Mycoflavour consumer study

Last registered on October 28, 2025

Pre-Trial

Trial Information

General Information

Title
Mycoflavour consumer study
RCT ID
AEARCTR-0017108
Initial registration date
October 26, 2025

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
October 27, 2025, 9:16 AM EDT

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

Last updated
October 28, 2025, 4:29 AM EDT

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

Locations

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Primary Investigator

Affiliation
Technical University of Denmark

Other Primary Investigator(s)

PI Affiliation
Copenhagen Business School
PI Affiliation
University of Copenhagen
PI Affiliation
Technical University of Denmark, University of Copenhagen

Additional Trial Information

Status
In development
Start date
2025-10-27
End date
2026-02-28
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
Abstract
This study examines how people make choices about sustainable food products, focusing on what motivates them and how they perceive product characteristics. We are interested in understanding whether health-related or climate-related messages are more effective in encouraging consumers to choose plant-based foods such as meat and milk alternatives. We will test how these messages influence people’s willingness to pay for sustainable products and how this depends on their personal values and motivations related to health and the environment.
In addition, we study how the level of food processing affects consumer choices between beef and plant-based burgers. People often see plant-based alternatives as more processed or less natural, which may reduce their appeal. In a choice experiment, we will explore how consumers balance different attributes, including main ingredient (beef or plants), processing level, ecological footprint, saturated fat, and price.
Both parts of the study will use online experiments with participants recruited from the Danish population. The results will help us understand how consumers think about sustainability and health in their food choices and provide insights for developing and promoting more appealing sustainable food options.


External Link(s)

Registration Citation

Citation
Bøye Olsen, Søren et al. 2025. "Mycoflavour consumer study." AEA RCT Registry. October 28. https://doi.org/10.1257/rct.17108-1.1
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Experimental Details

Interventions

Intervention(s)
In the first part of the study (tasks 1 and 2), we have two treatment groups and one control group. In the treatment groups, sustainable alternative food products will be presented either with a climate or a health argument, whereas in the control group only a general product description will be provided. Conventional food products always will only be presented with a general product description.
In the second part of the study (task 3), there are no treatment variations, but a discrete choice experiment.
Intervention Start Date
2025-10-27
Intervention End Date
2025-12-31

Primary Outcomes

Primary Outcomes (end points)
Study part 1: Willingness to pay (Becker-De-Groot-Marschak and Staircase Method)
Becker-De-Groot-Marschak: In task 1, the willingness to pay is measured by asking participants to indicate the maximum price they are willing to pay for each product. When indicating a number, participants are limited to the range of a provided budget of DKK 70 for meat products and DKK 40 for milk products. A randomly drawn reservation price in the range of 0-40 for milk product/ 0-70 for meat products will determine if participants can buy the product. For the participants, the reservation price is unknown when indicating willingness to pay.
Staircase Method: The willingness to pay in task 2 is measured by taking the highest price level at which the alternative product was chosen in comparison to the conventional product in our staircase measure (see description in Experimental Design). The WTP corresponds to zero if the individual only chooses the conventional product in all scenarios and to the highest price if the individual only chooses the alternative product in all scenarios (thus, bound to a range of DKK 18-40 DKK for milk products/ DKK 30-70 for meat products). We obtain one value per product comparison per individual.

Study part 2: In the discrete choice experiment (task 3), we measure choice as the choice of one out of three alternatives and an opt-out option (no buy).
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Comprehension questions
Manipulation check
Salience climate and health treatment

Ratings of taste expectations
Knowledge of products and previous purchase

Climate motivations
Efficacy beliefs, self-identity, present intention/ behavior, future intention, self-efficacy)

Health motivations
Efficacy beliefs, self-identity, present intention, future intention, self-efficacy)

Social preferences
Donation task
Sharing willingness

Time preferences
Intertemporal willingness

Food neophobia

Diet
Diet type
Frequency of meat and fish consumption

Importance ranking

Knowledge about a healthy diet

Knowledge about a climate-friendly diet

Taste preferences

Burger eating habits
Frequency of consumption
Context of consumption
Burger types consumed

Meat attachment
Meat attachment
Social norms of meat eating
Descriptive social norm
Injunctive social norm

Relevance of protein for WTP

Social norms and personal norms of processed food consumption
Social approval
Personal norm

Sociodemographics:
Age
Household net income
Education
Occupation
Region
Municipality
Meta-data: Time and clicks, language
Register data
Secondary Outcomes (explanation)
Comprehension questions: Prior to task 1 and 2, we ask two questions each that must be passed to continue, with 5 possible rounds. After task 3, we ask participants to tick from a MC-list all the attributes that we did vary in the DCE, with additional options that we were not among the attributes.
Manipulation check, for conventional burger product and more novel sustainable alternative burger product:
In Tasks 1 and 2 that you just completed, what information was provided along with the product you see here? Please pick one of the possible statements below:
Popular choice due to its lower price.
Sustainable choice due to less CO2 emissions and more efficient land use.
Fair choice due to production under good working conditions.
Healthy choice due to less saturated fat and more fiber intake.
None of these statements was shown.

Salience climate and health treatment:
“You have read information about some of the food items, e.g., [treatment information text inserted here]. Were you aware of this information before participating in the survey?” (yes/no)

Ratings of taste expectations of the products from task 1 and 2 (on a scale from 1=does not taste good at all to 10=tastes very good)
Knowledge of products and previous purchase (yes/no).

Climate motivations (Efficacy beliefs, self-identity, present intention, future intention, self-efficacy), 7-Point-Likert scale from “strongly disagree” to “strongly agree” except for self-efficacy
Efficacy beliefs: “I believe that my food choices have an influence on climate change.”
Self-identity: “I think of myself as someone who generally thinks carefully about the climate consequences of my food choices.” and “I think of myself as the sort of person who is concerned about the long-term climate effects of my food choices.” We will use the mean of these two items on the individual level.
Present intention/behavior: “I make an effort to eat a diet that is climate friendly.”
Future intention: “I intend to consume more climate friendly foods in the future.”
Self-efficacy: “How confident are you generally in making food choices that reflect climate awareness? Please indicate in percent (0 = not at all confident; 100 = completely confident).”
Construction: Items can be averaged into subscales (e.g., efficacy, identity, intentions) or one composite climate motivation index. Confidence is treated as a separate continuous variable (0–100).
Health motivations (Efficacy beliefs, self-identity, present intention, future intention, self-efficacy), 7-Point-Likert scale from “strongly disagree” to “strongly agree” except for self-efficacy
Efficacy beliefs: “I believe that my food choices have an influence on my health”
Self-identity: “I think of myself as someone who generally thinks carefully about the health consequences of my food choices.” and “I think of myself as the sort of person who is concerned about the long-term health effects of my food choices.” We will use the mean of these two items on the individual level.
Present intention/behavior: “I make an effort to eat a diet that is healthy.”
Future intention: “I intend to consume more healthy foods in the future.”
Self-efficacy: ”How confident are you generally in eating healthily? Please indicate in percent (0 = not at all confident; 100 = completely confident).”
Construction: Items can be averaged into subscales (e.g., efficacy, identity, intentions) or one composite health motivation index. Confidence is treated as a separate continuous variable (0–100).

Social preferences
Donation task: “Imagine the following situation: you won 7.500 DKK in a lottery. Considering your current situation, how much would you donate to charity? (Values between 0 and 7500 are allowed)”.
Sharing willingness: “How do you assess your willingness to share with others without expecting anything in return when it comes to charity?”, scale from 0= “completely unwilling”-10=”very willing”.
Construction: Continuous measure of altruism via donation share (donated amount / 7,500).
Secondary measure via 0–10 sharing willingness

Time preferences
Intertemporal willingness: “In comparison to others, are you a person who is generally willing to give up something today in order to benefit from that in the future or are you not willing to do so?”, scale from 0= “completely unwilling”-10=”very willing”.
Construction: Higher values indicate more patience or future orientation.

Food neophobia
“How much do you agree or disagree with each of these statements?”, 7-Point Likert Scale from “strongly disagree” to “strongly agree”
If I don’t know what is in a food, I won’t try it.
I don’t trust new foods.
I eat almost anything. (reverse-coded)
Construction: average of items (reverse code last item); higher scores = greater neophobia.

Diet
Diet type: “What description best depicts your current diet?”, single-choice categorical from
“I eat everything (including meat, fish, dairy products etc.)” to “I eat vegan”.
Frequency of meat and fish consumption: “Please indicate the frequency of your meat and fish consumption.”, ordinal scale from “daily” to “only on special events, like celebrations”, dependent on being type 1-3.
Construction: categorical or ordinal variable, can be collapsed into plant-based vs. omnivorous group.

Importance ranking
“What are the most important dimensions you consider when making food choices? Please rank by dragging the items up and down. 1 = most important, 5 = least important”
Taste
Price
Healthiness
Sustainability
Convenience (it is easily available)
Construction: Top 3 ranked items

Knowledge about a healthy diet
“Think about the following main fillings/toppings of a sandwich. Rank these fillings from the most healthy (1st) to the least (5th) assuming a similar quantity and quality.”
Egg
Fish filet (breaded)
Roasted beef
Falafel (Chickpeas)
Chicken breast
Construction: Accuracy score compared to nutritional reference ranking (e.g., falafel > fish > egg > chicken > beef).

Knowledge about a climate-friendly diet
“Think about the following main fillings/toppings of a sandwich. Rank these fillings from the most climate friendly (1st) to the least (5th) assuming a similar quantity and quality.” Answer options as in previous question.
Construction: Accuracy score compared to scientific benchmark (e.g., falafel > egg > chicken > fish > beef).

Taste preferences
“Think about the following main fillings/toppings of a sandwich. Rank these fillings from the most tasty (1st) to the least (5th) assuming a similar quantity and quality.” Answer options as in previous question.
Construction: Used descriptively or to control for taste bias toward plant vs. meat products.

Burger eating habits
Frequency of consumption: “How often do you normally eat burgers?”, “never” to “several times per week“
Context of consumption: “Under which circumstances do you eat burgers? You can choose several answers.”, multiple choice of different contexts (e.g. at home, restraurant, with friends and family etc.)
Burger types consumed: “What kind of burgers do you normally consume? You can choose several answers.”, multiple choice of different burger types (e.g., beef burger, homemade burger, soy-based burger etc.)
Construction: Variables can be summarized as frequency, context diversity, and plant-based burger experience.

Meat attachment
Meat attachment
“How much do you agree or disagree with each of these statements on meat eating?”, 7-Point-Likert Scale from “strongly disagree” to “strongly agree”
“I love meals with meat.”
“By eating meat I'm reminded of the death and suffering of animals.” (reverse-coded)
“It is undoubtedly natural to consume meat.“
“I find it hard to picture myself not eating meat regularly.”
Social norms of meat eating
Descriptive social norm: “Most of the people I know eat meat on a regular basis.” and
Injunctive social norm: “Most of the people I know are more likely to gain approval from others if they eat meat rather than follow a vegetarian diet.”
Construction: We will use the mean of these items on the individual level; higher = stronger attachment to meat. Subdimensions possible (hedonism, dependence, social norm).

Relevance of protein for WTP
“How important is protein content when deciding how much you would pay for a food item?”, 5 Point Likert Scale from “not at all important” to “very important”
Construction: Ordinal variable; higher values = greater importance of protein for valuation.

Social norms and personal norms of processed food consumption
“How much do you agree or disagree with each of these statements on food processing? Processing relates to how the product is produced. Processing levels vary with adding ingredients or physically altering the food, like grinding or heating it.”, 7-Point-Likert scale from “strongly disagree” to “strongly agree”.
Social approval: “Most of the people I know are fine with eating processed food.”
and “Most of the people I know think it is safe to consume processed food.”
Personal norm: “I feel I should be cautious with the amount of processed foods I consume.”
(reverse-coded if constructing acceptance index).
Construction: Average of first two = social approval, last item separately as personal caution or personal norm.

Sociodemographics:
Age: open numeric input
Household net income: 5 categories (0–20k to >80k DKK)
Education: categorical (primary to Master’s/PhD)
Occupation: categorical (unemployed, student, employed, etc.)
Region: 5 Danish regions
Municipality: region-specific dropdown lists
Construction: Direct categorical and continuous variables; can be coded to national statistical categories.
We will apply for register data from Statistics Denmark, such as demographic data, income, occupation, education and household size etc.
Meta-data: Time and clicks per page

Experimental Design

Experimental Design
We conduct an online study, sampling participants via digital post invitation, in Denmark. The online study consists of two parts, a behavioral experiment and a discrete choice experiment.
In the first part of the study, participants are divided into three experimental groups, each exposed to different information about the products: a climate-focused argument, a health-focused argument, or no additional information (control group). Participants initially indicate their individual willingness to pay for nine different products. They then complete five rounds of binary choices between two products with varying prices. The study employs an experimental design, incorporating a between-subjects factor (information condition: climate, health, or control) and two variations on product level, that we vary within subjects: product type (conventional, more novel sustainable alternative, more common sustainable alternative) and product category (burger patty, minced meat (alternative), and milk (alternative)).
In the second part of the study, all participants are part of a discrete choice experiment. Participants are split into three groups, which vary in the presented choice scenarios. The experiment is a hypothetical scenario, where participants are asked to imagine they want to make burgers at home and are at the supermarket to buy a patty. Across 8 trials, in each scenario, they are presented with three potential burger patties, which vary in attributes across trials, and an opt-out option. The attributes are main ingredient (2 levels), processing level, ecological footprint, saturated fat (all three levels), and price (4 levels). In each trial, participants choose which burger patty they would rather buy (or they can opt out).
At the end of the survey, participants answer questions on their attitudes and motivations related to food consumption, and socio-demographics (see secondary outcomes).
Experimental Design Details
Not available
Randomization Method
Participants will be randomly assigned to each treatment group using the Qualtrics randomization feature (simple randomization), where each participant will be assigned to one of three blocks. The same procedure will be used to randomize participants into three blocks for the discrete choice experiment . Orders of products in task 1 and comparisons in task 2, as well as the order of choice scenarios in the DCE will be randomized.
Further, we randomize potential participants into three reminder groups prior to sending out invitations (no reminder, one reminder, two reminders). This is performed with the Python package Numpy random choice function.
Randomization Unit
Randomization will be conducted at the individual level.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
0
Sample size: planned number of observations
N = 3000
Sample size (or number of clusters) by treatment arms
n = 1000 per group and n =1000 per block (separate of each other)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Task 1: We used the software package G*Power to estimate the sample size needed to find our proposed main effect of group differences. Based on repeated-measures ANOVA and an effect size of 0.02 for a three-way interaction between group, product category and type, a significance level of 0.05 and a power of 0.8, and assuming a correlation between observations of 0.5, we yield a minimum sample size of 2679. However, WTP might not be normally distributed. To take this into account, and in order to determine sample size needed to detect the proposed interactions with mechanism variables, we run simulations in R. To reach a power of at least 0.8 for all hypothesized effects given these are between 0.01-0.15, we estimate a sample size of N = 2400 . Task 2: We used the software package G*Power to estimate sample sized needed to find our proposed main effect of group differences. Based on a repeated-measures ANOVA and an effect size of 0.03 for a three-way interaction between group, product category and type, a significance level of 0.05 and a power of 0.8, and assuming a correlation between observations of 0.5, we yield a minimum sample size of 1194. To consider that WTP might not be normally distributed, and in order to determine sample size needed to detect the proposed interactions with mechanism variables, we run simulations in R. To reach a power of at least 0.8 for all hypothesized effects given these are between 0.01-0.15, we estimate a sample size of N = 2400. DCE: Based on our efficient design for the DCE we created using Ngene, N = 174 participants should be sufficient to find the hypothesized effects. However, to explore heterogeneity, a bigger sample size is preferable, and in similar studies sample sizes succeeded 1000 participants.
IRB

Institutional Review Boards (IRBs)

IRB Name
DTU MAN Research Ethics Committee
IRB Approval Date
2025-08-26
IRB Approval Number
DOCX 25/1005539-5
Analysis Plan

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