Ingroup Bias in Regulatory Enforcement and Implications for Food Integrity

Intervention 1: Control
In the control condition, participants assigned to the Food Standards Inspector role will complete the monitoring experiment without receiving a professional impartiality reminder. They will receive the standard experimental instructions describing their assigned colour group, role and tasks.

Intervention 2: Professional impartiality reminder
In the professional impartiality reminder condition, participants assigned to the Food Standards Inspector role will complete the same monitoring experiment as the control group. In addition to the standard instructions, inspectors will receive a professional impartiality reminder based on the principle of impartiality in ISO/IEC 17020. The reminder will be presented before the first monitoring allocation decision and will be displayed once more as a pop-out at a randomly selected round between Rounds 4 and 10. Participants must acknowledge the pop-out reminder before proceeding with the monitoring allocation decision.

2026-08-01

2026-12-31

Number of monitoring units allocated to each food producer in each round.

The primary outcome will be the number of monitoring units allocated by a Food Standards Inspector to each Food Producer in each round. The primary analysis will compare monitoring units allocated to ingroup and outgroup producers and assess whether the professional impartiality reminder reduces any difference in monitoring allocation between the two groups. We expect inspectors to allocate fewer monitoring units to ingroup producers than to outgroup producers. We also expect the ingroup–outgroup difference in monitoring allocation to be smaller in the professional impartiality reminder condition than in the control condition.

1. Undetected non-compliance (binary)
2. Monitoring allocation updating following non-compliance detection

1.Undetected non-compliance will be measured as a binary outcome equal to 1 when a Food Producer misreports a food quality grade and not detected due to no monitoring allocated, and 0 otherwise. Exploratory analyses will examine whether the likelihood of undetected non-compliance differs between ingroup and outgroup producers.

2. Monitoring allocation updating will be measured as changes in the number of monitoring units allocated in subsequent rounds following the detection of non-compliance. Exploratory analyses will examine whether inspectors update their monitoring allocations differently after detecting ingroup versus outgroup non-compliance.

In addition, the demographic information and post-experiment survey measures will also be collected, including risk attitude, role engagement, and group identity measures. For Food Standards Inspectors, this includes beliefs about ingroup and outgroup compliance rates, trust in ingroup producers, suspicion towards outgroup producers, and professionalism norms. For Food Producers, this includes beliefs about honest reporting as a social norm, perceived leniency from ingroup inspectors and scrutiny from outgroup inspectors, guilt associated with misreporting, and compliance pressure. These measures will be used descriptively and in exploratory analyses to examine potential mechanisms and sources of behavioural heterogeneity.

Participants will be recruited through Prolific Academic to take part in a multiplayer online experiment programmed in oTree. Eligible participants must be 18 years of age or older, fluent in English, have a Prolific approval rating of at least 95%, and have normal colour vision to distinguish the colours used in the experiment. All eligibility criteria will be screened using Prolific's prescreening filters before participants can access the study. Participants who meet the eligibility criteria and provide informed consent will complete a brief video-based attention check. Participants will be given a maximum of two attempts to answer the attention check correctly before proceeding to the experiment.

Procedures:
1. 20 participants will join the online experiment session on Prolific Academic. Each session will be randomly assigned to either the control condition or the professional impartiality reminder condition.
2. Participants will provide their consent and complete a brief video-based attention check.
3. Upon completion, participants will remain on a waiting page until all participants have arrived and are ready to begin the experiment. If not all participants arrive within 10 minutes, the session will not proceed, and participants who did arrive will receive a fixed compensation payment for their time.
4. Participants will be randomly assigned to one of two arbitrary colour groups (Blue or Green). They will be informed of their assigned group, which will remain fixed throughout the session.
5. Participants will then be randomly assigned to undertake the role of either Food Standards Inspector or Food Producer.
6. Participants will receive role-specific instructions, earnings and complete a role-specific comprehension check before proceeding to their task.
7. The Inspector’s task is to allocate monitoring units across four Food Producers, two of which are their ingroup.
8. The Food Producers’ task is to report their food quality grade. Reporting higher than their actual food quality grade increases their earnings, but there are risks of being monitored for non-compliance. None, some or all Food Producers' reporting activities will be monitored in each round.
9. The experiment consists of 10 rounds. Each Inspector will be matched with four Food Producers comprising two ingroup and two outgroup producers. Participants will be randomly rematched using a stranger matching design in the subsequent rounds. Although repeated Inspector–Food Producer encounters may occur by chance, Food Producers will be assigned temporary identities in each round to prevent producer-specific reputation formation.
10. At the end of each round, participants will receive their round result.
11. After completing all ten rounds, one round will be randomly selected for earnings. Participants will received earnings from the selected round and the participation fee.
12. Participants will complete a post-experiment survey comprising demographic questions, risk attitude, group identity measures, and role-specific attitudinal measures.

Not available

Randomization is programmed and implemented in oTree using its built-in random assignment functions.

Session and Individual. Treatment assignment will occur at the session level, with each experimental session randomly assigned to either the control condition or the professional impartiality reminder condition. Consequently, all participants within the same session will receive the same experimental condition.

Within each session, participants will be randomly assigned to one of two arbitrary colour groups (Blue or Green) and to one of two roles: Food Standards Inspector or Food Producer. In each round, each inspector will be randomly matched with four Food Producers comprising two ingroup and two outgroup producers. This group composition will remain fixed across rounds, while the specific inspector–producer matches will be randomised in each round.

Yes

Up to 44 experimental sessions, comprising 4 pilot sessions (2 control and 2 professional impartiality reminders) and 40 main experimental sessions. Main experimental sessions will be allocated equally between the two conditions. The final number will be determined based on a formal power calculation following the pilot.

Each experimental session will comprise 20 participants. At most 880 participants across including the pilot (176 Inspectors and 704 Food Producers). The final number will be determined based on a formal power calculation following the pilot.

Equally between the two conditions. The final number will be determined based on a formal power calculation following the pilot.