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65 Cards in this Set
- Front
- Back
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What is psychophysics?
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The oldest branch of experimental psychology that studies the relationship between stimuli and sensory experience.
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What is Weber's Law?
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ΔI/I = k; The amount a physical stimulus needs to be increased to be just percievably different is a constant ratio, where ΔI is the increase in the physical stimulus needed to be different and I is the starting level of the stimulus
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What is Fechner's Law?
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S = k log I
The concept that the magnitude of a subjective sensation increases proportional to the log of the stimulus intensity, where S is sensation intensity and I is physical stimulus intensity. |
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Describe the Method of Limits
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A physical stimulus is changed by successive discrete steps until a change in response is noted. If the stimulus is increasing, the response will change from 'no sensation' to 'I detect something'. If the stimulus is decreasing, the response will change back to 'no sensation'. Over many trials the average point of change can be taken as the person's absolute threshold, which is the minimum intensity required for detection of the stimulus.
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Describe the Method of Constant Stimuli
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A stimulus is always compared against a constant reference level, usually the middle point on a series of physical intensity levels. On presentation of a stimulus, a subject responses with 'greater than' or 'less than' the standard. Many replications of each intensity level are presented and a frequency count of the number of times a level is judged stronger than the standard is determined.
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Describe the Method of Adjustment
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A subject is given control over a variable stimulus and is asked to match a standard. The method can be used to determine difference thresholds based on the variability of the subject over many attempts at matching.
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Describe the Method of Single Stimuli
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A direct application of rating scales to the intensity of sensations; one stimulus presentation yields one data point.
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Describe the Psychophysical Power Law
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Perceived sensation is a power function of stimulus intensity. Different stimuli have characteristic exponents. The function forms a straight line in a log-log plot with the exponent indicated by the slope of the function.
S = n log I + log k, where n = the characteristic exponent k = a proportionality constant determined by the units of measurement |
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actoryhe meaning of a power function that has an exponent less than 1 (as is the case with most olfactory sensations)?
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This means that larger and larger physical increases are needed just to maintain a common proportional increase in the sensation level. These functions are negatively accelerated.
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What is the meaning of a power function that has an exponent greater than (as is the case with most trigeminal sensations)?
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This means that as physical stimulus increases, responses increase at a much more rapid rate (ex. sweetness intensity of sugar).
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What is cross modality matching?
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Separate scaling functions are derived for two continua; one continua is then scaled as a function of the other without using numbers (ex. subject is told to adjust sensation proportions of two lights to match sensation proportions of two tones).
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What are the advantages of equation:
R = (Rmax C)/(k + C) for describing the relationship of stimulus and sensation compared with the Stevens and Fechner equations? |
This equation is based on physiological principles; for example, kinetics of enzyme-substrate relationships. When plotted, the function forms an S shaped curve with an initial flat portion, steep rise, and then another flat zone representing saturation of response at high levels. This makes sense - response levels at below threshold should hover around a baseline and then grow faster, and should approach a max when all receptor sites are filled. Neither Fechnerian nor Stevens power functions do this-- both continue upwards indefinitely which is unrealistic.
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Where in the mouth can you find taste buds?
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-Interspersed among the filiform papillae, especially on the front and edges of the tongue
-In foliate papillae along the sides of the tongue -In circumvallate papillae on the back of the tongue -The soft palate just behind where the hard part of the palate stops -Root of the tongue and upper part of the throat |
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Why is the map of the tongue showing different areas of the tongue responsible for perceiving different tastes inaccurate?
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Any one of the four classical taste qualities can be perceived on any area of the tongue, so the map of the tongue with different tastes in different areas is not accurate.
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What is adaptation?
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A decrease in responsiveness under conditions in constant stimulation.
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How intense is a 0.1M NaCl solution after adapting to water compared to the intensity of a 0.1M NaCl solution after adapting to a 0.1M NaCl solution? (Fig 2.6, pg 45)
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The 0.1M NaCl solution is more intense after adapting to water than after adapting to a 0.1M NaCl solution. At the adapting concentration 0.1M NaCl, there is little or no taste.
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If you prepared a spaghetti sauce in a laboratory, then rated the intensity of its flavor in that same laboratory, how would you expect the rating of flavor intensity to differ from the sam erating made in a room free of the source of odor?
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The intensity would be lower when rating in the same room as preparation due to adaptation. The sauce would appear more intense in a room free of the sauce odor.
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Give an example of mixture suppression
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Mixture suppression: all four classical taste qualities show an inhibitory pattern when combined. For example, a solution of quinine and sucrose is less sweet than an equal concentration of sucrose tasted alone. Similarly, the mixture is less bitter than equimolar quinine tasted alone.
Another example: In fruit beverages, the sourness of acids can be partially masked by sweetness from sugar. The sugar serves a duel role adding its own pleasant taste while decreasing the intensity of what could be an objectionable level of sourness. |
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Give an example of synergism or hyperadditivity among tastes
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Hyperadditivity - implies there is a higher taste intensity in the mixture than would be predicted on the basis of simple addition of component effects.
Example: the interaction of MSG with ribosides which produces strong taste sensations Example: sweetness from salt in low concentrations added to sugar (NaCl has an intrinsic sweet taste that is normally masked by saltiness at higher levels, so the small increase in sweetness noted with addition of NaCl is due to this intrinsic sweet taste of dilute NaCl) |
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What is release from suppression? Give an example
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Mixtures of tastes suppress the intensity of the individual tastants. However, after adaptation to one of the tastes in a mixture and exposure to the mixture, the non-adapted tastant is perceived at the same intensity as an equimolar unmixed solution of the tastant.
Example: Sweetness of sugar and bitterness of quinine are partially suppressed when present in a mixture. After adaptation to sucrose, the bitterness of a quinine/sucrose mixture rebounds to the level it would be perceived at in an equimolar unmixed quinine solution. |
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What does it mean if you are a nontaster of PTC? If you were a PTC nontaster would you find a diet soda sweetened with saccharin (which tastes both sweet and bitter) more or less sweet than a taster? Why?
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A PTC nontaster can not detect the substance until it is several thousandfold higher than the concentration detected by most people. A PTC nontaster would find a diet soda sweeter than a supertaster; there is some evidence that nontasters do not show some mixture suppression effects. Since a nontaster does not perceive bitterness, there is no inhibition. Thus, the sweetness may be enhanced, in a similar fashion to the effect of release from suppression.
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What is cross adaptation?
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In a cross-adaptation paradigm, the receptors are adapted to one compound, and then a second test compound is presented. If the second compound has reduced taste intensity relative to its reponse following water adaptation, then some overlap in peripheral mechanisms of stimulation is expected.
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How can you tell what part of a flavor is taste and what part is smell? (Never mind trigeminal for this question)
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Pinch your nose shut. Pinching the nose shut effectively blocks the retronasal passage of flavor volatiles up to the olfactory receptors.
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Where is the olfactory epithelium?
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Very high in the nasal cavity (pg. 50) -- this serves a protective function, but also means that only a small percentage of airborne substances flowing through the nose actually reach the sensory organs
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About how long does an olfactory receptor cell last? How long does a taste cell last?
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Olfactory receptor cells last about 1 month, taste cells last about 1 week
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What is anosmia? Specific anosmia?
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Anosmia is a condition of total loss of smell. Specific anosmia occurs when an individual with an otherwise normal sense of smell is unable to detect some families of similar smelling compounds. Specific anosmia is operationally defined as a condition in which an individual has a smell threshold more than 2 standard deviations above the population mean concentration.
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Why do people have such a hard time discriminating differences in odor intensity?
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Due to difficulties in stimulus control and delivery; headspace (which is often sampled by a subject in an odor discrimination study) can vary in concentration quite a bit from the nominal concentration present in a liquid phase. This unwanted variation was highly correlated with discrimination performance in research studies, with stimulus variation accounting for 75% of the variance in discrimination.
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What are some examples of trigeminal or chemesthetic sensations?
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-Fizzy tingle from CO2 in soda
-Burn from hot peppers -Pungency from black pepper and spices such as ginger and cumin -Nasal pungency of mustard and horseradish -Bite from raw onions and garlic |
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What is the desensitization to capsaicin?
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Numbing of the oral tissues; occurs when stimulation is followed by a short rest period
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What is astringency? What causes it? What happens to perceived astringency when an astringent substance is repeatedly sipped?
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Astringency is a group of chemically induced oral tactile sensations ASTM: "the complex sensations due to shrinking, drawing, or puckering of the epithelium as a result of exposure to substances such as alums or tannins"
Lee and Lawless: "A complex sensation combining three distinct aspects: drying of the mouth, roughing of oral tissues, and pucker or drawing sensations. -It is caused by tannins and alums. -When an astringent substance is repeatedly sipped, perceived intensity of astringency increases. Astringent substances tend to cause a buildup of tactile effects rather than a decrement as one might see in taste adaptation. |
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If you add a smell to a taste (eg. if you had a sugar solution that tasted sweet and added some vanilla flavor that had no taste) would the smell and the taste suppress each other or would the two intensities simply add together? Why is this not a simple question?
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The two intensities would have an additive effect. Subjects often misattribute volatile sensations to 'taste'. Retronasal smell is poorly localized and often perceived as a taste from the oral cavity. Therefore, the nostrils need to be pinched shut to prohibit the retronasal passage of volatile materials. It has also been observed that harsh tastes generally suppress, and pleasant tastes generally enhance volatile flavor.
This is a hard question because it depends on the compounds. |
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Give an example of confusion between a hedonic and an intensity judgement (pg. 69)
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Von Sydow et al examined ratings for taste and odor attributes in fruit juices that varied in added sucrose. Ratings for pleasant odor attributes increased and those for unpleasant odor attributes decreased as sucrose concentration increased. In other words, the overall hedonic reaction causes a correlation among rates for attributes. Increases in unpleasant flavor notes will cause decreases in intensity ratings for pleasant characteristics.
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When trigeminal sensations and olfactory sensations are both present, do they suppress each other? Or are they perceived independently?
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They suppress each other-- the first work done found mutual inhibition of smell by carbon dioxide in the nose.
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Group tests into those that be used to determine any difference between two samples and those that can be used to determine a specific difference between two samples. Are there some tests that could fit into both classes? which?
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Tests that be used to determine any difference:
Triangle Duo-Trio A-Not-A Two-Out-of-Five ABX Tests that can be used to determine a specific difference: 2-Alternative Forced Choice n-Alternative Forced Choice Two-Out-of-Five Harris Kalmus Both: Two-Out-of-Five Harris Kalmus |
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Explain why the significance of a difference test is not a good measure of the size of the difference, but the proportion of the judges that respond correctly is a good measure of the size of the difference.
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Significance of a difference test is not a good measure of the size of the difference because the test does not indicate the magnitude of the sensory difference, only if a difference is likely to be perceived or not.
The proportion of judges that respond correctly is a good measure of the size of difference. For example, a comparison in which 95% of the judges answer correctly has a larger sensory difference between control and test samples than a comparison in which only 50% answered correctly. |
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Distinguish between Type I and Type II errors.
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Type I - Null hypothesis is rejected when it is actually true. It is controlled by the chosen level of significance of alpha. If alpha = 0.05, there is a 1 in 20 chance of making a type 1 error. (ex. in a discrimination test, two products are concluded to be perceivably different when they are not actually perceivably different).
Type II - Null hypothesis is accepted when it is actually false; controlled by the level of beta; the risk of not finding a difference when there actually is a difference. |
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Give an example of a sensory test objective where the Type I error is most important to minimize
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Type I error should be minimized when you want to be certain that two samples are perceivably different.
Example: Does the new peanut brittle formula result in brittle that is crunchier than the old formula? Alpha is set at 0.01, and 2-AFC test is performed. The data indiates the null hypothesis should be rejected. If this is true, this means the new formulation is crunchier than the old. If a type I error has been committed, the null hypothesis is actually true, and there is NOT a difference. |
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Give an example of a sensory test objective where the type II error is most important to minimize
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Type II error should be minimized when you want to be certain there is no perceivable difference between samples.
Example: Is the new vanilla ice cream formula detectably different from the old formula? Triangle test is performed and the data indicates that the null hypothesis should not be rejected. If this is true, this means that the two formulations are not perceviably different. If a Type II error has been committed, the null hpothesis is actually false, and there IS a difference. |
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How are measures of the proportions of hits and false alarms turned into d'? (be sure you can correctly convert hits and false alarms to the desired Z values) Figure 5.4
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d', the value of the sensory difference, is equal to the Z-score for the proportion of hits minus the Z score for the proportion of false alarms, where hits are presentation of a signal with a 'yes' response, and false alarms are presentation of noise with a 'yes' response.
(draw graph) |
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If subject A is more sensitive to the test aroma than subject B, how would you expect the ROC curves for the two subjects to differ?
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We would expect the curve for subject A to bow more towards the upper lefthand corner of the ROC curve; higher sensitivity is equivalent to a higher level of discrimination.
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Using Figure 5.8 and the discussion of the paradox of the discriminatory nondiscriminators - why might someone be able to identify B as 'sweeter' than A in a 3-AFC test, but not be able to correctly select B in a triangle test with 2 samples of A?
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One of the duplicate samples in a triangle test is perceived as being more similar to the odd sample (judgement is incorrect), but when asked to find the sample with the strongest sensation, the answer is correct (pg. 155)
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What are some other reasons a person would find the triangle test more difficult than the 3-AFC test?
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-With a 3-AFC test, judges are given a specific attribute to focus on which focuses the sensory test; with a triangle test, they are asked to identify the odd sample, unaware of which attribute is different.
-Triangle test entails a correct decision based on the comparison of 3 product differences and discerning for which pair these perceived differences are smallest. 3-AFC only requires correctly choosing the strongest or weakest item and not comparing relative differences. -Chance variation of other attributes in the sample may capture the attention of the panelist, raising the possibility of a momentarily large difference among the two duplicates. -Sequential adaptation effects of strong vs. weak samples in a triad can affect the probability of making the correct choice in discrimination tasks. |
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Describe the R-Index test. What does it measure?
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The R-Index was developed to provide and index of discrimination ability without the stringent assumptions entailed by d' (ie. equal and normally distributed variances from signal and noise distributions). The R-Index converts rating scale performance to an index related to the percentage of area under the ROC curve, giving an indication of what we would expected as performance in a 2-AFC test (A higher R-value indicates less overlapping response patterns, and better discrimination).
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You determine that fewer than 30% of your population can detect a difference in your products. Where and how would you get the information that 30% is important?
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-Professional judgement
-Knowledge of the products -Business situation regarding consumer expectations about product consistency (pg. 168) |
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Define theshold
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Absolute or detection threshold is the energy level below which no sensation would be produced by a stimulus and above which a sensation would reach consciousness (A range exists below which the odor or taste of a substance is not detectable and above which individuals with a normal sense of smell or taste would readily detect the substance; detection threshold is the lowest concentration at which a substance is perceivable)
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Give two examples of situations in which knowing the threshold for some compound would be useful
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1. In the determination of flavor chemicals that may contribute to the aromatic properties of a natural product
2. In defining a threshold for taints or off-flavors in a product (ie. acceptable vs. unacceptable levels of undesired flavor components) 3. In screening individuals for their sensitivity to key flavor components |
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What are some factors that affect the measurement of a threshold?
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-Threshold is a momentary state and is difficult to replicate
-Individual response biases; it is difficult to separate effects of response criteria from actual detection ability of the person -Measured value for threshold is defined different by different psychophysical methods (ie. not a fixed value that has meaning beyond the exact procedure used to determine it) -Individual variability in a group of people and within an individual over repeated measurements challenge the idea that threshold is a fixed value. -It is highly dependent upon purity of the stimulus, physiological state of the subjects, subjects level of practice with the method, and their degree of attentiveness and motivational state -The difficulty level of the test will affect performance |
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Distinguish between detection and recognition thresholds
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Detection - the lowest concentration that a substance is perceivable
Recognition - minimum levels of a stimulus that take on the characteristic taste or smell of the stimulus and are often a bit higher than detection thresholds (ex. At low concentrations just about its detection threshold, NaCl is perceived sweet; the concentration at which a salty taste is apparent (recognition threshold) is higher). |
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What is a terminal threshold?
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The region in which no further increase in response is noted from increasing physical stimulus intensity (ie. sensory response has reached some saturation level).
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Describe the Method of Limits for determining a threshold
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Stimulus intensity is raised in an ascending series and then lowered in a descending series to find points at which the observer's response changed from a negative to a positive response or from positive to negative.
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What are two problems with the Method of Limits for determining a threshold that are solved by using the ascending series of 3-AFC tests?
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1. Descending series may cause fatigue or sensory adaptation; observer fails to detect stimulus presentations that would be clearly perceived if presented in isolation
2. Error of habituation - subjects show a tendency to stick to the response they have just made; conversely, error of adaptation - a tendency to change responses prematurely since the participant knows that the stimuli are increasing or decreasing and that a change is expected. By forcing the judge to discriminate the target stimulus from background level at each step, the above problems are avoided |
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What was Amoore's operational definition of specific anosmia?
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A condition of having olfactory detection thresholds more than two standard deviations above the population mean.
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Why would you wan to have judges do a 2-out-of-5 test or 4-out-of-8 test at each concentration level in a threshold test instead of a 2-AFC test or a triangle test?
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Chance probability of obtaining correct sorting by merely guessing a 2 out of 5 test is 1 in 10; the chance probability of a triangle test is 1 out of 3 and of a 2-AFC test is 1 out of 2, which is much higher. In other words, chance performance is minimized.
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There was one study that measured thresholds of a few people repeatedly. How much variation did they see in the thresholds of individual people?
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Individual thresholds varied 2,000-10,000 fold in concentration of odorans (day-to-day variation is large and thresholds for an individual are sometimes unstable)>
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What tasting stragety can be used to minimize adaptation while decreasing the chance probability of a correct detection at any level during a threshold testing procedure?
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Use fewer presentations of the target stimulus (ex. A 4-AFC with one target and 3 blanks); this raises the chance performance level, but lessens potential adaptation at any one concentration step. To guard against the effects of correct guessing, threshold is taken as the lowest concentration step with a correct choice when all higher concentrations were also correct. Thresholds are measured in duplicate ascending runs in a test session and a duplicate session of two more ascending runs is performed on a second day.
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Why is the geometric mean a useful measure of central tendency when there are a few unusually high values in a data set?
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The geometric mean is less influenced by high outliers in data. Using a common mean (which is more influenced by high outliers) may result in skewed data.
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What is the 'problem' in using statistical significance for determining thresholds?
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The statistical significance of any results depends not only on the group percent correct, but also on the number of judges participating. Using statistical significance therefore leads to the nonsensical result that lower thresholds are estimated as the number of testers increases.
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Describe the method proposed by Lundahl et al 1986 for determining a threshold. What, according to the text authors, is a serious weakness of this method?
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The procedure involved the use of rated difference scales, where a sample containing the to-be-recognized stimulus is compared to a control or a blank stimulus. In this procedure, ratings for the sensory difference from the control sample will increas as the intensity of the target gets stronger. This procedure is based on the significance of t-statistics, which means that the value of threshold and the intervals will depend on the number of observations in the test; this leads to the nonsensical situation where the threshold value will decrease as a function of the number of observers in the test design, an irrelevant variable.
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What do the authors mean by "adaptive" procedures for determining thresholds?
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Adaptive procedures are those in which the next stimulus intensity level to be tested depends on detection or nondetection at the previous interval. If the subject is incorrect, the stimuli will increase in intensity, and if the subject is correct the stimuli will decrease in intensity; an average can then be taken.
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What is an ogive?
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The S-shaped function derived from the cumulative normal distribution.
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How can an ogive be transformed to a straight line?
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The points can be plotted on probability paper (a graph in which equal standard deviations are marked off along the ordinate, stretching the numeric intervals at the ends and compressing them in the midrange to conform to the density of the normal distribution), or the data can be transformed by taking z-scores.
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What is an odor unit?
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A calculate value based on the threshold dilution ratio and the concentration of the odorant where,
Z = C/Ct Z is the threshold dilution ratio measured by an olfactometer C is the odor concentration Ct is the theoretical minimum concentration of the odor for detection in 50% of the population. According to this calculation, only compounds with odor units greater than 1 will contribute to the aroma of the product. |
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What is a Scoville unit?
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Scoville units are dilution factors, commonly given as mL/g. The value refers to the number of dilutions necessary for sensations to disappear as an estimate of potency. Scoville units are used to measure the pungency of peppers as defined by the amount of capsaicin they contain.
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How are odor units and scoville units the same?
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Both use dilution to threshold as a measure of sensory impact.
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What is the statistical power of a test?
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1-beta, beta is type II error; it is the probability of finding a difference if one actually exists, or the probability of making the correct decision that two samples are perceptibly different. Power is dependent upon the magnitude of difference between the samples, the size of alpha, and the number of judges performing the test.
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