Why do humans cry

Overview

Crying is a complex human behavior with evolutionary roots dating back millions of years. While many animals produce tears for eye lubrication and protection, emotional crying appears to be uniquely human, with evidence suggesting it evolved as a social communication tool. Historical records from ancient civilizations show crying was recognized as significant - Aristotle wrote about crying in his 4th century BCE work "Poetics," describing it as cathartic. In the 17th century, René Descartes identified three types of tears in his treatise "The Passions of the Soul." Modern scientific study of crying began in earnest in the 1970s, with researchers like William Frey at the University of Minnesota conducting groundbreaking studies in the 1980s that analyzed tear composition. Today, crying is studied across multiple disciplines including psychology, neuroscience, and biochemistry, with researchers examining everything from cultural differences in crying behavior to the neurological pathways involved in tear production.

How It Works

The physiological mechanism of crying involves the lacrimal system, which includes the lacrimal glands above each eye that produce tears, and drainage pathways through the nasolacrimal ducts. When triggered, the autonomic nervous system activates tear production through parasympathetic stimulation. For emotional crying, the limbic system (particularly the hypothalamus and amygdala) sends signals to the lacrimal glands via the facial nerve. Three distinct types of tears exist: basal tears continuously lubricate the eyes (approximately 1.2 milliliters daily), reflex tears respond to irritants like onions or wind, and emotional tears result from psychological stimuli. Biochemically, emotional tears contain higher concentrations of proteins, manganese, and stress hormones like adrenocorticotropic hormone (ACTH) and prolactin compared to reflex tears. The actual crying process involves increased tear production, changes in breathing patterns, and often vocalizations, with the average crying episode lasting about 6 minutes according to research.

Why It Matters

Crying serves important psychological and social functions that impact human wellbeing and relationships. Psychologically, crying provides emotional catharsis by releasing built-up stress hormones and triggering endorphin production, which explains why people often report feeling better after crying. Socially, tears serve as powerful non-verbal communication that elicits empathy and support from others, strengthening social bonds. In healthcare, understanding crying patterns helps diagnose and treat conditions like depression, where crying frequency often changes significantly. Culturally, attitudes toward crying vary widely - while some societies view public crying as weakness, others see it as healthy emotional expression. Research continues to explore crying's therapeutic benefits, with studies showing controlled crying interventions can help manage chronic pain and improve emotional regulation in clinical settings.