall textures by passive echolocation for different reflected-to-direct level difference configurations.

In this work, we study people’s ability to discriminate between different 2D textures of walls by passive listening to a pre-recorded tongue click in an auralized echolocation scenario. In addition, the impact of artificially enhancing the early reflection magnitude by 6dB and of removing the direct component while equalizing the loudness was investigated. Listening test results for different textures, ranging from a flat wall to a staircase, were assessed using a 2 Alternative-Forced-Choice (2AFC) method, in which 14 sighted, untrained participants were indicating 2 equally perceived stimuli out of 3 presented stimuli. The average performance of the listening subjects to discriminate between different textures was found to be significantly higher for walls at 5m distance, without overlap between the reflected and direct sound, compared to the same walls at 0.8m distance. Enhancing the reflections as well as removing the direct sound were found to be beneficial to differentiate textures. This finding highlights the importance of forward masking in the discrimination process. The overall texture discriminability was found to be larger for the walls reflecting with a higher spectral coloration.

Challenges to both reliability and validity of masculinity-preference measures in menstrual-cycle-effects research

Although it remains contentious, women's changeable attraction to masculine faces has been used to inform evolutionary ideas about human mating strategies. Typical experiments in this area use two-alternative-forced-choice (2afc) over a few pairs of similar images. The reliability of these measures is analysed suggesting that many studies have too few trials to be reliable. In the current experiment, fertility shifts in preferences for masculinised faces (and Africanised faces) were explored using both attractiveness ratings and a 2afc method over 80 pairs. The 2afc method showed a fertility shift in preferences whereas attractiveness ratings did not show a shift. Further, it was demonstrated how the size of the preferences shown in the 2afc tasks correlated with general face-matching performance. It is concluded that fertility is associated with improved face-processing accuracy and hence 2afc designs have poor validity as measures of masculinity preference. These issues of validity and reliability may have contributed to the contentious nature of fertility effects on preferences. Further, validity and reliability need to be considered in any study where a change in preference is identified using a comparative-preference task.

Evaluation of tablet-based methods for assessment of contrast sensitivity

Some astronauts have suffered degradation of vision during long-duration space flight, suffering from a condition that has come to be known as Spaceflight Associated Neuro-ocular Syndrome (SANS). While related morphological changes can be observed with imaging technologies such as optical coherence tomography (OCT), it may be useful to have a rapid method for functional vision assessment. In this paper, we compare three tablet-based methods for rapid assessment of contrast sensitivity. First, a relatively novel method developed expressly for touch screens, in which the subject “swipes” a frequency/contrast sweep grating to indicate the boundary between visible and invisible patterns; second, a method-of-adjustment task in which the subject adjusts the contrast of a grating patch up and down to bracket the visual threshold; and third, a traditional temporal two-alternative forced choice (2AFC) task, in which the subject is presented with a near-threshold stimulus in one of two intervals, and must report the interval containing the stimulus. The swipe method shows variability comparable to the 2AFC method, and shows good agreement in estimates of the spatial frequency of peak sensitivity. The absolute sensitivity estimated with the swipe method is higher than that of the other methods, perhaps because subjects are biased to trace outside of the visible pattern region, or perhaps due to stimulus differences.

Estimating detectability index in vivo: development and validation of an automated methodology

This study's purpose was to develop and validate a method to estimate patient-specific detectability indices directly from patients' CT images (i.e., in vivo). The method extracts noise power spectrum (NPS) and modulation transfer function (MTF) resolution properties from each patient's CT series based on previously validated techniques. These are combined with a reference task function (10-mm disk lesion with [Formula: see text] HU contrast) to estimate detectability indices for a nonprewhitening matched filter observer model. This method was applied to CT data from a previous study in which diagnostic performance of 16 readers was measured for the task of detecting subtle, hypoattenuating liver lesions ([Formula: see text]), using a two-alternative-forced-choice (2AFC) method, over six dose levels and two reconstruction algorithms. In vivo detectability indices were estimated and compared to the human readers' binary 2AFC outcomes using a generalized linear mixed-effects statistical model. The results of this modeling showed that the in vivo detectability indices were strongly related to 2AFC outcomes ([Formula: see text]). Linear comparison between human-detection accuracy and model-predicted detection accuracy (for like conditions) resulted in Pearson and Spearman correlation coefficients exceeding 0.84. These results suggest the potential utility of using in vivo estimates of a detectability index for an automated image quality tracking system that could be implemented clinically.

Effects of sulfate and nitrate on the taste of water: a study with a trained panel

The role of sulfate and nitrate in the taste of drinking water is not entirely clear. Taste threshold concentrations (TTCs) were estimated for these two species by the 3-AFC method by a trained panel, as sodium and calcium salts. In both cases TTCs for nitrate were about 100 mg NO 3 /L, twice the usual reference value of international recommendations. TTCs for sulfate were about 160 mg SO 4 /L (sodium salt) and 80 mg SO 4 /L (calcium); 75% detection values were also estimated for both anions. An experiment with a series of duo-trio tests plus preference showed that sulfate at low concentrations tended to improve the taste of water. However, at high concentrations it was perceived negatively: salty and bitter were the main descriptors used. The reversion concentration took place between 176 and 259 mg SO 4 /L. These results indicate that nitrate has to be considered an important issue for health, but with no relevant role in the taste of water. Sulfate shows a positive influence at moderate concentrations but becomes negative at high levels. The usual aesthetic-based level of 250 mg/L established by international regulations appears to be reasonable. The findings of this study with trained panellists are preliminary. Future research with consumer panels is recommended.

Olfactory threshold and odor discrimination ability in children \u2013 evaluation of a modified \u201cSniffin\u2019 Sticks\u201d test

The clinical diagnostics of olfactory dysfunction in children turns out to be challenging due to low attention span, insufficient linguistic development and lack of odor experiences. Several smell tests have been developed for adults. Most of these examinations take a relatively long time and require a high level of concentration. Therefore, the aim of the current study was to evaluate an odor discrimination and olfactory threshold test using the frequently used “Sniffin’ Sticks” in children and adolescents in a simplified two-alternative-forced-choice version (2AFC) and compare it to the original three-alternative-forced-choice test (3AFC). One-hundred-twenty-one healthy participants aged between 5 and 17 years took part in this study. Within each of the two sessions participants underwent olfactory testing using the modified 2AFC as well as the standard 3AFC method. A better test-retest reliability was achieved using the original 3AFC method compared to the modified 2AFC. This was true for the odor discrimination as well as the olfactory threshold. Age had a significant influence on both tests, which should be considered when testing young children. We discuss these findings with relation to the existing norms and recommend using the 3AFC version due to a better test-retest reliability to measure olfactory function in children.

Effect of harmonic structure of notes on categorical chord perception

This paper reports distinct differences among the harmonic structures of notes on chord perception. Experimental results clarified that the existence of harmonics greatly improved chord perception accuracy. Subjective tests were conducted for 20 combinations of three notes from a minor chord to a major chord. The fundamental notes and the highest notes were fixed. The fundamental frequency of the middle note was shifted at an equal interval on the log scale. The harmonic structure was based on saw-tooth wave. The categorical perception accuracies were compared between pure tone and complex tone including five harmonics. The fundamental notes were C5 (523.3 Hz), A5 (880 Hz), and C7 (2093 Hz). The stimuli were diotically presented at 60 dB(SPL) through electro-static headphones. The subjects were requested to answer major or minor with the 2AFC method. The categorical perception accuracy was extremely low in case of C7 without harmonics. The percent corrects were as low as 46.7% and 54.8% for Cm and C, respectively. The Cm and C percent accuracies with harmonics were as high as 77.3% and 79.5%. The Cm and C accuracies were 97.7% and 93.2% for C5. The perceived categories turned from minor to major in the region between 8th and 15th note combinations.

Optimization of a sensory evaluation protocol for measuring the umami taste

Umami substances linger in mouth for a long time, making it difficult to achieve an accurate sensory measurement. The objective was to establish a reproducible protocol to accurately measure the intensity of umami taste. Two-alternative-forced choice (2-AFC), ranking, and rating methods were compared for discrimination ability of umami taste intensities of monosodium glutamate solutions. Monadic rating and rank-rating methods were compared for accuracy in measurement of umami intensities since neither 2-AFC nor ranking method generates numerical intensity values. Mouth rinsing protocol efficiencies were investigated for 7 palate cleansing methods during umami intensity evaluation. 2-AFC was the most powerful method, followed by ranking and rating methods, for discrimination of different umami samples. Monadic rating and rank-rating methods both showed similar error rates but monadic rating was slightly more accurate than rank-rating. Crackers, a toothbrush, and water at 45oC were more effective palate cleansers than carrots and water at 18oC.

Tetrads, triads and pairs: Experiments in self-specification

Sensory difference tests can be used to investigate how well consumers can discriminate between very similar, confusable products. For this reason, it is desirable that the products are tested in a manner as similar as possible to realistic conditions of consumption. For some of these tests, it is desirable that the experimenter does not specify the nature of the difference; the consumers have to discover this for themselves. The methods generally used for this class of tests are the triangle and duo–trio. Recently, the (unspecified) tetrad method has emerged as a candidate to replace the triangle and duo–trio tests, because it is more powerful, although not as powerful as the 2-AFC and 3-AFC. Using a model and a beverage system, it was confirmed that the tetrad method was more powerful than the triangle method, despite the fact that the greater memory load of the tetrad reduced its d′ values. To initiate an investigation into more powerful tests, several self-specification protocols were developed, which differed from those used in prior investigations. These protocols successfully converted triangle tests into self-specified 3-AFCs, with a consequent increase in power. Triangle, tetrad, self-specified 2-AFC and 3-AFC methods were then compared, with the tetrad being more powerful than the triangle and the self-specified 2-AFC and 3-AFC methods being more powerful than the tetrad.

Forward displacement of expanding and contracting lines beyond their point of disappearance

It is known that a moving object that vanishes is not perceived to overshoot its endpoint. For instance, the flash-lag effect (FLE) - where a moving object appears ahead of a collocated flash - is abolished when the moving stimulus disappears with the flash. Here we show that the disappearing length of an expanding (contracting) line is perceived to be larger (smaller) than an identical flashed or continuous comparison line. In three experiments (2AFC method), dynamic vertical lines expanded or contracted to the left (right) of fixation before disappearing. On the right (left) of fixation one of the following types of static comparison line was presented: 1) flashed at termination of dynamic line, 2) continuous, offset synchronous with dynamic line, or 3) continuous, no offset. In all experiments, the size of the comparison line appeared to substantially lag the size of the dynamic line. In addition, these lags tended to be greater for contracting than for expanding lines. Results for comparison lines described in 1-3 above: 1) 91ms Expanding, 177ms Contracting; 2) 143ms Expanding, 207ms Contracting; 3) 97ms Expanding, 256ms Contracting. This is the first demonstration of dynamic stimuli with abrupt offset overshooting their endpoints, and exhibiting an effect at flash-termination. Several flash-lag accounts are grounded on the absence of an effect when both stimuli vanish together. Our results show that: a) a future trajectory is not necessary for the lag effect, and b) a flash is not necessary for forward displacement. We suggest that in nature it is inferred that disappearing objects have rapidly receded, and so their final positions are extrapolated towards an implicit vanishing point. This is supported by a larger effect in contracting motion. Expanding motion is inconsistent with disappearance and so the overshoot effect is diminished. Meeting abstract presented at VSS 2014