Religiosity is very loosely defined, but is generally taken to mean "the tendency towards religious beliefs".

Over 80% of the global population consider themselves religious, with even more identifying as spiritual, __but the neural substrates of spirituality and religiosity remain unresolved."

[ Source link below ]

Throughout history, theologians - and more recently psychologists - have attempted to understand variations in the percentages of people who are 'believers'.

Although the reasons for the prevalence for human religiosity remain very obscure, most scholars lean towards the view that cultural forces (traditions etc.) are the main driving factors.

Other researchers suggest that tendencies towards religiosity and spirituality could be mapped to specific brain 'circuits'. In other words, suggesting it may be in some way 'hard wired'. But precise details of such circuits remain unknown.

A 2021 study from the Center for Brain Circuit Therapeutics at Brigham and Women’s Hospital, Boston, US, examined the self-reported 'religiosity' of people who had had suffered brain injuries during the Vietnam war. Using as a database the Vietnam Head Injury Study (VHIS) (ref,)

The research team found that spirituality and religiosity map to a common brain circuit centered on the PeriAqueductal Gray (PAG) - a brainstem region previously implicated in fear conditioning, pain modulation, and altruistic behavior.

In conclusion, our study demonstrates that lesions associated with spirituality and religiosity map to a human brain circuit defined by connectivity to the PAG. This brain circuit aligns with lesion locations from previous case reports of hyperreligiosity and with lesion locations previously associated with strongly held fixed beliefs and feelings of control by an external agent."

See : A Neural Circuit for Spirituality and Religiosity Derived From Patients With Brain Lesions, ^{[ paywalled ]} Biological Psychiatry, Volume 91, Issue 4, pp 380-388

Note that the study group was relatively small (n = 105), and the findings do not account for the very large variations in self-reported religiosity worldwide. (ref.)

Thus the relative importance of 'Nature' and 'Nurture' for religiosity remain unclear.