transcript of episode 25: FLATTENING THE CURVE, 25th February 2022
welcome to the error bar: reading tabloid brain science so you don't have to
in this episode: how your brain is just as good at age 60 as age 30, the neural correlates of near death experience & the most interesting questions in the whole of science
here is the brain news on the 25th February 2022:
[🎶 BIG BEN BONGS 🎶]
BRAIN DOESN'T SLOW DOWN UNTIL 60
in a story likely comforting to middle aged scientists & journalists, the Guardian & Independent reported last week that, Good News: the brain does not slow down until we are aged 60. what did they mean?
the result comes from a quite complicated analysis of an enormously huge set of data. a social psychology project in the USA has collected nearly 2 million responses from people who were asked to categorise things on a computer screen as, for example, 'good' versus 'bad' or as 'black' versus 'white'. they did this 120 times each.
in general, the results of this so-called 'implicit association test' are able to reveal people's unconscious attitudes - in this example, that white things are good & black things are bad. this test is a classic & it relies on people responding as quickly as possible.
in the new study, researchers in Germany downloaded 1.8 million test responses from the free online database. they analysed how people's responses changed as they age, from 10 to 80 years old. using some sophisticated (& unnecessarily complicated) analyses, the researchers reported that, while the total time spent doing the task changes a lot over life, one conclusion is that, in fact, our 'mental processing speed' remains good & strong until age 60.
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does mental speed stay high until age 60?
this is not a hard one. with a total of nearly 1.2 million responses, all openly available online & clearly-presented in this paper, it is a fantastically-simple task to fact-check this claim. all we need to do is look at the data.
i've annotated the image to accompany this story on the error bar website. what the image shows is a gradual & continuous increase in mental speed between age 10 to a peak at about 35, then a gradual & continuous decrease to age 80. it's true that the speed of change seems to be different at different ages, but the strong claim that mental speed is 'high & constant until age 60' is contradicted by just looking at the data.
how did it come to this? the error bar dug deeper.
first, this is a massive dataset - which is great - but quite a lot of data were removed, for example anyone performing the task without making errors was excluded. that's a bit odd, if the best responders are removed.
second, the task itself is quite subjective - is something good or bad? or is something black of white? - & although a well-studied task, it's just one task, so conclusions about mental speed in general must be extremely limited.
third, the data are not a good measure of mental processing speed. to test mental speed, we need volunteers to be fully-focussed & making responses as quickly as possible. but the authors included 'response times' as long as nearly 6 seconds, the average times were around 1 second & there were some massive differences between men's & women's responses.
fourth, one claim in the report is that the 'merely mechanical' processes of seeing the stimuli on screen & making the keyboard press response take as long as half a second in the oldest adults. this is a pure fiction - the study provides no sensible measurement of these sensory & motor processing speeds.
fifth, & amusingly, the authors chose a particular kind of deep, machine-learning analysis because they said it was "not possible" to analyse all the data in a different, simpler, but more computationally-expensive way. but the new analysis only took 32 hours to run on a computer, which makes me wonder how long the full analysis would take & why was there such a rush to get it done?
sixth & critically, the conclusion that mental processing speed is high and constant until age 60 relies only on the authors' choice of how to put a best-fit line on the data. the analysis used requires all the people to be divided into two or more different age groups. for error bar nerds: the data were fit with three straight lines for three age groups. but age is a continuous variable, so why did the authors not just fit a single, continuous curve?
well, listeners, i downloaded the data, sharpened Occam's razor & fit that single curve. it provides a very slightly worse explanation of the data, but that's what you would expected, as it is also a much less-complex explanation.
look at the data
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LIFE FLASHES BEFORE EYES
the Guardian & Daily Mail report the unique case of an 87 year old man who had suffered brain damage, received brain surgery, then deteriorated & died several days later. the medical team were recording electrical signals from his scalp to monitor his seizures when he had a heart attack. treatment was withdrawn & he died.
recording brain activity during death has not been reported before, which is what makes this case unique. the scientists analysed the available data in a number of ways & concluded that, just before death, there is a coordinated, coherent activation of the brain that is similar to what happens during memory recall, or in rats as they die.
while the Daily Mail concluded that our lives really DO flash before our eyes as death approaches, the Guardian took a fairer, more skeptical view.
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does our life flash before our eyes?
the Mail's story & perhaps the scientists' spin, claims that the coordinated brain activity happening around the time of the heart attack may provide evidence of his life flashing before his eyes. in the scientists' exact words:
"Given that cross-coupling between alpha and gamma activity is involved in cognitive processes and memory recall in healthy subjects, it is intriguing to speculate that such activity could support a last â€œrecall of lifeâ€ that may take place in the near-death state." p9
yet in the discussion section, the authors (were probably forced to) note that the patient had suffered brain damage & seizures, that he was on strong brain-altering medication, that he was unconscious & unresponsive at the time.
perhaps the patient's life flashed before his eyes. or perhaps he passed peacefully in his sleep. we will never know.
maybe speculate less
and the brain in brief...
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PHYSICS & CONSCIOUSNESS ARE FUNDAMENTAL
science is very big. but as the error bar learnt last year, the science that makes good newspaper stories is really quite small. for brain science it's dogs, dementia, robots & consciousness; for physics it's black holes, dark matter, big bangs & life on other planets.
but if you ask a scientist on the street what are the big, unanswered questions & you'll likely hear about more than just consciousness & dark matter. for example, a biologist might want to know what causes cancer, or why there are no penguins in the northern hemisphere.
in the Irish Times, an Emeritus Professor of Biochemistry selects five unanswered questions from the whole of science. four of them are about space, one is about human consciousness.
email firstname.lastname@example.org with your unanswered question
it's closing time at the error bar, but do drop in next time for more brain news, fact-checking & neuro-opinions. take care.
the error bar was devised & produced by Dr Nick Holmes from University of Birmingham's School of Sport, Exercise and Rehabilitation Sciences. the music by Dee Yan-Kee is available from the free music archive. find us at the error bar dot com, on twitter at bar error, or email talk at the error bar dot com.ε