Connecting commitment to self-control: Evidence from a field

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Connecting commitment to self-control: Evidence from a field
Connecting commitment to self-control: Evidence
from a field experiment with participants in a
weight loss challenge
Séverine Toussaert (NYU)
August 27, 2014
Introduction (1): Theoretical Literature
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Rapid expansion of the self-control literature over the last 15
years, both theoretical and empirical
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At a theoretical level, 2 approaches:
1. Behavioral economics approach (Laibson 1997):
) Temptation identified with choice reversals (time
inconsistency)
) Only one remedy: commitment
2. Decision theoretic approach (Gul and Pesendorfer 2001):
) Temptation identified through a preference for restricted
choice sets.
) Two remedies: commitment ex ante and exercise of
self-control ex post.
Introduction (2): Theoretical literature
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Differences with behavioral econ approach:
1. interest for foundational question: how to identify temptation?
2. Identification through choice experiments, revealed preference
3. dynamically consistent preferences
4. can rationalize the exercise of self-control:
{salad }
1
{salad , hamburger } and salad
2
hamburger
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In particular, commitment can be justified even in the absence
of choice reversals ) eliminates the cost of self-control.
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Consequence: welfare may be improved by removing unchosen
alternatives. Example: removing chocolates at cashier.
Introduction (3): Empirical Evidence
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At an empirical level:
1. Many field and lab experiments; mostly inspired from the
dynamic inconsistency literature. In a typical experiment:
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Participants are offered a given commitment device
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Study of correlation between take-up and preference reversals
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Take-up often low; not clear what factors explain take-up
2. No experiment testing decision theory models of temptation
(while decision theory swears by choice experiments!).
3. In particular, almost no attention devoted to studying:
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the link between the choice set faced by the DM and his desire
for commitment.
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the trade-off between commitment and flexibility
Introduction (4): Goals of this study
1. Provide new evidence on the existence of a demand for
commitment devices with a selected sample of people who:
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face self-control problems in managing their weight
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are aware of their problems
2. Construct a new dataset of choices between menus, which
allows to:
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test existing decision theory models of temptation and
self-control (Gul and Pesendorfer 2001)
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study the trade-off between commitment and flexibility
3. Study correlations in the demand for commitment across
different domains:
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Are there “Commitment types”?
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What common determinants may explain decisions to restrict
choice behavior?
Introduction (5): What this study does
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Gathers field data on participants in a weight loss challenge
organized by NYU.
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Participants offered two commitment devices:
1. Receive their payment for the study only if they achieve
self-set attendance goals
) activities with immediate costs and delayed benefits
2. Limit the coverage of a lunch reimbursement program to
only certain food categories
) indulgent eating has immediate benefits and delayed costs
Introduction (6): Questions this study asks
1. Are participants willing to constrain their choices by
setting goals or limiting what they are incentivized to eat?
2. What type of restrictions to the reimbursement program
tend to be preferred?
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How much flexibility do people seek to retain?
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How well can existing decision theory models of temptation
explain the choice data?
3. Connections in the demand for commitment devices
across domains:
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Are there correlations between goal setting and commitment in
the reimbursement program? Are there “commitment types”?
Road Map
1. Presentation of the weight loss challenge
2. Description of the experimental study
3. Commitment in the reimbursement program
4. Commitment through goal setting
5. Connections between 3. and 4.
Description of the weight loss challenge
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Experiment taking place in the context of an 8-week weight
loss challenge (March and April 2014).
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Participants are NYU faculty and staff members.
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Challenge inspired from the Biggest Loser TV show:
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The participant who loses the highest % of body mass wins
the contest.
Participants’ weight recorded at a private gym during
scheduled weigh-ins.
Participants benefit from an extensive support system:
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Free month membership at the private gym (month of March).
Free nutrition seminars and exercise classes.
Structure of the Experiment
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Participants recruited at the first weigh-in for an online study
on improving health through exercise and nutrition.
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Participants were asked to fill out a two-part online survey.
1. First part completed on the first week of the challenge.
2. Second part to be completed starting the last day of the
challenge.
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117 participants signed up for the study and 113 completed
the first survey out of 193 present at the first weigh-in.
Timeline and Structure of the Study
Data Collection
Period
Survey 1
(20 min)
March 4th March 11th 2014
Survey 2
(10 min)
April 29th May 6th 2014
Content of
the survey
- Part 1: Basic demographics
& questions about the challenge
- Part 2: Goal setting
- Part 3: Reimbursement program
- Questions about the Challenge and
personal performance evaluation
- Follow-up questions on Survey 1
- Self-Control measures
- Intertemporal choice tasks
Commitment in the Reimbursement Program (1)
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During the first survey, participants were introduced to a lunch
reimbursement program.
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10% of respondents drawn at random to be reimbursed
for all their lunch meals during the month of April.
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up to 20 meals and $15 per meal ($300 value).
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need to bring detailed lunch receipts with their name at the
last weigh-in.
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winners announced at the end of the challenge.
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Participants presented with various reimbursement options,
which differ in the range of foods covered by the
reimbursement.
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Reimbursement would cover one, two or three lunch categories.
Commitment in the Reimbursement Program (2)
Commitment in the Reimbursement Program (3)
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Elicited respondents’ preferences over the following set of
reimbursement options:
M := {G, O, R, GO, GR, OR, GOR}
Full preference ordering elicited with an incentive compatible
procedure:
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Participants randomly assigned a reimbursement option.
The odds of receiving a given option depended on its relative
ranking.
Rank
% chance of being drawn
1
2
3
4
5
6
7
35
30
20
10
3
2
0
Commitment in the Reimbursement Program (4)
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Participants also allowed to report indifferences between two or
more options.
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To incentivize indifferences, the ranking procedure made it
easier to report indifferences than strict rankings:
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Participants first selected all the options they wished to assign
rank 1.
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Then proceeded iteratively to assign all other ranks until the
list of options was empty.
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Controlled for order effects.
Options assigned the same rank received in expectation the
same chances of being selected.
Classifying menu preferences (1)
Now we can analyze whether agents exhibit temptation and
self-control through their menu choices.
1. For a standard DM (STD):
If A
B then A ⇠ A [ B
B
2. For a tempted DM with no self-control (GP-NSC):
If A
B then A
A[B ⇠B
3. For a tempted DM with self-control (GP-SC):
If A
B then A
A[B
B
Classifying menu preferences (2)
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All 3 cases are subsumed under the Set-Betweenness axiom of
Gul and Pesendorfer (2001), which states that:
If A ⌫ B then A ⌫ A [ B ⌫ B
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The model precludes strict preference for flexibility (FLEX):
If A
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B then A [ B
A
B
Also precludes cumulative temptations/guilt (CT-G):
If A ⌫ B then A
B
A[B
Connecting respondents’ choices to the GP model
1. Are contestants willing to restrict the range of foods they are
incentivized to eat?
2. How strict is their willingness to commit?
3. How often do their choice satisfy the Set Betweenness axiom?
And in which form?
Strict Preference versus Indifference
# of steps taken
to complete ordering
1
2
3
4
5
6
7
Total
% of participants
(N in brackets)
1.8
0.0
2.7
3.5
6.2
3.5
82.3
(2)
(0)
(3)
(4)
(7)
(4)
(93)
100 (113)
Coarseness of
the preference ordering
) full indifference
) strict ordering
Distribution of options by rank (1-4)
Distribution of options by rank (5-7)
Commitment versus flexibility
Preference
pattern
% of participants
(N in brackets)
Strict Commitment
{G } M for all M in M\{G }
15.0 (17)
{G , O}
Partial Commitment
M for all M in M\{G , O}
32.7 (37)
Preference for Flexibility
{G , O, R} M for all M in M\{G , O, R}
31.9 (36)
Other Preference Pattern
20.4 (23)
Total
100 (113)
How does the Set-Betweenness axiom perform?
Table : Commitment versus Flexibility in Pairwise Comparisons
% of participants per category (N in brackets)
Binary choice
{G }
{G }
{O}
{O}
{R}
{R}
{G } {O, R}
{O} {G , R}
{G , O} {R}
{G , O}
{G , R}
{G , O}
{G , R}
{O, R}
{O, R}
STD
FLEX
GP - NSC
GP - SC
CT - G
Total
6.4 (5)
1.0 (1)
0.0 (0)
66.7 (52)
23.5 (23)
23.4 (22)
0.0 (0)
1.0 (1)
2.1 (2)
19.2 (15)
69.4 (68)
70.2 (66)
7.7 (6)
5.1 (5)
4.3 (4)
100.0 (78)
100.0 (98)
100.0 (94)
4.8 (4)
3.4 (2)
3.9 (4)
36.9 (31)
36.2 (21)
33.7 (34)
0.0 (0)
0.0 (0)
0.0 (0)
48.8 (41)
48.3 (28)
59.4 (60)
9.5 (8)
12.1 (7)
3.0 (3)
100.0 (84)
100.0 (58)
100.0 (101)
4.2 (4)
3.6 (3)
4.0 (4)
31.2 (30)
79.5 (66)
32.3 (32)
2.1 (2)
0.0 (0)
0.0 (0)
49.0 (47)
10.9 (9)
53.6 (53)
13.5 (13)
6.0 (5)
10.1 (10)
100.0 (96)
100.0 (83)
100.0 (99)
How does the Set-Betweenness axiom perform?
Table : Distribution of menu preferences
Type of
decision maker
STD
FLEX
GP-NSC
GP-SC
CT-G
Total classified
Preference ordering
when M M 0
M ⇠ M [ M0
M [ M0
M
M
M
M
M0
4.4 (5)
M0
37.2 (42)
M [ M0 ⇠ M0
M [ M0
M0
M[
% of participants
(N in brackets)
0.0 (0)
M0
46.0 (52)
M0
7.1 (8)
94.7 (107)
Conclusions from the Reimbursement Program
1. Survey respondents were willing to restrict their choice.
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Most flexible option only favored 30-40% of the time.
2. However, respondents did not mostly favor strict commitment
to G and preferred to retain some flexibility.
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Most popular option was GO.
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Consistent with O not being a strong temptation.
3. The Set Betweenness axiom with self-control (GP-SC)
performs fairly well, in particular when it is to discard R.
Commitment through goal setting (1)
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All respondents were told that they would receive a $20 Whole
Foods gift card for completing the two-part study.
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They were offered the choice to receive their gift card only
contingent on the achievement of one or multiple self-set goals.
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All were attendance goals:
1. “Weigh-in goal”: Attend X follow-up weigh-ins during the
challenge (X 2 {0, 1, 2, 3})
2. “Gym goal”: Make Y gym visits during the free month
membership of March (Y 2 {0, 1, ..., })
3. “Wellness goal”: Attend Z Wellness events during the
challenge (Z 2 {0, 1, 2, 3, 4})
Commitment through goal setting (2)
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65% of respondents chose to commit through goal setting and
almost 50% chose to set multiple goals:
# of goals set
by a participant
% of participants
(N in brackets)
0
34.51
(39)
1
17.70
(20)
2
29.20
(33)
3
18.58
(21)
Commitment through goal setting (3)
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Distribution of goals by goal category
% of participants
(N in brackets)
Number X of follow-up weigh-ins
0
1
2
3
38.0
6.2
25.7
30.1
(43)
(7)
(29)
(34)
51.3
15.9
20.4
6.2
6.2
(58)
(18)
(23)
(7)
(7)
0
1
2
3
4
78.8
13.3
4.4
2.6
0.9
(89)
(15)
(5)
(3)
(1)
Total
100
(113)
Number Y of gym visits
0
1-5
6-10
11-15
16-20
Number Z of wellness events
Are there “commitment types”?
Table : Probit regression models of the propensity to set goals
(1)
(2)
(3)
(4)
-0.112
(0.119)
0.011**
(0.006)
-0.129***
(0.038)
-0.001
(0.001)
0.031**
(0.015)
-0.021
(0.042)
-
-0.059
(0.121)
0.011*
(0.006)
-0.126***
(0.037)
-0.001
(0.001)
0.028*
(0.015)
-0.032
(0.043)
-
-0.085
(0.120)
0.010*
(0.006)
-0.128***
(0.037)
-0.001
(0.001)
0.028*
(0.015)
-0.030
(0.042)
-
GO first
-0.079
(0.122)
0.012**
(0.006)
-0.113***
(0.036)
-0.001
(0.002)
0.035**
(0.015)
-0.006
(0.042)
-0.145
(0.151)
-
GOR first
-
0.231**
(0.090)
-
-
flex
-
-
-0.171
(0.109)
-
Observations
113
113
113
female
age
years of educ
starting weight
weight loss goal
goal confidence
G first
-0.174*
(0.105)
113
Conclusion
1. Provide new evidence of a demand for commitment:
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In a reimbursement program: almost 50% of respondents
strictly preferred to exclude R from their choice set.
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Through goal setting: 65% committed to at least one goal
and close to 50% committed to multiple goals.
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Across domains: overall 35% committed in both domains.
2. Provide the first axiomatic test of Gul & Pesendorfer (2001)
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46% of respondents mostly satisfy strict Set Betweenness
3. Policy implications:
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commitment programs incentivizing to eat healthy
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reward systems for goal achievement
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complementarities ) bundling of commitment devices

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