Frequently Asked Questions

Who can take part?

To participate in these studies, you must meet the following eligibility criteria:

  • Male

  • Right-handed

  • Caucasian

  • Between 18 and 50 years of age

  • Grew up in the UK or other European country

  • Body Mass Index 18.5 to 30 (if you are unsure of your BMI, you can check it here)

Unfortunately, we cannot include anyone with the following:

  • Current diagnosis of neurological or psychiatric condition

  • Use of antibiotics within the last 3 months

  • Current or history of regular smoking

  • Regular consumption of >14 units of alcohol per week

  • Current use of psychotropic drugs for medicinal or recreational purposes

  • Use of probiotic/prebiotic supplements

  • History or current diagnosis of gut microbiota related conditions such as inflammatory bowel disease or irritable bowel syndrome

If you would like to take part in the study, please follow this link to see if you are eligible.

Why are there such eligibility criteria?

The reason for certain participant exclusion criteria (e.g. gender, ethnicity) is due to the fact that these are known sources of significant variation. Since we are interested in the impact of gut microbiota on brain and behaviour, incorporating large sources of variation within our sample is going to limit the inferences we can draw. This enables us to gain a clearer understanding of our results, as this is one of the first studies of its kind. We hope that we will be able to extend our study to different groups in the future, subject to availability of research funding.

How long will my study visit take?

Screening Visit

To take part in either study, you will first be asked to attend the University of Reading to complete a screening visit. Prior to your arrival, you will be asked to complete a set of online questionnaires (approximately 30 minutes in total). At your screening visit, one of our researchers will explain the study to you in further detail and ask you to complete a consent form if you agree to participate. You will be provided with a sample kit, which you will be asked to bring with you on the day of the study. The screening visit should not take longer than 30 minutes.

We are currently also offering online screening visits using Microsoft Teams if you are unable to attend in person. In this case, we would ask you to stop by the University of Reading at another time to collect your sample containers prior to your first study appointment. We will be on campus Monday-Friday between 9am and 5pm should you choose this option. Alternatively, if you live outside of the local area, we can post the sample kit out to you.

Study 1

If you take part in Study 1, you will be asked to attend the University of Reading on one occasion. You will also be asked to collect a urine and faecal sample at home on the day of the study and bring this along with you your appointment. Once you are at the university, you will be asked to provide a blood sample and complete some body composition measures. You will then have an MRI scan and complete a small number of tasks on the computer. Your whole study visit should not take more than 3 hours, but we ask you to allow for up to 4 hours of your time.

Study 2

If you take part in Study 2, you will be asked to complete the same tasks as for study 1 another 3 times (i.e., you will need to come to the University of Reading for four study visits in total). You will also be asked to take a probiotic supplement every day for 4 weeks and a placebo supplement every day for another 4 weeks (you will not know which is which). The 4 study visits will be spaced out over a 4 month period (16 weeks).

Will I be paid for my time?

Yes. Participants will receive £50 for taking part in Study 1 or £50 per study visit in Study 2 (£200). We will also offer a £50 bonus to participants who complete all 4 study visits in Study 2.

We will also cover travel expenses for all screening and study visits.

Please note that volunteers will be remunerated for their participation and reimbursed for any travel costs at the end of their involvement with the study.

How do I get to my study appointment?

The study will take place at the University of Reading Whiteknights Campus. You will be greeted by one of the researchers at the entrance to the Hugh Sinclair Unit (Harry Nursten Building) and then move to the School of Psychology and Clinical Language Sciences (Harry Pitt Building).


If you are driving, we can provide you with a parking permit to park at the Hugh Sinclair Unit or at the School of Psychology and Clinical Language Sciences. For the Hugh Sinclair Unit, please use Car Park 10, and for the School of Psychology and Clinical Language Sciences, please use Car Park 25. There are parking spaces reserved for study volunteers at both car parks.

Public transport

For those who prefer public transport, the University is well connected by both trains and buses. If you are getting the train, the closest station is Earley - this is a 15 min walk from the School of Psychology and Clinical Language Sciences.

If you are getting the bus, the number 17, 19a and 21 buses all stop at Whiteknights campus and will get you within a short walk to the School of Psychology and Clinical Language Sciences or the Hugh Sinclar Unit.

Some useful links

You may use the following links to find the exact entrances at which you will be met by us:

What happens if I feel unwell during the study?

Please let one of the researchers know if you are feeling unwell during or leading up to your study visit. If you are experiencing any digestion-related illness, this could affect your microbiome and is important for us to know.

If you are taking part in Study 2 and are feeling unwell while taking either the placebo or probiotic supplement, please report this to the researchers at - we will be able to advise you whether or not you should continue with the study.

If you are experiencing symptoms of Covid-19 or have been in contact with someone who has Covid-19, please let one of the researchers know immediately. If you are due to attend a study visit, we may need to postpone.

What happens if I don't want to take part anymore?

Taking part in this study is completely voluntary; you may withdraw at any time without having to give any reason. Please feel free to ask the researchers any questions that you may have about this study at any point. Alternatively, you can email us with your questions at

I have a question that isn't on this page

If you have any other questions or would just like to learn more about the study, feel free to contact us at