Every now and then I run across a neuroscientific study that makes me think in a new way, because it tries a fresh angle or studies something no one has studied before. A study from 2014 I just encountered accomplishes exactly that.

The study, published in Motivation and Emotion, by Verduyn & Lavrijsen, 2014, asked the apparently simple question, how long do emotions last? The answer is fascinating, and not at all simple. It’s not the case that negative emotions last and positive ones are fleeting, for example. An apparently random collection of positive and negative emotions come and go very quickly, whereas a similar set of both kinds of emotions last a good deal longer. Nor is it always the case that the importance of the event triggering the emotion determines how long it lasts.

Of course, trivial events that come and go by the score during the day won’t necessarily cause emotions to stick with you, and earth-shaking moments will probably last longer, emotionally speaking. But we can never be sure how an event will strike us.

One of my first summer jobs was working for my dad, a scientist, in his lab. I was sixteen. My job was to feed a culture of anaerobic amoebae he was using in his work. One day I accidentally introduced some oxygen into the mix, instantly killing the culture. It was not a catastrophe, but it did set him back a week or two, and Dad was annoyed. In his pique, he said, “Obviously you’re not cut out to be a scientist.”

He forgot the comment in a few weeks, probably when the new culture was established, but I have remembered it for half a century and the sting of it is at least in part why I never did become a scientist.

OK, my career choices aside, what does determine how long an emotion lasts? In a word, rumination. Saskia Lavrijsen, co-author of the study, says, rumination “is the central determinant of why some emotions last longer than others. Emotions associated with high levels of rumination will last longest.”

At the short end of the emotional race, we have disgust, shame, humiliation, fear, and compassion. Irritation is in a dead heat with compassion, which makes me a bit sad to learn. These emotions typically last a half-hour, give or take. On the long side, we have anxiety, hope, desperation, joy, hatred, and the winner by several lengths: sadness. Sadness is the outlier, lasting five days, or twice as long as the next closest entrant, hatred.

Of course, sadness is a marker for depression, and that’s a tough, quiet killer of human feeling, relationships, and happiness. So perhaps it’s not surprising — surprise being an emotion that itself only lasts about two hours.

Some emotions that naturally seem to pair together sit at opposite ends of the spectrum – our fear is brief, but anxiety lasts a long time – typically 24 hours. Shame goes quickly, but guilt stays with us, three and half hours compared to 30 minutes. Again, the key seems to be how much we are inclined to ruminate on the emotion and the incident that brought it up.

Brene Brown’s wonderful book, The Atlas of the Heart, helps make us aware of the incredible richness and nuance of human emotion. This study complements her work nicely, and shows us, in a very concrete way, how different emotions have much different weight in terms of their duration. It’s an important reminder that we have a responsibility to our fellow humans, whether we are colleagues, teachers, family, or friends, to understand what we are putting them through when we invoke an emotion in them. We should be very careful about the longer-lasting emotions especially, given that we may affect someone’s life for almost a week by introducing, in particular, the emotion of sadness. The Buddhists teach that the mind is like the sky, and emotions are like clouds that pass through the sky. One should just watch those clouds float by, rather than attaching oneself to them. This study suggests that that work may be considerably harder or easier depending on the emotion in question.