3
The number of types of tears the human body produces: basal tears, which keep our eyes lubricated; reflex tears, which we cry in response to physical triggers, like dust or onions; and emotional tears.
15 millimeters
The amount of paper that a healthy person's tears will wet, when the paper is placed into the lower eyelid for 5 minutes, in a test called the "Schirmer test" to diagnose dry eyes. Tear production generally declines with age, the test has found.
30 to 64
The average number of times a year that women cry emotional tears, as compared with 5 to 17 times per year for men, according to a study of self-reports from more than 7,000 people in 37 countries. The study authors suggest that the difference between men and women may be more pronounced in countries where the culture permits greater freedom of emotional expression.1
2.25 hours
The mean amount of time 6-week-old babies cry each day, according to a meta-analysis of studies involving almost 8,700 infants worldwide. Crying begins to drop off after that, to 68 minutes per day, on average, by 12 weeks. Babies in the United Kingdom, Canada and Italy cried the most, while babies in Denmark, Germany and Japan cried least.2
1Country and Crying: Prevalences and Gender Differences
van Hemert, D. A., van de Vijver, F. J. R., & Vingerhoets, A. J. J. M. Cross-Cultural Research, 2011
2Systematic Review and Meta-Analysis: Fussing and Crying Durations and Prevalence of Colic in Infants
Wolke, D., Bilgin, A., & Samara, M. The Journal of Pediatrics, 2017