Preference Reversals Induced by Screening:
The Biasing Effects of a Two-Stage Decision Process
Amitav Chakravarti, New York UniversityChris Janiszewski, University of FloridaGülden Ülkümen, New York University
2
Screening Is Beneficial
• There is ample evidence for two-stage decision process (e.g., Beach and Mitchell 1987; Bettman and Park 1980; Payne 1976)
• There is general agreement that prechoice screening is beneficial (e.g., Alba et al. 1997; Haubl and Trifts 1999; Lynch and Ariely 2000; Roberts and Nedungadi 1995)
– Reduces information overload
– Facilitates choice of the optimal alternative
• It is assumed that prechoice screening does not have any detrimental consequences. Why?
3
Two-Stage Process is Used in Complex Information Environments
BRANDS
A B C D E F
Attribute 1 Low Low High High High High
Attribute 2 High Low High High High Low
Attribute 3 Low Low Low Medium High High
Attribute 4 High Low Medium Low High Medium
Attribute 5 Medium High High High Medium Low
Attribute 6 Medium Low High High High Medium
4
Phased Decision Making: Stage 1a
BRANDS
A B C D E F
Attribute 1 Low Low High High High High
Attribute 2
Attribute 3
Attribute 4
Attribute 5
Attribute 6
5
Phased Decision Making: Stage 1b
BRANDS
A B C D E F
Attribute 1 Low Low High High High High
Attribute 2 High High High Low
Attribute 3
Attribute 4
Attribute 5
Attribute 6
6
Phased Decision Making: Stage 2
BRANDS
A B C D E F
Attribute 1 Low Low High High High High
Attribute 2 High High High Low
Attribute 3 Low Medium High
Attribute 4 Medium Low High
Attribute 5 High High Medium
Attribute 6 High High High
7
Can Screening Be Detrimental?
• Yes, if Stage 1 (prescreening) information is differentiating
• AND if people choose to deemphasize the prescreening information
• AND prescreening and postscreening information are not positively correlated.
A B C D E F
Attribute 1 Low Low Excellent High Excellent High
Attribute 2 Excellent High High Low
Attribute 3 Low Medium High
Attribute 4 Medium Low High
A B C D E F
Attribute 1 Low Low Excellent High Excellent High
Attribute 2 Excellent High High Low
8
Why Might People Deemphasize Prescreening Information?
• Explanation 1: People may not shift to a compensatory strategy in Stage 2. – Reconsidering prescreening information requires effort (Wright and
Barbour 1977).
• Explanation 2: People may shift to a compensatory strategy in Stage 2, but may ignore or deemphasize prescreening information. – The prescreening information has been “used” already (van Zee,
Paluchowski, and Beach 1992).
• Explanation 3: People may shift to a compensatory strategy in Stage 2, but the act of screening may alter perceptions of prescreening information. – The literature on perceptual categorization suggests the act of
categorization makes categorized items appear more similar (Goldstone, Lippa, and Shiffrin 2001).
9
Study 1
• 120 participants chose between six microwave popcorn brands (A, B, C, D, E, F)
• Each brand described by six attributes
– Four prescreening attributes
– Two postscreening attributes
10
Study 1: Stimulus Set Properties
Attribute Brand A Brand C Brand E Brand B Brand D Brand F
#1 Common Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
#2 Common Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Rank
#3 Alignable
SampleCrunchiness lasts 3.5 hours
Crunchiness lasts 3 hours
Crunchiness lasts 2.5 hours
Crunchiness lasts 2 hours
Crunchiness lasts 1.5 hours
Crunchiness lasts 1 hour
Rank
#4 Alignable
SampleCalories equal to less than a slice of bread
Calories equal to a slice of bread
Calories equal to two slices of bread
Calories equal to a pinch of sugar
Calories equal to a spoon of sugar
Calories equal to two spoons of sugar
Rank
#5 Nonalingable
Sample
Not tough Very crispy and easy to swallow
Few kernels left unpopped
Tastes a bit sweet
Slightly low in corn and grain flavor
Has some citric acid
Rank
#6 Nonalingable
Sample
With waterproof wrapping
Not likely to burn
Does not stick in teeth
Comes in a colorful wrapping
Requires a microwave bowl
Medium size kernels
PrescreeningAttributes
PostscreeningAttributes
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Study 1: Stimulus Set Properties
Attribute Brand A Brand C Brand E Brand B Brand D Brand F
#1 Common Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
#2 Common Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Rank
#3 Alignable
Sample
1
Crunchiness lasts 3.5 hours
Crunchiness lasts 3 hours
Crunchiness lasts 2.5 hours
Crunchiness lasts 2 hours
Crunchiness lasts 1.5 hours
Crunchiness lasts 1 hour
Rank
#4 Alignable
Sample
2
Calories equal to less than a slice of bread
Calories equal to a slice of bread
Calories equal to two slices of bread
Calories equal to a pinch of sugar
Calories equal to a spoon of sugar
Calories equal to two spoons of sugar
Rank
#5 Nonalingable
Sample
7 5 3 9 11 13Not tough Very crispy
and easy to swallow
Few kernels left unpopped
Tastes a bit sweet
Slightly low in corn and grain flavor
Has some citric acid
Rank
#6 Nonalingable
Sample
8 6 4 10 12 14With waterproof wrapping
Not likely to burn
Does not stick in teeth
Comes in a colorful wrapping
Requires a microwave bowl
Medium size kernels
PrescreeningAttributes-Most Influential-A > C > E
PostscreeningAttributes-Less Influential-A < C < E
>
>
>
>
<
< <
<
> > >
> > >
12
Study 1 Design
• Three between-subject groups.
– Control Group 1: Free Choice Group
– Control Group 2: Partitioned Choice Group
– Treatment Group: Screening Group
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Final Choice StageScreening Stage
Study 1: Procedures
Choose one brand
All information(6 brands, 6 attributes)
Rank Attributes
Free Choice Group
Rank Attributes
Shortlist 3 brands
Screening information(6 brands, 4 attributes)
Choose one brand
All information(6 brands, 6 attributes)
Screening Group
Rank Attributes
Partitioned Choice Group
Review information
Screening information(6 brands, 4 attributes)
Choose one brand
All information(6 brands, 6 attributes)
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Study 1: Choice Shares
59% 61%
35%
27%
38%
27%23%
5%10%
0%
25%
50%
75%
Free Choice Partitioned Choice Screening
A C E A C E A C E
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Screening Effect
• Participants who did not screen preferred the brand that performed best on the most important attributes (Brand A).
• Screening shifted market share to the brand that performed best on postscreening attributes (Brand E)
• What is the source of the screening effect?
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Study 2: Source of Screening Effect
• Explanation 1: People may not shift to a compensatory strategy in Stage 2. – Reconsidering prescreening information requires effort (Wright and
Barbour 1977).
• Explanation 2: People may shift to a compensatory strategy in Stage 2, but may ignore or deemphasize prescreening information. – The prescreening information has been “used” already (van Zee,
Paluchowski, and Beach 1992).
• Explanation 3: People may shift to a compensatory strategy in Stage 2, but the act of screening may alter perceptions of prescreening information. – The literature on perceptual categorization suggests categorization
makes categorized items appear more similar (Goldstone, Lippa, and Shiffrin 2001).
23
Study 2: Key Manipulation
Vary the hedonic dispersion of the postscreening information.
• Explanation 1 (continued noncompensatory processing):
– No influence of increases hedonic dispersion.
– If the screening effect is a consequence of the continued use of a noncompensatory process at Stage 2, then increasing the advantage of E > A should not matter.
• Explanation 2 (deemphasize prescreening information):
– Screening advantage increases with increased dispersion.
– Postscreeing information receives more weight.
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Study 2: Low Hedonic DispersionAttribute Brand A Brand C Brand E Brand B Brand D Brand F
#1 Common Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
#2 Common Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Rank
#3 Alignable
Sample
1
Crunchiness lasts 3.5 hours
Crunchiness lasts 3 hours
Crunchiness lasts 2.5 hours
Crunchiness lasts 2 hours
Crunchiness lasts 1.5 hours
Crunchiness lasts 1 hour
Rank
#4 Alignable
Sample
2
Calories equal to less than a slice of bread
Calories equal to a slice of bread
Calories equal to two slices of bread
Calories equal to a pinch of sugar
Calories equal to a spoon of sugar
Calories equal to two spoons of sugar
Rank
#5 Nonalingable
Sample
7 5 3 9 11 13Not tough Very crispy
and easy to swallow
Few kernels left unpopped
Tastes a bit sweet
Slightly low in corn and grain flavor
Has some citric acid
Rank
#6 Nonalingable
Sample
8 6 4 10 12 14With waterproof wrapping
Not likely to burn
Does not stick in teeth
Comes in a colorful wrapping
Requires a microwave bowl
Medium size kernels
25
Study 2: High Hedonic DispersionAttribute Brand A Brand C Brand E Brand B Brand D Brand F
#1 Common Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
Low cost per serving
#2 Common Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Low level of sodium
Rank
#3 Alignable
Sample
1
Crunchiness lasts 3.5 hours
Crunchiness lasts 3 hours
Crunchiness lasts 2.5 hours
Crunchiness lasts 2 hours
Crunchiness lasts 1.5 hours
Crunchiness lasts 1 hour
Rank
#4 Alignable
Sample
2
Calories equal to less than a slice of bread
Calories equal to a slice of bread
Calories equal to two slices of bread
Calories equal to a pinch of sugar
Calories equal to a spoon of sugar
Calories equal to two spoons of sugar
Rank
#5 Nonalingable
Sample
11 7 3 5 9 13Not tough Very crispy
and easy to swallow
Few kernels left unpopped
Tastes a bit sweet
Slightly low in corn and grain flavor
Has some citric acid
Rank
#6 Nonalingable
Sample
12 8 4 6 10 14With waterproof wrapping
Not likely to burn
Does not stick in teeth
Comes in a colorful wrapping
Requires a microwave bowl
Medium size kernels
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Study 2: Aggregate Choice Shares
58%53%
29%
22%
45%
22%21%18%
14%
0%
25%
50%
75%
Free Choice Partitioned Choice Screening
A C E
A C EA C E A C E
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Study 2: Choice Shares
58%
37%
25%
19%
35%
13%
0%
25%
50%
75%
Free Choice &Partitioned Choice
Screening
51%
19% 19%
24%
58%
20%
Free Choice &Partitioned Choice
Screening
Low Hedonic Dispersion High Hedonic Dispersion
[58.3-13.1]-[36.8-35] = 43.4% [51.4-20]-[19.4-58.2] = 70.2%
A C EA C E A C E A C E
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Study 2: Results
• The size of the screening effect increases with increased variation in postscreening attribute desirability
• People are indeed placing more emphasis on the postscreening information.
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Why Might People Deemphasize Prescreening Information?
• Explanation 1: People may not shift to a compensatory strategy in Stage 2. – Reconsidering prescreening information requires effort (Wright and
Barbour 1977).
• Explanation 2: People may shift to a compensatory strategy in Stage 2, but may ignore or deemphasize prescreening information. – The prescreening information has been “used” already (van Zee,
Paluchowski, and Beack 1992).
• Explanation 3: People may shift to a compensatory strategy in Stage 2, but the act of screening may alter perceptions of prescreening information. – The literature on perceptual categorization suggests categorization
makes categorized items appear more similar (Goldstone, Lippa, and Shiffrin 2001).
30
Two Goals of Study 3
• Further Investigate Explanation 2: Why do people ignore or deemphasize prescreening information.
– Reason 1: The prescreening information has been considered at Stage 1.
– Reason 2: The prescreening information has been used to select a set of options at Stage 1.
• Study 3 adds a passive screening condition: People rate alternatives and then an agent (computer) screens alternatives using these ratings.
– If Reason 1 (consideration) is correct, passive screening should result in a screening effect.
– If Reason 2 (using to select) is correct, passive screening should NOT result in a screening effect. People are not using the prescreening information to actively select a consideration set.
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Two Goals of Study 3
• Further Investigate Explanation 3: The act of screening may alter perceptions of prescreening information.
– Reason 3: Categorizing items makes within-category items appear to be more similar.
• Study 3 adds a condition that allows us to assess the influence of screening on the perception of prescreening information: People are asked to screen and rate alternatives. – If Reason 3 (increased homogeneity of prescreening information) is
correct, the ratings of retained alternatives should be more homogeneous after screening than before screening.
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Final Choice StageFirst Stage
Study 3: Procedures
Rate all brandsScreening information(6 brands, 4 attributes)
Rating Group
Choose one of three highest rated brands
See all information(6 brands, 6 attributes)
Shortlist 3 brandsScreening information(6 brands, 4 attributes)
Screening & Rating
Group
Choose one brandSee all information
(6 brands, 6 attributes)
Rate all brandsScreening information(6 brands, 4 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Choice Group
Partitioned Choice Group
Review information Screening information(6 brands, 4 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Shortlist 3 brandsScreening information(6 brands, 4 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Screening Group
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Study 3: Choice Shares
63%61%
41%
68%
56%
31%
17%
24%19%19%20%
73%
20%
14%13%
0%
25%
50%
75%
Free Choice PartitionedChoice
Screening Rating Screening &Rating
A C EA C E A C E A C E A C E
34
Study 3: Choice Shares
63%61%
41%
68%
56%
31%
17%
24%19%19%20%
7%
19%
14%13%
0%
25%
50%
75%
Free Choice PartitionedChoice
Screening Rating Screening &Rating
A C EA C E A C E A C E A C E
35
First Conclusion of Study 3
• Why do people ignore or deemphasize prescreening information?
– Reason 1: The prescreening information has been considered at Stage 1.
– Reason 2: The prescreening information has been used to select a set of options at Stage 1.
36
Study 3: Ratings Homogeneity
• Computed the mean variance of the ratings of the consideration set brands in the
– Rating Group = 3.04
– Screening and Rating Group = 1.61
– Significantly different (F(1, 80) = 7.32, p < .05)
37
Second Conclusion of Study 3
• Further Investigate Explanation 3: The act of screening may alter perceptions of prescreening information.
– Reason 3: Categorizing items makes within-category items appear to be more similar.
38
Study 3: Choice Shares
63%61%
41%
68%
56%
31%
17%
24%19%19%20%
7%
20%
14%13%
0%
25%
50%
75%
Free Choice PartitionedChoice
Screening Rating Screening &Rating
A C EA C E A C E A C E A C E
39
Third Conclusion of Study 3
• Why do people ignore or deemphasize prescreening information?
– Reason 1: The prescreening information has been considered at Stage 1.
– Reason 2: The prescreening information has been used to select a set of options at Stage 1.
– Solution: People can be encouraged to reconsider used information if it is made salient again, as we did with our rating task (screening and rating condition).
– Implication: Screening influences the perceived homogeneity, and the relative weight, of the prescreening information.
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Goal of Study 4
• Study 3 shows that active screening alters the perception and use of prescreening information. Why?
– Reason 1: “Active screening” occurs because decision makers use a noncompensatory process in Stage 1. Using the noncompensatory process at Stage 1 encourages a person to both discount prescreening information and see it as more homogeneous.
– Reason 2: “Active screening” occurs because of decision makers categorize (i.e., put alternatives into a consideration set) at Stage 1. Categorizing items makes within-category items appear to be more similar, hence less useful for making a choice.
• Study 4 adds a screen-by-rejection group
– In contrast to the screening group, the screen-by-rejection group excludes alternatives from the choice set.
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Goal of Study 4
• Study 3 shows that active screening alters the perception and use of prescreening information. Why?
– Reason 1: “Active screening” occurs because decision makers use a noncompensatory process in Stage 1. Using the noncompensatory process at Stage 1 encourages a person to both discount prescreening information and see it as more homogeneous. YES
– Reason 2: “Active screening” occurs because of decision makers categorize (i.e., put alternatives into a consideration set) at Stage 1. Categorizing items makes within-category items appear to be more similar, hence less useful for making a choice. NO
• Study 4 adds a screen-by-rejection group. Screening Effect?
– In contrast to the screening group, the screen-by-rejection group excludes alternatives from the choice set.
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Final Choice StageFirst Stage
Study 4: Procedures
Reject 3 brandsScreening information(6 brands, 4 attributes)
Screen-by-Rejection
Group
Choose one brandSee all information
(6 brands, 6 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Choice Group
Partitioned Choice Group
Review information Screening information(6 brands, 4 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Shortlist 3 brandsScreening information(6 brands, 4 attributes)
Choose one brandSee all information
(6 brands, 6 attributes)
Screening Group
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Study 4: Procedure
• Screening Instruction.
– After you have gone through these descriptions to your satisfaction, as a first step towards picking a brand of your choice, please shortlist three brands that you would consider more seriously for purchase. We will provide you with more information on these three brands on the next screen. Please do not make up your mind about your final choice yet; simply select (i.e., shortlist) three brands that you think warrant further attention by clicking on the appropriate buttons below.”
• Screen-by-rejection Instruction
– “After you have gone through these descriptions to your satisfaction, as a first step towards picking a brand of your choice, please reject three brands that you would not consider more seriously for purchase. We will provide you with more information on the three surviving brands on the next screen. Please do not make up your mind about your final choice yet; simply reject (i.e., throw away) three brands that you think do not warrant further attention by clicking on the appropriate buttons below.”.
44
Study 4: Choice Shares
60%56%
39%
55%
30%
23%21%22%
37%
16%13%
3%
0%
25%
50%
75%
Free Choice PartitionedChoice
Screening Screen-by-Rejection
A C EA C E A C E A C E A C E
45
Conclusion of Study 4
• Why does active screening alter the perception and use of prescreening information.
– Reason 1: “Active screening” occurs because decision makers use a noncompensatory process in Stage 1. Using the noncompensatory process at Stage 1 encourages a person to both discount prescreening information and see it as more homogeneous.
– Reason 2: “Active screening” occurs because of decision makers categorize (i.e., put alternatives into a consideration set) at Stage 1. Categorizing items makes within-category items appear to be more similar, hence less useful for making a choice.
46
Summary of Studies
Naïve Expectation Result
Study 1 & 2Does screening effect occcur when Stage two processing is noncompensatory? It Must N/A
compensatory? No Yes
Study 3Does the screening effect depend changes in the ___ of prescreening information at Stage two choice? weight Yes Yes
value No Yes
Study 3Does the screening effect depend on ___ prescreening information in Stage one ? considering Yes No
classifying via No Yes
Study 4 Does the screening effect depend on the Stage one process (noncompenatory)? Yes No
outcome (CS formation)? No Yes
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Conclusions
• Screening can alter decision making when prescreening and postscreening information is negatively correlated.
• Screening appears to influence the perceived homogeneity of prescreening information and the relative importance of this information (as compared to postscreening information).
• Inclusionary, as opposed to exclusionary, screening is responsible for the screening effect.
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General Discussion
• Implications of creating a consideration set via screening (and increasing the perceived homogeneity of prescreening attributes)– Increased price sensitivity if price is not a screening attribute (e.g.,
Diehl et al. 2003).
– Delay decision to purchase (e.g., Dhar 1997).
– Desire to search for additional, less important information (e.g., Moorthy, Ratchford, and Talukdar).
• Issues– Why does classification reduce differentiation on the classification
variables?
– When do people engage in inclusionary, as opposed to exclusionary, screening?