I’ll have what they’re having: a descriptive social norm increases choice for vegetables in students

Figures & data

Table 1. Participant descriptives of the overall sample and within each condition.

Characteristic	Overall, N = 142^1	fruit, N = 49^1	vegetable, N = 48^1	control, N = 45^1	p-value^2
Age	21.14 (4.41)	21.18 (5.35)	20.79 (3.41)	21.47 (4.29)	0.76
Gender					0.77
male	32 (23%)	10 (20%)	10 (21%)	12 (27%)
female	110 (77%)	39 (80%)	38 (79%)	33 (73%)
Living situation					0.25
alone	19 (13%)	6 (12%)	5 (10%)	8 (18%)
renting with others	13 (9.2%)	3 (6.1%)	6 (13%)	4 (8.9%)
student housing	31 (22%)	8 (16%)	15 (31%)	8 (18%)
with family	69 (49%)	25 (51%)	21 (44%)	23 (51%)
with partner	10 (7.0%)	7 (14%)	1 (2.1%)	2 (4.4%)
Study subject					0.14
health	5 (3.5%)	1 (2.0%)	3 (6.3%)	1 (2.2%)
humanities and social sciences	134 (94%)	48 (98%)	42 (88%)	44 (98%)
arts	3 (2.1%)	0 (0%)	3 (6.3%)	0 (0%)
BMI	22.27 (3.25)	21.73 (2.86)	22.55 (3.28)	22.56 (3.61)	0.36
Unknown	2	0	0	2

¹Mean (SD); n (%).

²One-way ANOVA; Fisher’s exact test.

Figure 1. Vegetable descriptive norm presented in the form of a sign-up sheet with choices made by fictional previous participants.

Figure 2. Plate with three fruits (apple, orange, persimmon) and three vegetables (artichoke, carrot, red pepper) presented to participants during the taste test.

Figure 3. Percentage of participants choosing fruit and vegetable baskets in the three different descriptive norm conditions.

Table 2. Simple effects and odds ratio (OR) of condition on choice.

		Descriptive norm
Outcome	Predictor	Vegetable vs. fruit	Vegetable vs. control	Fruit vs. control
Choice for vegetable	b (SE)	1.30 (0.49)	1.20 (0.49)	0.10 (0.55)
	p	.020	.038	.981
	OR [95% CI]	3.66 [1.46, 9.93]	3.30 [1.31, 9.00]	1.11 [0.37, 3.30]

Note. Odds Ratios (OR) for these effects were calculated based on logistic regression models. Tukey-adjusted p-values.

Table 3. Regression results for the effects of condition and food type on intentions and positive and negative taste expectations and experiences.

	Step 1			Step 2
		Contrast 1 Fruit vs. Vegetable	Contrast 2 Control vs. Fruit/Vegetable	Type: Fruit vs. Vegetable	Contrast1* Type	Contrast2* Type
Intentions	b (SE)	1.52 (3.33)	−2.00 (3.95)	−1.37 (8.35)	−0.29 (3.05)	− 4.39 (3.61)
	95% CI	−5.01, 8.05	−9.73, 5.74	−17.7, 14.9	−6.26, 5.68	−11.5, 2.68
	p	.650	.614	.872	.924	.224
	R^2 m, R^2 c	0.001, 0.383			0.002, 0.383
Positive taste expectations	b (SE)	0.50 (2.92)	−2.49 (2.71)	−13.9 (10.4)	−1.96 (2.17)	−0.14 (2.57)
	95% CI	−3.99, 5.00	−7.81, 2.83	−34.2, 6.38	−6.22, 2.29	−5.17, 4.90
	p	.827	.361	.228	.365	.957
	R^2 m, R^2 c	0.050, 0.310			0.050, 0.310
Negative taste expectations	b (SE)	−0.82 (2.62)	−0.75 (3.11)	-16.4 (4.11)	−2.54 (2.60)	3.13 (3.08)
	95% CI	−5.96, 4.32	−6.84, 5.35	-24.4, −8.32	−7.64, 2.55	−2.90, 9.16
	p	.755	.811	.007	.328	.310
	R^2 m, R^2 c	0.095, 0.306			0.096, 0.307
Positive taste experience	b (SE)	1.02 (2.44)	−3.39 (2.89)	-19.0 (7.20)	1.36 (2.13)	0.15 (2.52)
	95% CI	−3.76, 5.80	−9.05, 2.27	-33.1, −4.86	−2.81, 5.53	−4.78, 5.08
	p	.677	.242	.039	.523	.952
	R^2 m, R^2 c	0.097, 0.303			0.098, 0.303
Negative taste experience	b (SE)	1.34 (2.37)	−5.41 (2.80)	−1.29 (6.74)	−3.07 (2.56)	8.03 (3.03)
	95% CI	−3.30, 5.98	−10.9, 0.08	−14.5, 11.9	−8.09, 1.95	2.10, 14.0
	p	.573	.055	.854		.008
	R^2 m, R^2 c	0.007, 0.259			0.010, 0.263

Note. We used contrast coding to compare the fruit norm (−0.5) to the vegetable norm (0.5) and the control norm (−0.5) to both the fruit (0.25) and vegetable (0.25) norm conditions. Pseudo-R-squared for Generalized Mixed-Effects models were calculated using the MuMIn package (Bartoń, 2022). R² _m (marginal) by fixed effects and R² _c (conditional) is the variance explained by both fixed and random effects. Significant effects are shown in bold.

Bartoń, K. (2022). MuMIn: Multi-Model Inference [Computer software]. https://CRAN.R-project.org/package=MuMIn

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Data availability statement

The data that support the findings of this study are openly available on the Open Science Framework at https://osf.io/d4c8y/?view_only=a64d519e70a94c63bc5b3aa04373fed5.