Corn, before we get going, I have to say this one's been sitting in my head since the prompt came in, because Daniel's back on the sensory beat, and it's my favourite version of him.
The man is nothing if not consistent.
We've done the sound side. Building noise, the litmus test, all of it. Now he's back with smells.
Right. So for anyone who missed the sound episodes — actually no, we're not doing the recap. The short version is Daniel has ADHD, sound pulls his focus, and his proof that it isn't imagination is what he calls his litmus test: uncharacteristic errors. Losing the train of thought. Getting punctuation wrong in a sentence he'd normally nail. And now he's noticed the exact same error signature shows up when Hannah puts the coffee on while he's working at the table next to the kitchen. Cooking does it too. He's very clear it's not dislike — if he weren't working, the coffee smell wouldn't bother him at all. He wants a name for it, he wants to know whether the smell-noise parallel is real, and he's split on the fix: adapt the environment — no extractor fan, smallish apartment — or work on himself.
And he's honest about which one he's drawn to. He likes the idea of fixing himself better.
He does. Let's start with the naming question, because the vocabulary here is contested.
The framework he's reaching for exists. It just doesn't have the status he might expect.
I was going to say, there's a word he didn't use. The one everybody reaches for.
Sensory processing disorder. SPD. And the maddening thing is it should fit — it's been around since Jean Ayres defined it in the seventies, and it explicitly covers smell and taste alongside hearing, vision, touch, the vestibular and proprioceptive stuff, all eight channels or however you're counting that week. Daniel's issue sits inside the framework on paper.
"On paper" is carrying a lot of weight there.
Because it's not in the DSM. The American Academy of Pediatrics came out in twenty twelve and told pediatricians not to use it as a stand-alone diagnosis — there's a live argument about whether it's its own disorder or a cluster of symptoms that ride along with better-established ones. He won't get those three letters on a chart in most places.
So what does he get on a chart?
The more precise term is sensory over-responsivity, SOR, which is a subtype of sensory modulation disorder. Miller's group defined that in two thousand seven as difficulty responding in a graded and adaptive manner to the degree, nature, or intensity of sensory information. And you notice immediately that's about responsivity. Not attentional capture. The clinical vocabulary describes a dial turned up too high. What Daniel's describing is a hand reaching in and turning the page.
That gap is the whole episode, isn't it.
Part of it, anyway.
Well — his question was how this fits with ADHD sensory stuff. And that's where I remember it getting messy, because didn't we do an episode on this? ADHD and sensory processing?
We did, and I'll be honest, going back into it, it's messier than I remembered. The two best studies on whether smell is even part of the adult ADHD sensory picture flat-out disagree. Twenty twenty, forty-five adults, twenty-three with ADHD — sensory differences on low registration, sensation seeking, movement, vision, touch, hearing... and not taste and smell. Then last year, over a hundred Italian adolescents, half with ADHD, and they found differences on every component and every modality, taste and smell included. One says the smell channel is in, one says it's out.
So the honest answer to "is this a documented ADHD thing" is "ask me again in five years."
Or "both, depending on the population and the questionnaire." And there's a wrinkle on top — a pilot study with adults found over-responsivity was only marginally higher in ADHD and stopped being significant once you accounted for anxiety. Some of what reads as sensory sensitivity is anxiety wearing a sensory costume. Not saying that's Daniel — his error log is pretty mechanical, not emotional — but the population picture is muddy.
Here's the finding I want to put at the centre, though, because it's the one that reframes everything. Twenty eleven, twenty-nine adults with ADHD, twenty-nine matched controls, put through the full Sniffin' Sticks battery.
Schecklmann, yes. Sensitivity, discrimination, identification — no difference. The ADHD group smelled exactly as well as everyone else.
And then they did brain imaging while people smelled things, and the ADHD group showed diminished activation in the olfaction-associated regions. Same nose. Different handling.
The nose is fine; the filter isn't.
That's Daniel. He's not a bloodhound who's cursed with smelling everything. He's got a brain that allocates attention to smell differently — and only when it matters, only during effortful work, which is exactly what his litmus test shows.
And it squares with the kids' literature too, which cuts both ways. Unmedicated children with ADHD have shown lower odor detection thresholds — sharper noses — while medicated ones look like controls, and other studies have found impaired identification and threshold in the other direction. The channel itself is a moving target. The allocation story is the stable one.
One more piece of the naming answer, then. Autism.
Right, because this is where the smell question has actually been carved up properly. A couple of years back a group cluster-analysed sensory profiles of six hundred autistic people, children and adults, and got five distinct phenotypes. One of them is literally called taste and smell sensitivity. It's a named cluster. So the concept of a distinct smell-sensitive sensory profile is real and established — in autism. In ADHD, it's still an argument between two papers.
Which, for a man who asked us to name it, is a slightly deflating answer.
The name exists one lane over.
If the nose is fine and the brain is allocating attention differently, the obvious next question is whether smell actually distracts like sound does. That's the parallel he claims. Does it hold up?
On the sound side, rock solid. This is the irrelevant sound effect — task-irrelevant background sound reliably damages verbal short-term memory, and the bit that matters is the changing-state effect from Jones and colleagues in ninety-two. Sound that changes from one moment to the next disrupts serial recall far more than a steady repeating sound. A tap dripping the same drip forever is one thing; a conversation changing state syllable by syllable is another. And Hughes's group in two thousand seven showed there are at least two separate hijack routes — one interferes with the ordering process itself, one grabs attention by being a deviant, a sudden change.
Serial recall — keeping a sequence in order. That's a lovely match for Daniel's litmus test, actually.
It's almost embarrassing. Losing your train of thought, punctuation in the wrong place — order errors, sequencing errors. And the changing-state finding makes a testable prediction for Daniel's own kitchen. Coffee brewing is a changing-state event. It starts, it develops, it peaks, it lingers. Coffee that's been sitting in the air for an hour is steady-state.
So the prediction is that Hannah turning the machine on should cost him more than the room still smelling of coffee an hour later.
That's the prediction. And it's one Daniel can check at his own desk, no lab required. I'd like to know.
Now the smell side. You've got the sound literature nailed down. What's on the other side of the scale?
A fraction of the volume, and it points in every direction. There's a study from two thousand five that kills me. Two odors. The first, a mustard-oil irritant, increased the amplitude and duration of attentional capture. The second, phenylethyl alcohol — that's the rose note, and it's all over coffee aromas too — abolished capture entirely, but slowed information processing across the board. One odor sharpens the hijack, another one cancels it and charges you a speed tax instead. Opposite directions from two molecules.
So whichever one you've got in the kitchen, you lose.
Then there's a working-memory study, eighty-odd adults, pleasant odor, unpleasant odor, no odor. Only one of three working-memory tasks moved — spatial span — and only under the unpleasant one. So valence matters, and the effect is narrow. Same picture in a visual working-memory study: weak smell and sound distractors didn't move overall performance, but distractors rated negative drove error rates up.
Negative smells grab harder than pleasant ones. Daniel says he's not that fond of coffee — that might be doing half the work.
Could be. And then there's the part where the literature eats itself. Colzato's group reported peppermint widened the attentional blink relative to lavender — odors changing temporal attention. Last year a German team tried to replicate it in three separate experiments and found nothing. No evidence these odorants touch the attentional blink at all.
Three experiments of nothing.
Three. And the cross-modal work says visual stimuli dominate olfaction when they compete — one paper calls smell a primitive channel whose job is detecting hazardous chemicals by alerting attention, and then shows it loses to pictures. The lab says vision beats smell. Daniel's desk says coffee beats everything.
What about the animal side? That's usually where the clean version lives.
It is. Harvard work in Nature Neuroscience — mice identifying a target scent against background odors. Eighty-five percent accuracy or better when the background was clean, and performance fell as background odors piled up. Background odor degrades signal detection, in a nose-first animal. That part of the general claim is real.
So the parallel holds in outline and fails in the paperwork.
That's a fair compression. And the specific gap — nobody has put smell-based and noise-based distraction head to head on the same task in the same people. Nobody has tested Daniel's uncharacteristic-errors signature as a marker of anything, either. The serial recall literature measures errors in the right family, but the self-monitoring version he invented for his own desk has never been validated. Which is a shame, because it's a good instrument.
He built a better outcome measure than most studies use, over breakfast.
Well, before we get into all that, let's go to the phone. Mum, are you there?
Hello dear, it's your mother. It's time for Dorothy's History of Toast.
Apparently raising a glass is called a toast because people used to put a piece of spiced toast in their wine or ale. And Falstaff asks for a quart of sack with a toast in it, in Shakespeare's The Merry Wives of Windsor.
It's true, but it does make you sigh. You put something nice in the drink and it just goes soggy, doesn't it. Nothing stays as it was.
Anyway, sweetheart, I've got a load of washing to hang out before the rain comes. Give my love to your brother. Bye bye now.
Give her our love back, and tell her the Shakespeare checks out.
She'll be delighted. Where were we — the apartment.
The apartment. So if smells are changing-state events, the question is why a small apartment amplifies them, and that part is solid physics. Cooking emissions in a compact flat have nowhere to go. A test-kitchen study from a couple of years back compared recirculating hoods against extracting ones — the ones that pipe air outside versus the ones that filter it and blow it back.
And recirculating lost.
Worse than lost. The recirculating hoods produced higher occupant exposure to volatile organic compounds, partly because the activated carbon filters removed ethanol poorly and then desorbed it when the hood was switched on. The filter becomes a source. You install a device to remove the smell and it hands the smell back to you.
A machine that makes the problem it's paid to solve. You'd run for office.
And here's the detail I love — the airflow rate barely matters. They compared a hundred and eighty cubic metres an hour against two hundred and fifty and found no meaningful difference in capture efficiency. Above three fifty, marginal gains. People fight about fan power; the carbon is the argument.
What's the actual floor? Norway tends to have opinions.
Norway's minimum is a hundred and eight cubic metres an hour, and SINTEF tested hoods at that rate and reported they didn't capture enough of the cooking pollution. Their phrase. Recirculating solutions were far worse again for gases and ultrafine particles. So Daniel's missing extractor fan isn't a minor inconvenience — it's the difference between a sink and a source. Though even a good fan only works if you use it. Sensor study in one-bedroom apartments, four rooms instrumented — people turned the hood on for barely two-thirds of cooking events.
A third of the time the solution is standing there, off.
Standing right above the pan, doing nothing, like most solutions.
One caveat before we go further — this literature measures exposure, not attention. Particles and VOCs and health outcomes. Nobody has measured cognitive distraction as a function of ventilation. His detached-house theory — smells never became issues because they had somewhere to go — is well supported as an exposure story and completely untested as a cognition story.
Which is his actual question. Fair.
So let's take up the split, then. Adapting the environment against working on himself. He says he's drawn to the second, and I think the honest reading of the evidence is that it lets him down.
Here's what surprised me, though. Start with the clinical side — occupational therapy is where this lives for adults with ADHD. The UK Adult ADHD Network consensus statement on OT for adults with ADHD. And what do they propose OTs do? Help adults monitor and regulate sensory stimulation, recognise their hyper- and hyporeactivity, and use strategies like movement breaks, headphones, workplace adjustments. It is wall to wall environmental. Managing input. Not one line about desensitising anybody.
The professionals whose entire job is the person's nervous system keep prescribing changes to the room.
And the sensory diet concept — the personalised schedule of sensory activities — is explicitly framed in OT practice as not about fixing sensitivity but about providing appropriate sensory input to maintain optimal arousal. They're not even pretending to fix the person. Regulation, not cure.
Though the evidence behind all that is thin.
Honestly, yes. Reviews of sensory diets say the current evidence is limited and the results are mixed. A Swedish systematic review concluded OT interventions may improve occupational performance for adults with ADHD — may — with more research needed. The scoping review of sensory modulation interventions for adults with mental illness didn't even include ADHD. The whole treatment literature for exactly Daniel's situation is a few rooms of furniture.
So the clinical side is weak but unanimous in direction. Now the habituation side. He wants to believe he can get used to it. Can he?
There is real habituation research — prolonged exposure to an odorant does produce stimulus-specific decreases in sensitivity to that odorant. Stimulus-specific. You habituate to that smell, not to smells. And it recovers with time. You'd be re-training yourself against each individual thing Hannah cooks, forever, on a treadmill.
And the famous training protocols go the wrong way.
Completely the wrong way. Olfactory training — the Hummel protocol, twice-daily structured sniffing — is designed for people who've lost smell. Twelve weeks gets you, on the order of ten points on the composite TDI score, and reviewers argue even that's marginal. There's a training study where people gained sensitivity to a specific anosmia, and at nineteen-month follow-up nine out of ten were anosmic to it again. Even when it works, it fades. There is no established protocol on earth for decreasing your responsiveness to everyday odors in order to protect attention. Nobody has built that, because nobody thought the goal was legitimate.
The entire field is trying to help people smell more, and one man in Jerusalem wants to smell less, at specific times, and there's nothing in the cabinet for him.
So my read — his instinct that working on himself is the nobler path, the evidence doesn't back it. The environmental fixes have measurable exposure benefits and clinical consensus behind them. The self-work is stimulus-specific, temporary, or engineered for the opposite problem. Everyone does live in a smelly, noisy world, and that's true, but "just get used to it" isn't a strategy the biology supports — habituation is real, and the ADHD brain may simply be doing something different with the same input. Schecklmann again. If the filter is the problem, you fix the room the filter works in.
You're wondering whether we should buy him an extractor fan for his birthday.
The thought crossed my mind.
Don't buy a recirculating one.
You've been listening to the carbon-filter part of this episode very closely.
Someone has to hold the supplier to account.
Herman, one more thing on the airflow numbers before we leave the apartment. That airflow finding — do you think that's the same for a filter that's already saturated, or is the two-thirds capture number from fresh carbon?
Good question. The test-kitchen work was mostly fresh filters, and degradation over time is the variable nobody publishes happily. A hood that captures sixty-odd percent on day one is not capturing sixty-odd percent in year three, and there's no little light that comes on.
It's the carbon, not the airflow. You've got that the right way round, and I want it on record that the rest of the world hasn't caught up.
You've got a view on hoods, then.
I had one. In the flat before this one, a recirculating hood, a Regin model, cost me about four hundred shekels and I ran it for six years. I timed it. The kitchen smelled worse with it running than with it off. Onions at seven in the morning, fish, whatever Hannah across the landing had going. I wrote to the importer in February and got a coupon for a replacement filter, which I did not want, and a leaflet about airflow rates, which I already knew about.
You think it was desorbing.
I know it was desorbing. Six years of cooking came back out of that carbon whenever the fan ran. I replaced the filter once, in twenty nineteen, and the new one did the same thing within a year, which is when I stopped believing in the airflow argument. The filter from the old one is in the cupboard under the sink. I keep it. I take it out when tradesmen come, to show them what they're installing.
You show them the old filter.
They never look properly, Herman. One of them held it up to the light, which does nothing, and said it seemed fine. That was the last plumber I had in. I do the maintenance myself now. Corn said the same thing on air two minutes ago, more slowly, and I agreed with him then too.
So the advice is extracting, not recirculating, and never a used filter.
Get the one that goes outside, and check where the duct actually ends, because mine went into a box behind a soffit that the previous occupant had painted shut. I still say the fitters I've met are honest men doing a job nobody checks. Most of them want to do it right, and the ones who don't usually got that way from customers who never came back about anything.
He checked where the duct ended. Painted shut. Of course he did.
To be fair, that's the single most useful detail anyone's given us on this topic, and it came from a cupboard.
The thing about the filter is he's not wrong about the desorbing, which is where we came in. So where does that leave Daniel? The changing-state prediction he can test himself — whether the coffee's onset costs him more than its lingering. The adult ADHD smell question stays open, and nobody has run the head-to-head, same task, same people, smell against sound.
And if Schecklmann's read is the right one, the interesting question isn't how we desensitise anyone. It's how you protect effortful cognition from changing-state olfactory events. The ventilation people and the attention people have never once asked that together.
Two literatures, one kitchen, no shared citation.
Somebody's thesis is sitting right there.
Reviews, if today's episode earned a place on your list — five stars, the usual. And thanks as always to Hilbert Flumingtop, producing this and everything else we do from behind that desk, old filter and all. For more along these lines, there's episode twenty-five sixty-five, Why Background Conversation Hijacks Your Focus; episode thirty-seven twelve, Can You Train Your Nose to Ignore a Scent You Hate; and episode twenty-six twenty-five, White Noise vs Pink vs Brown. This has been My Weird Prompts. Rate us, review us, and tell a friend — and check out the archive at my weird prompts dot com.
See you tomorrow, brother.
See you tomorrow.