Dear Dr Ash,

I love a good discussion about politics but one of my closest friends is always pushing the envelope. He just won’t let things drop and when I try to change topic if things are getting overheated, he rapidly steers it back. Worse still, he will almost always spend the next two weeks sending me articles and opinions from X in an effort to make me see the supposed error of my ways. This has become worse since he took up some cranky opinions over the Covid years (you know the sort of thing, the vaccinations were more harmful than useful, it was definitely a lab leak) and has even been arguing he wishes there was a Robert F Kennedy in UK politics. I’m a pretty tolerant person, but this is pushing me over the edge.

On Edge,
Margate

When we debate we must remember that our mechanisms of reasoning might differ

Dear On Edge,

I imagine that ancient Athens was a hot place. Its citizens would have stood under a scorching Grecian sun, drenched in sweat, undoubtedly vexed and irritating the hell out of each other. And yet these Athenians somehow felt that heated arguments between ordinary people could lead to an effective form of government. So here we are, millennia later, still spending much of our time shouting over each other. Democracy would be lovely if it weren’t for the demos.

But we’ve learned a few things about the neuroscience of decision-making since the days of Pericles, and perhaps some of these insights can shed light onto your dilemma. First, it is clear that reason is not nearly as reasonable as the Athenians believed. Every function of the brain is dependent on fluctuating hormones, blood sugar and levels of fatigue. We reason differently when we are in groups than when we are alone, differently in the summer than in the winter, and differently when we are hungry, tired or sad. We are biological creatures and we function as such. It’s almost never the case that evidence and debate radically alters our perspectives – we change our ideas through our relationships. If your friend really wants to get you to change your mind, they should focus more on making you feel comfortable and engaged than on bombarding you with evidence – that also has the upside of being far more fun.

Secondly, the ancient Athenians won’t have read Thomas Bayes’s Essay towards Solving a Problem in the Doctrine of Chances, not because it is ponderous and boring, but because it was published in 1763. Bayes articulated a view on probability and statistics that has come to underlie what neuroscientists believe is the fundamental mechanism the brain uses to process information. The theorem named after him is a mathematical way of dealing with uncertain knowledge; it allows you to combine the probability that a theory is true with the probability that new evidence is true to give you an updated probability for that theory. So if I think that my dog ate my sandwich while I was out of the room, I can combine the new evidence (the clear absence of a sandwich) with the prior probability of the theory being true (close to zero since I don’t have a dog) to conclude that although my theory is stronger than it was, it’s still nonsense.

In this way, the theorem describes how the brain updates information based on context. This is crucial because our senses are limited and unreliable. We see in fleeting glimpses, we hear in a cacophony, we feel through skin thick enough to protect us but thin enough to enable touch. Without prior expectations, the brain would be unable to perceive anything other than a noisy, blurry, deeply confusing world – and indeed that’s how the world appears to babies until they start to accumulate some Bayesian priors.

Since prior probabilities matter so much to brain function, when we debate we must remember that it’s not just our opinions but our mechanisms of reasoning that might differ. We are starting from different positions and updating our uncertain beliefs about the world with new evidence of uncertain reliability. This is a deeply personal and idiosyncratic process, and the only way to have a productive debate is to be respectful of these different starting positions. Maybe part of the frustration you’re feeling with your friend is because he is providing you with lots of answers but asking very few questions. It’s interesting to wonder why we think what we think, and it’s great fun to spend time with a friend exploring ideas. It’s boring (and pointless) to just be told. You may be able to convince your friend to be a more entertaining conversationalist by gently teasing him about his tendency to get the bit between his teeth. But I promise you won’t change his mind by repeatedly sending him a copy of this letter.

Best wishes,
Dr Ash

Dear Dr Ash,

This may sound silly but I’m worried that my 21-year-old daughter is not having enough fun. She’s constantly anxious about her coursework (she’s in her second year at university and always gets good grades), her friends’ mental health and climate change – to the point she rarely seems to actually enjoy herself. When I was young in the late 1980s and early 1990s I was having a whale of a time. I went to all-night raves with my mates, travelled, drank, smoked and took recreational drugs such as ecstasy. Yes, I worried about politics too, but I took advantage of being young, free and unfettered to live life to the full – because you’re never as free again as you are at that stage of life. I’m worried my daughter is wasting that special moment of freedom.

Fun-lover
Northampton

The prevalence of diagnosed mental health disorders in the young is increasing

Dear Fun-lover,

I have just read your letter after a walk through Hyde Park on what must be one of the nicest mornings we’re likely to see in England this year. Blue skies, endlessly luxurious sunshine and a soft breeze that seems scented by the sea. I was reminded of a scene in Marquez’s Love in the Time of Cholera in which the erudite Dr Urbino is strolling down a Parisian boulevard in the autumn, arm-in-arm with a lover, drinking in “the woody odour of chestnuts on the braziers, the languid accordions, the insatiable lovers kissing on the open terraces” and nevertheless yearning for the halcyon days of his youth in the Caribbean. Urbino cannot fully enjoy the present for his love of the past, because, as Marquez tells us, “he was still too young to know that the heart’s memory eliminates the bad and magnifies the good”.

This transformation of memory across time is both personal and generational. We imagine that our childhoods were more pleasant, more exuberant, more authentic than those of our children, just as our parents imagined the same about us. These memories, which cognitive scientists refer to as “autobiographical”, work differently than memories for facts. Every time the brain recalls an autobiographical memory, it saturates it with emotion. The limbic system then actively reshapes these memories based on their emotional relevance. In the absence of trauma, when you recall a distant memory your mesolimbic system will release a flood of dopamine, creating a pleasurable feeling in the act of recall itself but also reinforcing the positive parts and weakening the negative parts of that memory. Your brain simply rewrites the script. You remember the delightful picnic in the park with your family but not the ants, the fabulous evening at a nightclub with friends but not the heaving crowds. The biological mechanisms that underpin memory will inexorably, over time, create the feeling of nostalgia.

But while some of the distance you are perceiving between your own happy youth and what you see your daughter going through is surely due to nostalgia, you are not alone in worrying about anxiety among the young. The prevalence of diagnosed mental health disorders in the young is increasing and the language of anxiety is nearly ubiquitous. Faced with the onslaught of smartphones, climate change, a dismal economic future and the rise of the far Right around the world, young people have plenty of reasons to be anxious. However, research in social neuroscience suggests that these big world events don’t affect the young as much as we might think. Instead, the main sources of anxiety in their age group probably are, and have always been, social: who is popular, who is dating whom, what clothes you should wear and what you used to wear but wouldn’t be caught dead in now – all layered onto the fundamental questions of creating an identity, defining a life trajectory, making a place for yourself in the world. You and I may look back and forget that we once worried about these questions, but if you manage to find an old journal or letters you wrote to friends I think you’ll be surprised. The differences between your experience and your daughter’s may not be as great as they seem. And given the brain mechanisms involved, I can assure you that as long as your daughter feels safe and loved, in time the memories of her youth will be as glittering to her as yours are to you.