Abstract
Women were historically excluded from research participation partly due to the assumption that ovarian hormone fluctuations lead to variation, especially in emotion, that could not be experimentally controlled. Although challenged in principle and practice, relevant empirical data are limited by single measurement occasions. The current paper fills this knowledge gap using data from a 75-day intensive longitudinal study. Three indices of daily affective variability—volatility, emotional inertia, and cyclicity—were evaluated using Bayesian inferential methods in 142 men, naturally cycling women, and women using three different oral contraceptive formulations (that “stabilize” hormone fluctuations). Results provided more evidence for similarities between men and women—and between naturally cycling women and oral contraceptive users—than for differences. Even if differences exist, effects are likely small. Thus, there is little indication that ovarian hormones influence affective variability in women to a greater extent than the biopsychosocial factors that influence daily emotion in men.
Highlights
Women were historically excluded from research participation partly due to the assumption that ovarian hormone fluctuations lead to variation, especially in emotion, that could not be experimentally controlled
Of particular relevance is a meta-analysis on sex differences in physiological and trait variability that included over 300 studies and 6,000 data points in r ats[9]
Continuous measurement of locomotion and body temperature across 12 days revealed that males were more variable across a day, but that females had a four-day cyclic pattern that coincided with their estrous cycle
Summary
Women were historically excluded from research participation partly due to the assumption that ovarian hormone fluctuations lead to variation, especially in emotion, that could not be experimentally controlled. Female animals and humans were excluded from biomedical, neurological, and social research for decades because cyclic fluctuations in ovarian hormones were assumed to induce variability that would undermine statistical inferences or experimental manipulations[1,2]. Studies about intra-individual variability in rodents are not directly applicable to human biology (let alone behavior), they are important because there is scant evidence concerning sex differences in intra-individual variability of psychological traits in humans—even traits that fluctuate with time and are associated with ovarian hormones, such as emotion. It is related to personality, especially to neuroticism[11,14,15], and to internalizing psychopathology in comprehensive meta-analyses[16,17,18]
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