Sensory Test Ii - Chapter 9

Front 1

How can one develop a frame of reference for subjects doing a category scaling task?

Back 1

- Preliminary practice with the scale & exposure to the general range of stimuli and correlation to given response scale

- Stimulus end-anchors are v. important to help define the frame of reference; they should brackett the expected sensory range

Front 2

What are the two processes contributing to the ratings assigned to a stimulus by a person?

Back 2

1. Psychophysical transformation - stimulus energy is translated into physiological events that have as their result some subjective experience of sensory intensity

2. Response Output transformation: the function by which the subjective experience is translated into the observed response

2.

Front 3

Which one of the two processes would be affected by
1. Adaptation?
2. Anosmia
3. Mixture suppression
4. By using standards to illustrate scale extremes
5. By judges ability to use numbers for a ME task?

Back 3

1. 1
2. 1
3. 1
4. 2
5. 2

Front 4

Give a definition of a response bias

Back 4

A shift in response to a constant sensation due to a change in the contextual situation

Bias is a negative only ig there is a reason to presume that one condition of judgement is more accurate than all others

Front 5

What is a contrast effect?

Back 5

Stimuli are judged more intense in the presence of a weaker stimulus & vice-versa

Front 6

What is an assimilation or convergence effect?

Back 6

The opposite of contrast: for example, a good sample may be rated lower when following a poor sample

Front 7

Describe Helson's adaptation Level Theory

Back 7

Helson proposed that we take as a frame of reference the average level of stimulation that has preceded the item to be evaluated (ie 40°F seems warm after winter but cold after summer)

Front 8

What is the reversed pair technique?

Back 8

Two tests:

Target stimuli: odor w/citrusy & woody notes

Contextual-inducing sample 1st (say it’s wood); target 2nd (say it’s odor)
 the citrus odor is rated more intensely after wood
Is it due to context effect or is it due to adaptation/carryover?

Run the reverse pair:
 odor 1st and wood 2nd
Response pattern will tell you the answer. If the effect goes away, then it’s adaptation, but if it stays, supposedly it’s contextual.

Front 9

Give an example of a shift in sensory intensity rating due to a shift in the range of stimulus intensity.

Back 9

Target sample = 'A' (let's say a set concentration of salt)

When A is served with lower concentration solutions, A will likely receive a higher saltiness rating than when it is served with higher concentration solutions

Front 10

Give an example of a shift in sensory quality ratings due to a shift in the quality context.

Back 10

Example: Terpene
Terpene is judged as 'too citrusy' for includion with woody/pine like scents

Terpene is judged 'too woody' when presented with citrus scents

Front 11

Give an example of a shift in liking ratings due to a shift in stimulus context

Back 11

Contrast rather than convergence is the general rule.

A good product tends to be given higher liking scores when it is following poorer items

e.g. a model solution receives higher 'pleasantness' ratings when embedded in a series of quinine solutions compared to when it is embedded in a series of sucrose solutions

Front 12

How does the range frequency theory differ from the idea that the frame of reference is based on the average of the sensory experiences?

Back 12

This theory states that it is the distribution (frequency & range) of items within a psychophysical experiment that influence judgements

-- It is not only the average level that is important, but also how the stimuli are grouped and spaced along the sensory continuum

Front 13

What is the frequency principle? How does increasing the frequency of presentation of a sample affect the slop of a line relating stimulus concentration to sensory intensity?

Back 13

Frequency Principle - subjects tend to spread ratings of similar intensity items when they're present w/greater frequency

This results in a local steepening of the psychophysical response function.

Front 14

Give an example of a "real life" situation where you would expect to see a frequency effect (draw distribution and effective psychophysical response)

Back 14

Rating the presence of off-flavors or taints: if a lot of "free-from-taint" and weakly tained samples are served with only a few strongly tainted samples - high frequency at low concentrations = steepened curve & higher than expected ratings

Front 15

What is the range principle? How does increasing the range of stimulus intensities affect the slope of a line resulating stimulus concentration the sensory intensity?

Back 15

Range effects occur in category rating and in other judgements including ratio scaling.

Range principle: subjects will map their experiences into the available categories to fit the range of products

Smaller range = steeper phychophysical functions

Front 16

Contrast the effect of using an anchor stimuli that is about the same size as the strongest stimuli a particupant would experience during a test vs using anchor stimuli that is much more extreme that would would be encountered during the study

Back 16

I_anchor ~ I_Max: Subject distribute their scores across the range ina nicely graded fashion / strong effect of these anchor stimuli on the use of rating scales

I_anchor >> I_Max:
The influence of anchors tend to diminish as if they had become irrelevant to the judgemental frame of reference

Front 17

What is the contraction or assimilation bias? Where has assimilation been observed?

Back 17

These biases are the opposite of contrast. It includes a tendency to rate close to the scale center or a reference value. People tend to underestimate high/low values.

- is has been observed when a stimuli follows a very strong stimuli: it's overestimated ("Local contraction")

Front 18

What is the logarithmic response bias?

Back 18

This is observe with open ended scales like M.E. Ratings with increasing intensity change patterns - 2 - 10 ok, but when they get >10, you get log-jumps in data. (ie 20 is given since it's 2x 10 but really the person should have based rating off the orginal '2')

Front 19

What is the transfer bias?

Back 19

The tendency to use previous experimental situations & remembered judgments to calibrate oneself for later tasks. Very common when judges are reused.

Positive: judges are "calibrated"

Negative: judgments may not shift appropriately

Front 20

What are some physiological differences among people that could produce some idiosyncratic scale usage? Describe what difference in scale use you could expect from them.

Back 20

- Anosmia: all ratings would be low

- Non-taster: low bitterness ratings

- Desensitized to hot peppers (frequent consumers): low ratings

Front 21

What is a halo effect?

Back 21

When high ratings of one positive sensory attribute elevate ratings of other positive sensory attributes.

Front 22

In figure 9.10, how do you explain the higher ratings for sweetness, creaminess, and thickness produced by the added vanilla flavor?

Back 22

Two reasons:
(1) There is no scale for vanilla flavor
(2) halo effect

**Untrained consumers cannot be trusted to provide information that is an accurate sensory spec. of product characteristics (confusion within the senses)

Front 23

What is dumping? Give an example. Explain how the dumping in your example could have been minimized

Back 23

If an attribute is omitted from a questionnaire, consumers will find a way to dump their liking or distaste for that attribute into other scales. **Restricting responses may affect ratings**

Front 24

What is the opposite of dumping? How can you minimize it?

Back 24

Providing too many response scales may cause over-partitioning of sensations into inappropriate response categories, decreasing intensity reported.

Minimize this (& dumping) through careful pretesting/discussion in descriptive training.

Front 25

Describe these psychological errors:
- Error of anticipation

Back 25

"Jumping the gun" - observer is expecting a sensation & prematurely reports it

Front 26

Describe these psychological errors:
- Error of habituation (how do you minimize this & previous?)

Back 26

Judge perseveres on the previous response; may result from lack of attention or motivation of panelist or personal vs strict criteria.

To avoid this and the previous error you randomize sample presentation

Front 27

Describe these psychological errors:
- Stimulus error
& how to avoid?

Back 27

When observer knows/presumes to know identity of stimulus & draws inference about what it should be based on expectations. To minimize this error you put in "surprise" samples

Front 28

Describe these psychological errors:
- Time order error (positional bias)

Back 28

An effect of sequence. One order of evaluating 2 or more products produces different judgments than another order.

This is why serving order is balanced.

Front 29

One possible solution to these biases is to serve only 1 sample at a time in a test. What are the disadvantages to this?

Back 29

Impractical: Highly inefficient to have trained panelists rate only 1 thing each trip

- Monadic tests do not take advantage of human's innate ability to compare

-Transfer bias still exists

Front 30

What are some disadvantages to comparing ratings from separate sessions or separate experiments?

Back 30

Contextual effects would be different;

ratings are not absolute & judges use scale differently - would need a control in the mix

It would not be possible to say whether difference that arose between the products did so because of true differences or from differences cause by contextual effects on the responsess

Front 31

Describe some strategies for stabilizing ratings across experimental sessions

Back 31

Control for and minimize contextual biases

(1) Randomize & counterbalance
(2) stabilize - keep context the same across sessions
(3) Calibration - training
(4) Interpretation - carefully consider if contextual biases may exist

Front 32

How does one calibrate judges?

Back 32

By providing a number of intensity reference standards across the range tested

This establishes a stable frame of reference

Front 33

If you add an ingredient "to taste" at the bench top, what biases might influence your ingredient level?

Back 33

Affective shift - low concentrations and up; you are likely to find a low "just right" level

Adaptation to that ingredient