# Gender “in the wild”: toward a person-specific behavioral neuroendocrinology

## TL;DR

This paper argues for studying individual differences in sex and gender effects on behavior using personalized data from daily life observations.

## Contribution

The novelty lies in using intensive longitudinal data and idiographic analyses to study the interplay of sex-related neuroendocrinology and gender-related self-concepts in unique individuals.

## Key findings

- Mean-based analyses may obscure individual differences in sex and gender effects on behavior.
- Idiographic approaches reveal unique relations between neuroendocrinology and self-concepts in daily life.
- Intensive longitudinal data with up to 100 daily assessments can capture individualized patterns.

## Abstract

Sex- and gender-related contributions to behavior “in the wild”, as observed in humans in the natural context of their daily lives, can vary strikingly across individuals and be highly enmeshed – so much so that it is impossible to determine whether an average difference between women and men, for instance, reflects biological or sociocultural factors, respectively. Indeed, empirical insights may not just be limited, but may even be distorted, if study designs and data analyses continue to place unique people in ill-assumed homogenous groups for mean-based calculations. Findings may ultimately generalize to no one. An idiographic, or personalized, approach, however, reveals the intricate ways in which sex-related characteristics, such as gonadal hormones, and gender-related experiences combine to matter for behavior. This approach often requires novel data, that is, many repeated observations from the same people on the same variables, and time series analyses. The goal of this article is to briefly review perspectives on sex and gender in research, and then to illustrate how sex- and gender-related factors can be studied together in unique individuals using an idiographic approach. Specifically, person-specific analyses of data from select participants in three different intensive longitudinal studies with 75 or 100 assessment days will showcase unique relations between sex-related neuroendocrinology (i.e., menopause, oral contraceptive use, and puberty) and gender-related self-concepts (i.e., perceptions of masculinity and femininity), or demonstrate links with cognition or mental health. These illustrations will highlight the importance of leveraging methodological innovation to study the individualization of sex and gender, and the necessity of decreasing reliance on sex- and gender-linked assumptions of homogeneity in human neuroendocrine research.

The interplay of sex- and gender-related factors “in the wild”, or as they naturally unfold in the day-to-day lives of unique individuals, often remains undetected in mean-based analyses that focus on static between-group differences.

This article illustrates the necessity of taking an idiographic approach (focusing on within-person variation), which requires intensive longitudinal data (with many repeated observations) and person-specific data analyses, to the integrated study of human neuroendocrinology and gender-related self-concepts.

Individuals from three intensive longitudinal studies consisting of up to 100 daily observations were highlighted, leveraging analyses that treat each individual as their own case study of N = 1.

Variation in the gender-related aspect of self-perceived masculinity and/or femininity was considered in all cases, and the sex-related aspects of menopause, the menstrual cycle and hormonal contraceptive use, and puberty were each considered in a subset of cases.