Emotional priming for sustainable consumption? Differential effects on valuation of labelled chocolate

Last registered on May 04, 2022


Trial Information

General Information

Emotional priming for sustainable consumption? Differential effects on valuation of labelled chocolate
Initial registration date
December 10, 2021

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
December 10, 2021, 3:12 PM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
May 04, 2022, 6:23 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

University of Göttingen

Other Primary Investigator(s)

PI Affiliation
University of Göttingen
PI Affiliation
German Institute for Global and Area Studies (GIGA)
PI Affiliation
German Institute for Global and Area Studies (GIGA)

Additional Trial Information

On going
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Current food choices are unsustainable: most food products have social and environmental consequences that harm current and future generations worldwide. Recent studies analyzed the determinants driving sustainable food choices and experimentally tested ways to increase consumers’ willingness-to-pay for sustainability certifications. Thereby, evidence is scarce of how to reach the average consumer effectively. Insights into the potential of emotionally primed information - as commonly used in brand marketing and donation calls - suggest that the use of emotions serves as an efficient tool of mass communication by reaching the average consumer, not only a niche market. Thus, the effects of linking information to emotional priming on the greater valuation of sustainable products are not well understood. To answer whether emotional priming in information provision increases consumers’ valuation of sustainable foods, we conduct an online experiment with 3,500 German consumers. We randomly assign information treatments related to either (1) social responsibility or (2) environmental sustainability. Each information treatment is delivered (a) with an emotional primer and (b) without. Using a discrete choice experiment and random parameters multinomial logit models, we estimate the effects of emotional priming on consumers’ willingness-to-pay for sustainability attributes, by sustainability objectives and sustainability claims in the short-and medium-term. We contribute to the existing literature in three ways by considering long-term treatment effects, social and environmental sustainability, and different product alternatives. Our findings are relevant for policymakers, NGOs, and companies because it provides insights for social marketing campaigns to promote sustainable consumption patterns.
External Link(s)

Registration Citation

Iweala, Sarah et al. 2022. "Emotional priming for sustainable consumption? Differential effects on valuation of labelled chocolate." AEA RCT Registry. May 04. https://doi.org/10.1257/rct.8689-2.0
Sponsors & Partners

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Experimental Details


Our randomized controlled trial includes four information treatments about the coca sector and no control group. The format of the treatments are short videos which consist of several animated slides. We designed the videos in line with formats commonly used on social media like Instagram. Our four treatments are distinct because they differ in sustainability objective as well as emotional prime.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
The most important outcome to test the stated expectations is the consumers’ marginal WTP for each one of the varying sustainability attributes. The marginal WTP corresponds to the marginal rate of substitution (MRS) between one attribute and price.
Primary Outcomes (explanation)
As we are using the random parameters multinomial logit (RPL) model, we cannot use a simple ratio to estimate the marginal WTP. Instead, we reparametrize the RPL to the WTP space by using maximum simulated likelihood like in Train and Weeks to derive marginal WTP of each attribute (or better marginal WTP for no certification or no claim to a certification or a claim).

Secondary Outcomes

Secondary Outcomes (end points)
We consider four other outcomes: utility, willingness-to-purchase, recall attention frequency of certified and uncertified sustainability claims on products, and emotions triggered by the treatments.
Secondary Outcomes (explanation)
We will simulate the utlity of the chosen attributes using the RPL model.
A supplementary outcome is the willingness-to-purchase, a factor based on the self-reported likelihood or willingness of purchasing of one of the following four types of chocolate each: either with Fairtrade certification, Rainforest alliance certification, claim regarding social responsibility, or claim regarding environmental sustainability. We adapt the measure of self-stated likelihood or willingness to purchase Fairtrade chocolate in the future from Hansen et al. (see attached document). We also adjust the measure to a seven-point Likert-Scale. We choose to have an option of indifference despite a possible framing effect to ensure that we allow for all possible preferences of the participants. We will perform principal component analysis in order to narrow down the statement batteries to the core of the concept.
For the outcome of recall attention frequency we integrate a 14-day recall question by asking, how often they have paid attention to a number of claims or certifications in the last 14 days whilst shopping, e.g. the Nutri-Score and GMO-free labels. We include certifications and claims not related to our study so that we do not prime participants towards the certifications of interest. The categorical outcomes include seven levels of frequency.
Lastly, we capture how participants feel after watching the videos at the end of the questionnaire in the first wave and in a similar manner in the second wave. For that purpose, we employ the Discrete Emotions Questionnaire by Harmon-Jones et al. that measures anger, disgust, fear, anxiety, sadness, desire, relaxation and happiness via four items each. We will perform principal component analysis to establish continuous factors of eight groups of emotions that are based on each four components. Based on the findings in our pilot study, we will reduce the number of emotions asked for in the final survey.

Experimental Design

Experimental Design
To answer whether emotional priming in information provision increases consumers’ valuation of sustainable foods, we collect panel data of German consumers via online surveys. We randomly assign four information treatments that differ in sustainability aspect or addition of emotional primes (pictures). We employ a discrete choice experiment and answers related to self-reported consumption behavior to measure the consumers’ valuation of chocolate bars.
Experimental Design Details
The data collection will be conducted by the panel provider respondi between May and July 2022. We conducted a pre-test with the same quota and the same panel provider in January 2022 for about one week.
The first survey wave will take place in May to June 2022 for about two weeks, and the second survey wave - about two weeks later - will take place in June to July for about three weeks.
For the discrete choice experiment, we offer choices with four varying sustainability attributes at two levels and four levels of the attribute price for a 100-g bar of chocolate with unknown brand and flavor. The sustainability attributes include the presence of the label Fairtrade, the label Rainforest Alliance, a claim related to social responsibility, or a claim related to environmental sustainability.
Since we are only interested in the main effects of the sustainability attributes, we use a fractional factorial design. Due to the large number of choice sets, we assign the participants randomly to one of seven blocks of choice sets that are fixed groups of choice sets. To counteract order effects, we vary the order of the choice sets and the order of the choices within each set. The participants are each exposed to four choice sets in which they are asked to make a choice between two chocolate bars. Respondents have the option to indicate that they would not buy any of the chocolate bars as a third option.
Randomization Method
The participants will be randomly selected among the pool of available participants in a panel provider’s respondent pool. Invitations to participate will be sent out according to the quota settings for age, gender, income and education in order to match the population in Germany in these characteristics.
Once the participants have agreed to take part in the survey and match the quota, their assignment to the treatment occurs randomly. The software UniPark for designing the online questionnaire will randomize the treatments, choice set blocks, and choice set order.
Randomization Unit
The randomization of the treatment is on the individual level.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
3,500 participants
Sample size (or number of clusters) by treatment arms
875 participants in each of the four treatment arms
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
The sample size is terminated by the available funds, 3,500 participants, i.e. 875 participants in each of the four treatment arms. As our focus lies on the outcomes of the discrete choice experiment, we only concentrate on the power calculations for the utility outcomes. According to the rule of thumb by Johnson and Orme, this sample size should be a large enough sample to detect statistically significant main effects. In our case with c= 4 (largest number of levels of any attribute), t= 4 (number of choice tasks), and a=3 (number of alternatives), N needs to be larger than 167.

Institutional Review Boards (IRBs)

IRB Name
Ethics committee of the University of Göttingen
IRB Approval Date
IRB Approval Number
Analysis Plan

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Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials