While the actual pigment in the iris does not change color with mood, various factors can make eyes appear to shift in shade. The perception of eye color is influenced by more than just the inherent pigmentation. This phenomenon often leads to the common misconception that emotions directly alter the color of one’s eyes.
What Determines Eye Color?
Eye color is primarily determined by the amount and type of melanin present in the iris, a pigment also responsible for skin and hair color. High concentrations of melanin, specifically eumelanin, result in brown eyes, which are the most common eye color globally. Eyes with less melanin, such as blue eyes, do not contain blue pigment but appear blue due to Rayleigh scattering, a phenomenon where light scatters in the iris’s stroma, reflecting shorter blue wavelengths. Green eyes have moderate amounts of both eumelanin and pheomelanin (a yellowish pigment), combined with light scattering. These melanin levels and iris structure are stable after early childhood and do not change with emotional states.
Why Eyes Might Appear to Change Color
Many factors contribute to the perceived shifts in eye color. Lighting conditions significantly influence how eye color is seen; natural sunlight, artificial light, and the intensity or angle of light can alter the reflection and absorption, leading to a different perceived hue. For instance, eyes might seem brighter or darker depending on the surrounding illumination.
The size of the pupil plays a role; when pupils dilate or constrict, they change the amount of the iris that is visible and alter the contrast, which can make the eye appear lighter or darker. Pupil size is influenced by light levels and can also expand or shrink in response to emotional arousal. Additionally, the colors of clothing, makeup, or the immediate environment can create optical illusions through contrast, making the eyes seem like a different shade. Reflections on the eye’s surface can also momentarily alter its perceived color. Furthermore, redness in the white of the eye (sclera) from irritation or crying can make the iris appear to have a different hue by comparison.
How Mood Does Affect Your Eyes
Emotions can induce several visible physiological changes in the eyes. The autonomic nervous system responds to emotions like excitement, fear, or anger by causing pupils to dilate or constrict with relaxation. This sympathetic activation increases pupil diameter.
Emotional responses also trigger tearing and crying. These emotional tears differ in composition from reflex tears and can contain stress hormones. Strong emotions or crying can also cause blood vessels in the sclera to dilate, leading to bloodshot eyes. Finally, emotions can affect the muscles around the eyes, resulting in physical manifestations such as squinting, widening of the eyes, or rapid eye movements due to muscle tension.