Biases and Path Dependency in the Even Swaps Method. Raimo P. Hämäläinen Tuomas J. Lahtinen firstname.lastname@example.org , email@example.com Systems Analysis Laboratory Aalto University, Finland sal.aalto.fi. Path dependency needs attention.
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Raimo P. Hämäläinen
Tuomas J. Lahtinen
Systems Analysis Laboratory
Aalto University, Finland
Biases affect the path and the path affects which biases are likely to take place
Smart Choices (1999)
Even Swaps is part of the PrOACT approach
Even swap: Alternative swapped to preferentially equivalent one that differs in two attributes
There is another alternative, which is equal or better than this in every attribute, and better at least in one attribute
Each alternative has the same value on this attribute
Commute time removed as irrelevant
(Slightly better in Monthly Cost, but equal or worse in all other attributes)Office selection problem (Hammond, Keeney, Raiffa 1999)
An even swap
Paths consist of different sequences of trade-off judgments
DM can experience the paths differently
Each path should lead to the same choice - does this happen?
Loss aversion (Tversky and Kaheman 1991)
Context dependent preferences (Tversky and Simonson 1992)
Tempting to always use money as the measuring stick
Scale compatibility (Tversky et al. 1988)
Modified alternative becomes more attractive than the preceding one
Contradicts preferential equality assumption of even swaps
Loss aversion gives extra weight for losses
Even swap: a reference change in one attribute is compensated by a change in another attribute
Attribute used as the measuring stick gets extra weight in trade-offs (Slovic 1990, Delquie 1993)
10€ (10€ equals 30 min)
20 min (10€ equals 20 min)
The weight of commuting time is higher when it is used as the measuring stick
This affects even swaps
Summer job selection task
Apartment selection task
Pricing path: Money used as the measuring stick
Hours path: Working hours used as the measuring stick
Smart-Swaps path (2 versions): Path suggested by the software
Fixed reference path: All swaps carried out in a single alternative
Same subjects in
all four comparisons
Same subjects in
Path dependency exists
More subjects select a high salary job on the pricing path (one-way p: 0.002)
More subjects select a low rent apartment on the pricing path (one-way p: 0.09)
People can feel that they should benefit from the trade-off
”I am willing to trade-off” vs.
”I am indifferent between the two alternatives”
Experiment with 82 subjects, reference group given typical instructions
Think of trade-off judgment from two reference points or
Think of trade-off judgment with two measuring sticks
Too much weight for the attribute that was first used as the measuring stick
Focus on the process especially important
Good practise in preference modeling (Payne et al. 1999, Anderson and Clemen 2013)
Select measuring stick attribute in which alternatives are initially close to each other
Carry out the same number of swaps in all the alternatives
Our Even Swaps experiment:
Scale compatibility and loss aversion bias coefficients
Credibility and transparency issues
Do paths have an impact?
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