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