JND of gustatory and olfactory stimuli
•
1 like•356 views
My MSc thesis presentation on just-noticeable-differences of gustatory and olfactory stimuli.
Recommended
More Related Content
Viewers also liked
Viewers also liked (13)
Similar to JND of gustatory and olfactory stimuli
Similar to JND of gustatory and olfactory stimuli (15)
Recently uploaded
Recently uploaded (20)
JND of gustatory and olfactory stimuli
- 1. Just-Noticeable Differences of gustatory and olfactory stimuli Georgia Karyotaki MSc student Sensory Science and Eating Behaviour group Division of Human Nutrition prof.dr.ir. K. de Graaf dr. S. Boesveldt
- 2. Background • Taste perception • Taste: nutrient-sensor (e.g. bitterness/sweetness) • Need for identifying these food sources even in low concentrations • Tiny differences of concentrations should be detected • Smell perception • Synthetic, multidimensional, experience-based Discrimination ability Poor Differential sensitivity Weak Discrimination ability Good Differential sensitivity High
- 3. Objectives • Just-Noticeable Difference (JND) “The minimum change of a physical stimulus that is necessary in order for a person to perceive the change 50% of the time.” (Lawless, 2010) • Aim of study • Determine the JND thresholds for the basic taste qualities (including Umami) and a selection of congruent odorants. • Hypothesis • JND thresholds of smell will be lower than of taste
- 4. Methodology (1/3) Sensory testing • 10 subjects, 21-28yr., 6 women-4 men, students • Discrimination testing: Paired comparisons • “which sample is more intense?” • Psychophysical method of constant stimuli • Test stimulus compared to a standard • Study design • 5 intensity levels • Constant Stimulus (CS): level 3
- 5. Methodology (2/3) Taste • NaCl • MSG • sucrose • caffeine • citric acid Olfaction • ‘smoked salt’ • ‘mushroom’ • ‘caramel’ • ‘coffee’ • ‘lime’ sniff / take a sip & expectorate "which sample is more intense?" Report response
- 6. Methodology (3/3) Data analysis Responses ‘stronger than the CS’ on the basis of 80 responses for each quality Psychometric functions Logarithmic transformation Transform into normal deviates (z-scores)) Estimate concentrations corresponding to z values of -0.675 and +0.675 (25% and 75% stronger than CS) (𝐂𝐨𝐧𝐜𝟕𝟓−𝐂𝐨𝐧𝐜𝟐𝟓) 𝟐 JND
- 8. Results (2/2) Tastant JND (g/lt) Odorant JND (g/lt) Salty 1.127 Smoked Salt 1.989 Umami 1.174 Mushroom 1.749 Sour 1.570 Caramel 2.718 Sweet 1.113 Coffee 2.424 Bitter 1.145 Persian Lime 2.189 Table 1. Overview of Just-Noticeable Difference thresholds of all qualities.
- 9. Conclusions Hypothesis Just-Noticeable Difference thresholds of smell will be lower than of taste • Higher JND thresholds for smell than taste • Taste: Good discrimination ability – Low JND Smell (compared to taste): Poor discrimination ability – High JND • Introduction of JNDs of Umami and odorants • Recommendations: More studies on determining JND thresholds for a wider range of odorants
- 10. Thank you for your attention! Questions??
- 11. Extra slide on Weber fractions • table • comparability
- 12. Weber fractions Taste Smell NaCl .102 Smoked Salt 1.989 MSG .107 Mushroom 2.629 Citric acid 2.070 Caramel 2.718 Sugar .037 Coffee 2.424 Caffeine .916 Persian Lime 2.189 (Schutz & Pilgrim, 1957)
Editor's Notes
- A typical indicator of differential sensitivity is the J-N-D threshold. It is defined as… As we noted in the previous slide taste has a high differential sensitivity, whereas smell has a rather poor sensitivity. In this study, we aimed at exploring this contrast, by determining…. Based on literature, we hypothesized that…
- For the study, we first recruited 10 subjects, 21-28 yo, … We then conducted a discrimination sensory test with paired comparisons, where the task of the participant was to judge which…. The most appropriate method to determine JND thresholds, is the method of CS, where the test stimulus … During the study, 5 distinct levels of intensity were tested, with the standard, constant stimulus being always level 3.
- For taste… participants evaluated solutions of Sodium chloride, MSG (monosodium glutamate) For olfaction we used… At the bottom of the slide the experimental protocol is depicted. We first presented each subject with the 5 pairs of samples, within each pair we had a test stimulus plus the standard, and we asked the subjects to either …. Depending on the sense that we tested that moment. They then had to judge …and finally report their responses on the score sheet that was provided.
- After carrying out the experiments, we first counted the ‘stronger than the standard’ responses… Based on the responses, we then obtained the psychometric functions for each quality. The data were first logarithmically transformed and then transformed into normal deviates. Later on, the Least-square regression of z scores was used to... The last step before calculating the JND, was taking half of the difference between these two concentration values following their back-transformation.
- “the increase of the physical stimulus (∆I) that is required to be just discriminably different from the starting level I.”