Do you remember the last time you were laughing and simply could not stop? Perhaps it was a situation when you should not have been laughing at all.

This happened to one of us while accompanying a friend to a family court in the middle of an unpleasant divorce case. It led to a rapid dash to the bathroom while desperately trying (and failing) to regain control – not quite the kind of emotional support this friend was looking for!

Another classic example is the cricket commentators Brian Johnston and Jonathan Agnew who laughed so much as they described the day’s play in 1991 that they could not talk at all. But how and why does this happen?

In fact, although we typically associate laughter with amusement, most of it occurs for other, social reasons. For example, you are 30 times more likely to laugh if you are with someone else than if you are on your own. And you’ll laugh more if you know your companion and like them.

Most laughter occurs during conversations, when people may laugh through contagion – catching the laughter from someone else. Studies show that when we see or hear someone laughing, this can trigger laughter in us almost automatically, promoting social bonding.

We often laugh to demonstrate agreement and understanding, and to cement friendship – for example, over shared recollections. We also laugh to reduce stress.

These common conversational laughs happen roughly six times per ten minutes of conversation, on average. They’re short, lower in pitch, and tend to start and stop quickly.

These types of laughter, which we refer to as voluntary, are different from the helpless laughter that incapacitates us, and which we cannot prevent from happening. Helpless or involuntary laughs are longer and higher pitched, involving strange squeaks and whistles.

In our latest research, we have investigated whether these two different kinds of laughter might have their roots in entirely different brain systems.

Things get difficult

When attempting to understand the brain networks that underlie the production of laughter, things can get difficult quickly.

For a start, people move a lot when they laugh. This can cause problems for brain imaging techniques such as fMRI (functional magnetic resonance imaging). It can also be extremely difficult to get people to laugh naturally under laboratory conditions.

Another issue is that different regions of the brain all appear connected to laughter. One of us (Fausto) collaborates with the epilepsy surgery unit at Niguarda Hospital in Milan, where patients with drug-resistant epilepsy undergo electrical brain stimulation for clinical purposes. Electrical stimulation is highly precise and not affected by movement.

Normally, if you stimulate the motor system, the patient will move. If you stimulate the visual system, they may experience hallucinations. And if you stimulate the auditory system, they will hear sounds. But there are five or six areas of the brain where stimulation triggers loud laughter in the patient. So, why is this?

We recently reviewed all brain stimulation studies of people laughing, and how they felt when they laughed. These studies provide evidence that the areas of the brain where stimulation evokes laughter form two different laughter networks.

In one, encompassing the anterior cingulate cortex, the temporal pole and some subcortical regions, stimulation led to laughter accompanied by pleasant sensations and happy feelings – this is the more helpless, high-pitched laughter. When there was stimulation to the other network, which is in the brain’s motor and premotor regions, laughter led to speech impairments and was not associated with any emotional state.

Evolutionary differences

The areas constituting the first, more joyous laughter network mapped on to a network for vocalising that humans share with all other mammals. This is potentially also responsible for other spontaneous emotional vocalisations such as crying out.

Activation of this network during spontaneous laughter triggers a neurochemical cascade that taps into, among other things, the opioid system. This helps to explain the sense of pleasure and reward that comes from this joyous, uncontrollable laughter. The serotonin system that regulates our sensitivity to pain is also affected, which may explain why this laughter can temporarily dull physical pain.

From an evolutionary perspective, this network is older. It originates in the spontaneous emotional responses and rough-and-tumble play systems of animals, and is therefore largely unchanged between humans and other animals.

The other, voluntary laughs mapped on to a brain network linked to voluntary movements in humans, such as speaking aloud. These have a primary role in strategic communication and social negotiation, so may explain the particular use of laughter in conversation as a sort of spoken punctuation.

This neural system is found mainly in humans, and is associated with complex vocal acts such as speaking, singing and beatboxing.

A 2022 study looking at the shapes our vocal tracts make when we laugh in this conversational way found they resemble the shapes we make when we speak. In contrast, the shapes of our vocal tract when we laugh helplessly look very unlike speech, and their motor control is simpler, consistent with their ancient origins.

This research shows that voluntary laughter requires more complex and refined motor control than spontaneous laughter, occupying a middle ground between spontaneous laughter and spoken language – not only functionally but anatomically as well.

If a person has a stroke that damages this voluntary network, they can develop severe problems with speech while still being able to laugh, cry and swear. We would argue that this is because the older network remains intact.

The science of laughter may seem like a rather frivolous subject – and neuroscientists have certainly devoted more effort to studying negative emotions such as fear, anxiety, anger and disgust.

However, research on human laughter is turning out to be something of a Rosetta Stone for understanding a surprising range of phenomena – including the origins of the social brain in mammals, the mechanisms of bonding and empathy, pain modulation, language in conversation, and emotional contagion.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

Think back to your time at school. Were you hard-working, popular, anxious? And what exam grades did you get? Now, imagine someone pulls out your school reports from that time. How closely would they match the results you just brought to mind?

If your recollections match exactly, you might congratulate yourself on having an excellent memory. But as a psychologist who has spent years researching what people remember – and misremember – my work often challenges the idea that the “best” memory is always the most accurate one.

In fact, some of the distortions commonly regarded as memory failures may be signs of a healthy and adaptive memory system. In many aspects of life, research suggests people misremember their past in predictable, self-protective ways, reshaping experiences to support their current, positive sense of self.

For example, a 1996 US study investigated how former pupils recalled 3,220 high-school grades. The study found they accurately remembered A grades 89% of the time, but D grades only 29%. Most of the errors saw grades misremembered as higher, suggesting many people carried with them an illusion of better academic performance.

Similarly, participants in a 2006 study underwent cholesterol screening, then were followed up months later to see how accurately they remembered the results. Most recalled having lower-than-reality cholesterol, especially those with the highest readings.

Positive memory biases such as these generally become more common as we get older. This is theorised to contribute to the well-documented positive relationship between age and wellbeing. And yet this kind of memory distortion is often regarded as a failure.

In law courts, hospitals and other high-stakes settings, of course, such errors can have serious consequences. For example, inaccurate eyewitness testimony is the leading contributor to wrongful convictions overturned by the Innocence Project.

But in everyday life, memory’s flexibility – and fallibility – are central to how it helps us survive and thrive. Memory is not a recording device. It is selective, reconstructive and shaped by what matters to us now.

So, what if today’s “total recall” technology is creating a memory system we do not need or benefit from?

The benefits of on imperfect memory

According to the late British psychologist Martin Conway’s self-memory system, autobiographical memory is not simply a storehouse of past events. It is a system that maintains a sense of self that is coherent, stable and generally positive.

Thus, when knowledge or feelings change over time, people often reconstruct memories to be more consistent with their present selves.

Psychologist Linda Levine and colleagues found this in a 2010 study of people’s memories of their reactions to the O.J. Simpson trial. As opinions about the killing changed over time, people tended to remember their original reactions as being closer to their current beliefs than they really were.

Many long-term relationships benefit from partners having imperfect, evolving memories. In a 20-year longitudinal study, satisfied spouses often remembered the earlier stages of their marriage as less happy than they had reported at the time, creating an illusion of improvement that predicted future relationship satisfaction. Certainly, long-term love would be difficult if couples retained every slight and badly phrased sentence in perfect detail.

Depression offers a revealing contrast. Compared with non-depressed individuals, people with depression often show less of the positive bias that characterises everyday remembering.

A memory system that is less inclined to soften failures, reinterpret setbacks or highlight positive experiences may be more faithful to the past. But it can also make it harder to maintain wellbeing and hope for the future.

A form of memory we may not want

This is why modern technology raises difficult questions. Much of our digital world is built on the assumption that more memory is better memory. Phones preserve thousands of images. Fitness watches record steps, sleep, heart rate and calories.

The arrival of AI assistants may further accelerate this shift, as systems that can instantly search, summarise and re-present years of messages and photographs influence how we remember.

There is some evidence that more remembering is not always better. People with the very rare condition of highly superior autobiographical memory can recall extraordinary detail from decades of their lives. However, many describe the experience as exhausting, with memories resurfacing vividly and involuntarily – making it much harder to move on from negative life events.

We are beginning to see examples of how technology-supported remembering can produce similar consequences, particularly in the context of grief, where platforms unexpectedly resurface photographs, birthdays or posts from people who have died.

AI systems can create intimate forms of digital remembering. Imagine asking an AI assistant what your relationship was like three years ago and receiving a summary generated from thousands of messages, photographs and calendar entries.

Humans have always used tools to remember, from diaries and monuments to photographs, songs and stories. The issue with today’s digital tools is that they are designed around a narrow philosophy of memory: preserve everything, quantify everything, resurface everything. But human memory did not evolve to preserve everything, or remember everything exactly as it happened.

This is not to say that technology should distort or rewrite the past. Most of us would not download a health app that invents flattering data for emotional convenience. But I believe we all need to give more consideration to the so-called imperfections of human memory – its selectivity, malleability, and capacity to soften, reorganise and reinterpret the past.

For centuries, people have designed technologies to compensate for memory’s weaknesses. We may now be building technologies that remove some of its strengths.

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Gillian Murphy's research is currently funded by the European Research Council, Lero (the Irish Centre for Software Research) and Rinn AI. Gillian is co-author of Memory Lane: The Perfectly Imperfect Ways We Remember (Princeton University Press, 2025).