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A social norms approach to encouraging healthier eating
Suzanne Higgs
School of Psychology
University of Birmingham, UK
We are encouraged to eat healthily
What is the evidence this works?• Public information campaigns and educational measures
(Capacci et al. 2012)• Strong evidence on awareness/attitudes• Small impact on behaviours
• Health message and labelling at point of purchase
(Skov et al. 2013)• Outcomes not consistent• Labelling foods as ‘healthy’ has been associated with being less
tasty
Alternative approaches are needed
Obesity spreads though social ties
Chistakis and Fowler (2007)• Framingham Heart Study
• 5124 subjects • 12,067 in social network• Longitudinal Social network
mapped/modeled
• Increased chance of becoming obese:• 57% if friend became obese• 40% if sibling became obese• 37% if spouse became obese
Eating is a social activity
Social influences on eating are powerful
Goldman, Herman and Polivy, 1991
Social processes and eating
• Modelling• Imitate others to make a good
impression and be liked (Roth et al. 2001)
• Perceived norms• The behaviour of others is a signal for
appropriate behaviour (Cialdini 1988)
Modelling and impression management
• More modelling in unsociable versus sociable context (Hermans et al. 2009)
• Women eat lightly with an attractive man (Mori et al. 1987)
Modelling and impression management
• 50 female students• mean age = 19.1 years, s.d = 1.0• healthy BMI 21.1, s.d = 2.6
• Manipulation:• Priming of social acceptance• Word search involving social acceptance or neutral words
(Carvallo & Pelham 2006)
• Social interaction with a confederate who ate 16 pieces of popcorn
Participant characteristics and food intake
Primed condition (n = 25)
Neutral condition (n = 22)
BMI 21.1 (2.7) 21.1 (2.4)
Hunger (0–10 cm scale) 4.8 (2.4) 4.2 (2.8)
Restraint (0–21 scale) 7.8 (5.3) 7.0 (5.4)
Degree of matching to confederate 5.32 (8.4) −0.59 (9.6)*
Robinson et al. 2011
Modelling and food choice• 105 female students
• mean age = 19.9 years, s.d = 2.6• healthy BMI 21.9 s.d = 3.3
Buffet lunch (mood and food study): sandwich, pastries, crisps, Carrot sticks, Cherry tomatoes and rice cakes
• Manipulation:• “Healthy” confederate• “Unhealthy” confederate• Choose alone
Method• On arrival participants waited alone (control condition) or with a
confederate who was instructed to arrive in waiting room 5 minutes early
• Baseline hunger and personality measures completed together
• Shown to buffet and asked to select a lunch
• Confederate makes choices seen by the participant
• Confederate and participant led to separate rooms to eat lunch
• Participant rates enjoyment of lunch items, completes restraint scale, asked to guess aims and has weight and height measured
Results: Participant characteristics
Condition Control Healthy Confederate
Unhealthy Confederate
Age (years) 20.7 (0.5) 19.7 (0.5) 19.4 (0.4)
BMI 21.9 (0.6) 21.7 (0.6) 22.2 (0.6)
Restraint 7.1 (1.0) 7.5(0.9) 8.3 (0.9)
Baseline Hunger (0-10 cm)
6.6 (0.4) 5.8 (0.3) 5.9 (0.3)
Total calorie intake at buffet
243.8 (16.8) 237.8 (15.7) 249.7 (15.3)
Robinson et al. British Journal of Nutrition 2013
Results: food choice
Food type
Sandwich Energy dense Low energy dense
Am
ou
nt
ch
ose
n (
g)
0
5
10
15
20
25
30
35
40
45
ControlHealthyUnhealthy
*
Robinson et al. British Journal of Nutrition 2013
Discussion
• Choice of low energy sense foods was reduced when there was an “unhealthy” confederate present
• Suggests that participants were willing to consume low energy dense food but this was abandoned in the presence of an “unhealthy” confederate
• Unhealthy eating models may undermine attempts to increase or maintain consumption of low energy dense foods
Conclusions 1Food intake and choice are influenced by social context at the time of eating/choosing
Impression management is one process that may mediate the effects of social context on intake
Friendship networks may be harnessed to promote healthier eating
Perceived norms
• People tend to use the behaviour of others to guide behaviour
• Norm effects are observed even when individuals believe they are not being watched
Intake norm
Low norm No norm High norm
NU
mbe
r of b
iscu
its e
aten
0
1
2
3
4
5
6
Robinson et al. Appetite 2013
Social norms approach to behaviour change
A participatory process
Is not moralistic in tone
Does not use scare tactics
(McAlaney et al., 2010)
Messages included in a social norms intervention present information about healthy norms of a population back to that population
Social norms approach to healthy eating campaigns
1) Meet experimenter 1. Complete demographics and given flyer and poster
2) Read posters and flyers
3) Rate flyer and poster for clarity etc.
4) Taken to new room and meet experimenter 2
5) Complete mood ratings, including hunger
6) Taken to buffet, select food and eat alone
7) Mood ratings, restraint scale, guess aims of study, weight and height
8) Measurement of habitual vegetable intake (how many portions of veg did you eat yesterday) and manipulation check
A social norm increases vegetable intake in low consumers
Habitual vegetable consumption
Low consumers High consumers
Ve
geta
ble
s co
nsum
ed
0
20
40
60
80
100
Health controlSocial Norm
*
Robinson et al. in press, Health Psychology
Habitual fruit and vegetable consumption
Low consumers High consumers
Fru
it a
nd v
eg
eta
ble
s co
nsum
ed
(g
)
0
20
40
60
80
100
120
Health controlInjunctive normDescriptive norm
A social norm increases fruit and vegetable intake in low consumers
*
Robinson et al. in press, Health Psychology
Group
Control Health Social
Ca
lori
es
0
50
100
150
200
250
300
350
*
*
What are the mechanisms?
• Correction of misperceptions?
• Conformation to expected behaviour?
• Change in expected liking and actual liking?
Medial orbitofrontal cortex activation
• Expose participants to social information about liking for orange juice
• Neutral or negative information from an in-group (female university students)
• Negative information from an out-group (overweight male university students)
1) Rate other students’ liking for orange juice
2) Read survey results of liking for orange juice
Negative in-group condition
3) Rate how much other students like orange juice (manipulation check)
4) mock personality measures
6) Asked to complete questionnaire for a different study
7) Rate liking for 6 foods including orange juice and apple juice
8) Write down aims and debrief
Neutral in-group condition
Negative out-group condition
Liking ratings: 0-10 cm line scale, anchors
‘don’t like at all’ and ‘like very much’
Neutral in-group condition, n =
28
Negative in-group condition, n =
27
Negative out-
group condition, n =
29Change in beliefs about other students’ orange
juice liking
- 0.2 (0.9)
-3.6 (2.0)
-3.0 (2.4)
Self-beliefs aboutorange juice liking
7.3 (2.3)
6.0 (2.7)*
7.6 (2.3)
Self-beliefs aboutapple juice liking
6.4 (2.6) 6.4 (3.1) 7.0 (2.7)
Conclusions 2
Perceived social norms can affect food choice and intake
One underlying mechanism may be an effect on liking expectations
Current work• Can “liking norms” be exploited to improve food choice?
• How long lasting are the effects of norms?
• Do the effects work in a real world context?
• Are they effective for different types of consumers?
Overall conclusions
Social context is a powerful influence on food intake and choice
Interventions that are based on social influences could be effective in improving dietary habits
Acknowledgements
Collaborators:
Paul Aveyard Oxford University Eric Robinson, Liverpool University, Peter Herman Toronto University