Disgust, Fear, or Sadness: Your Eyes Reveal What You Feel
- Apr 20
- 4 min read
Your eyes may reveal more than you imagine. A new study shows that the pupil doesn't just react to light; it changes shape depending on the emotion you feel. Disgust and sadness cause pupils to dilate more, fear appears later… and anger can even have the opposite effect. This means your eyes may be "giving away" exactly what you're feeling, even before you realize it.
Emotions not only affect what we feel inside, but also cause physical changes in the body. One of these changes occurs in the eyes, more specifically in the pupils, which can dilate or contract depending on what we are feeling.
For a long time, scientists have known that intense emotions, both positive and negative, can increase pupil size. However, it was still unclear whether different specific emotions, such as fear, sadness, or disgust, provoke distinct patterns in this response. This study sought to answer precisely that question, exploring how specific negative emotions influence pupil size.
The pupil is controlled by an automatic bodily system that regulates involuntary functions, such as heartbeat and breathing. When this system is activated, especially in emotional situations, it can cause the pupil to increase in size. This dilation depends not only on ambient light but also on emotional activation.
In other words, even under conditions of constant lighting, our pupils can expand when we feel something intense. Previous studies have shown that negative emotions tend to cause greater dilation than positive emotions, but these studies generally only analyzed emotions in general, without distinguishing between specific types.
Much of the previous research used stimuli previously classified by the scientists themselves as "positive" or "negative." This ignores an important aspect: each person can react differently to the same stimulus. An image considered sad by one researcher may not provoke the same emotion in all participants.
Furthermore, studies rarely gave importance to what the participants themselves said they were feeling. This created a significant gap in understanding how real, individually experienced emotions relate to changes in the body.
To overcome these limitations, the researchers developed an experiment more focused on individual experience. About two hundred people participated in the study. They were exposed to different emotional stimuli, including images and sounds designed to provoke varied reactions, such as joy, fear, sadness, anger, and disgust.
After each stimulus, participants reported what they were feeling and the intensity of those emotions. Meanwhile, specialized equipment continuously recorded pupil size, allowing them to observe how pupils changed over time in response to each stimulus.
The results showed that different negative emotions do indeed affect the pupil in distinct ways. Disgust and sadness were the emotions that most increased pupil size, with disgust showing the strongest and most consistent effect. This dilation began a few seconds after the start of the stimulus and remained throughout its presentation.
Happiness also caused pupil dilation, but more mildly. Fear caused a delayed dilation, appearing more towards the end of the experiment. Interestingly, anger had a different effect: instead of increasing pupil size, it was associated with a decrease in pupil size in some cases.
These findings show that the pupil may be a more detailed indicator of emotions than previously thought. Instead of simply reflecting overall emotional intensity, it can also differentiate specific types of emotions. This opens up new possibilities for the study of human emotions, especially in contexts where people cannot or do not want to verbally express what they are feeling.
In the future, this approach could be useful in areas such as clinical psychology, neuroscience, and even technology, helping to better understand individual emotional experiences.
READ MORE:
Differences in pupil size during self-reported experiences of disgust, sadness, fear, anger, and happiness
Kate McCulloch, Edwin S. Dalmaijer, Gerulf Rieger, and Rick O’Gorman
Biological Psychology. Volume 198, May 2025, 109044
Abstract:
Previous research has found pupil dilation associated with stimuli pre-assigned as positive and negative in their emotional valence; however, it is not yet clear how self-rated experiences of specific emotions may correlate with differences in pupil size. Using a novel methodology across two studies, 200 participants were presented with emotionally engaging images and sounds and then rated the extent to which they felt happy, sad, angry, fearful, and disgusted in response to these. Data were analyzed using linear mixed effects models to examine whether the participant’s own emotion ratings predict pupil size. In 2 studies using standardized images and sounds, and varied 30-s audio clips, in trials with higher self-reported disgust and sadness there was a consistent relationship with pupil dilation. Disgust was most often the strongest predictor of pupil dilation. This effect emerged ∼2 s after stimulus onset and remained present throughout stimulus presentation. Happiness had a weaker effect on pupil dilation and fear was associated with a late pupillary response. Anger was associated with pupil constriction, but only in Study 2. The present approach finds the most consistent relationship between pupil dilation and self-rated disgust and sadness, compared to other negative emotions. The findings thus suggest that measures of pupil size warrant further investigation as a potential indicative psychophysiological correlate of self-reported emotions, with implications for distinguishing negative emotions, such as disgust from anger.
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