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Why do people have children at young ages? Investigating how population dynamics impact family planning decisions (RDF23/PSYC/ROTELLA)

   Faculty of Health and Life Sciences

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  Dr Amanda Rotella, Dr Jose Yong  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

Why do people have children at young ages? Young parents (16-25) face discrimination, hardship, and have fewer educational and employment opportunities, compared to older parents (Conn et al., 2018; Sheeran et al, 2021; Umberson, Crosnoe, & Reczek, 2010). This impacts their course of life, such that being a young parent is associated with lower educational achievement, fewer employment opportunities, and poorer health outcomes (Assini-Maytin & Green, 2015; Cox et al., 2008; Hoffmann & Vidal, 2017). These trends have implications for the NorthEast of England, which has the highest rate of teenage pregnancy in the country.

One surprising explanation is population density, where higher densities are associated with lower fertility rates and later age at first birth. Recent studies have also found that population density is related to many behaviours and outcomes, such that lower population densities are associated with fewer planning, shorter life expectancies, earlier age of marriage, earlier age at first birth, higher birth rates, lower educational attainment, and lower rates of preschool enrolment (Rotella et al., 2021; Sng et al., 2017).

The question is why – why would population density influence human psychology? Why do people living in high density environments wait to start families, while people living in low density environments do not?

A partial explanation is that there are different trade-offs in high- and low-density environments. In high density environments, it is harder to compete for resources (e.g., jobs, housing) compared to low density environments. Therefore, people invest more resources (time, energy, money) in themselves (e.g., getting a higher education) to succeed in dense environments. Yet, how or why density changes family planning decisions is still untested.

This project will bridge this gap, by investigating two questions:

  1. Do perceptions of population density alter perceived payoffs for family planning decisions? That is, do people in low-density environments perceive more benefits of having children earlier compared to people in high-density environments?
  2. Do perceptions of population density interact with inequality? In other words, do people perceive greater benefits of having children earlier in dense environments with high-inequality compared to low-inequality?

This project will use both immersive virtual reality experiments and secondary data analysis of real fertility decisions within the UK to advance our understanding of how density impacts family planning decisions.

This line of research will have broad impact. First, these insights are important to understand when and why there will be high teenage birth rates. This is of particularly importance for the North East, which has the highest rates of teenage pregnancy in England. Second, there’s been a worldwide decline in fertility rates (the demographic transition), which has received much political and media attention due to the implications for economies and pensions. The insights gained from this research will be used to address and understand both social issues.

This project will be supervised by Dr Amanda Rotella (amandarotella.ca), Dr Jose Yong (https://joseyong.com/), and Prof Thomas Pollet (https://tvpollet.github.io/). 

Academic Enquiries

This project is supervised by Dr Amanda Rotella, Dr Jose Yong, and Prof Thomas Pollet. For informal queries, please contact Amanda Rotella at [Email Address Removed]. For all other enquiries relating to eligibility or application process please use the email form below to contact Admissions. 

Funding Information

Home and International students (inc. EU) are welcome to apply. The studentship is available to Home and International (including EU) students and includes a full stipend at UKRI rates (for 2022/23 full-time study this is £17,668 per year) and full tuition fees. Studentships are also available for applicants who wish to study on a part-time basis over 5 years (0.6 FTE, stipend £10,600 per year and full tuition fees) in combination with work or personal responsibilities).  

Please also see further advice below of additional costs that may apply to international applicants.

Eligibility Requirements:

  • Academic excellence of the proposed student i.e. 2:1 (or equivalent GPA from non-UK universities [preference for 1st class honours]); or a Masters (preference for Merit or above); or APEL evidence of substantial practitioner achievement.
  • Appropriate IELTS score, if required.
  • Applicants cannot apply for this funding if they are already a PhD holder or if currently engaged in Doctoral study at Northumbria or elsewhere.

Please note: to be classed as a Home student, candidates must meet the following criteria:

  • Be a UK National (meeting residency requirements), or
  • have settled status, or
  • have pre-settled status (meeting residency requirements), or
  • have indefinite leave to remain or enter.

If a candidate does not meet the criteria above, they would be classed as an International student.  Applicants will need to be in the UK and fully enrolled before stipend payments can commence, and be aware of the following additional costs that may be incurred, as these are not covered by the studentship.

  • Immigration Health Surcharge https://www.gov.uk/healthcare-immigration-application
  • If you need to apply for a Student Visa to enter the UK, please refer to the information on https://www.gov.uk/student-visa. It is important that you read this information very carefully as it is your responsibility to ensure that you hold the correct funds required for your visa application otherwise your visa may be refused.
  • Check what COVID-19 tests you need to take and the quarantine rules for travel to England https://www.gov.uk/guidance/travel-to-england-from-another-country-during-coronavirus-covid-19
  • Costs associated with English Language requirements which may be required for students not having completed a first degree in English, will not be borne by the university. Please see individual adverts for further details of the English Language requirements for the university you are applying to.

How to Apply

For further details of how to apply, entry requirements and the application form, see


For applications to be considered for interview, please include a research proposal of approximately 1,000 words and the advert reference (e.g. RDF23/…).

Deadline for applications: 27 January 2023

Start date of course: 1 October 2023 tbc


• Rotella, A., Varnum, M. E., Sng, O., & Grossmann, I. (2021). Increasing population densities predict decreasing fertility rates over time: A 174-nation investigation. American Psychologist, 76(6), 933.
• Sng, O., Neuberg, S. L., Varnum, M. E., & Kenrick, D. T. (2017). The crowded life is a slow life: Population density and life history strategy. Journal of Personality and Social Psychology, 112(5), 736.
• Yong, J. C., Lim, A. J. Y., & Li, N. P. (forthcoming). When social status gets in the way of reproduction in modern settings: An evolutionary mismatch perspective. Culture and Evolution.

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