Turning, turning, turning through the years...

A paper published this week* suggests five key turning points that define distinct epochs in brain development. So where are our audiences on this new roadmap?

2,500 years before Batman, Spiderman (and Martin Lewis) Theban Superhero Oedipus made his entry into annals of The Business of Pleasure by allegedly solving The Riddle Of The Sphinx, which went something like:

“What creature has four legs in the morning, two in the afternoon and three in the evening?” 

The answer, for which Oedipus gained the Keys To The Kingdom (including, regrettably, the dead bolt on the Royal Bedroom) was, of course, Man:

“Crawling on all fours as a baby, later walking upright, and finally needing a stick to help them along.”

Flash forward two thousand years and the West Midlands Chapter of The Business of Pleasure expanded the ‘Ages of Man’ to a mystical seven:

..At first, the infant, Mewling and puking in the nurse's arms;

Then the whining schoolboy, with his satchel

And shining morning face, creeping like snail

Unwillingly to school. And then the lover,

Sighing like furnace, with a woeful ballad

Made to his mistress' eyebrow....

Until, too soon, the creature turns full circle:

The sixth age shifts

Into the lean and slipper’d pantaloon,

With spectacles on nose and pouch on side;

His youthful hose, well sav’d, a world too wide

For his shrunk shank; and his big manly voice,

Turning again toward childish treble, pipes

And whistles in his sound. Last scene of all,

That ends this strange eventful history,

Is second childishness and mere oblivion;

Sans teeth, sans eyes, sans taste, sans everything.

And while it may feel to some of us in The Business of Pleasure like that subsequent edition of The Human Roadmap, the concept of 'generation cohorts,' originated way back in Ye Olde Citye of London, while Will was still dipping his quill, it was actually some 500 years later that Hungarian sociologist, Karl Mannheim, conducted a thought experiment to ask why societies change and came up, by chance, with one of the first social science frameworks for defining generations:

‘Mannheim described generations as socially constructed groups of individuals of a certain set of ages that are defined by historical and social events (e.g. political turmoil, war, economic crisis). In other words, a generation is created when specific and impactful historical events cause the members of a range of birth year cohorts to view, interpret, or perceive the world differently than members of another generation.**

 However:

‘…Mannheim’s framework was about studying societal change, not identifying, measuring, and looking for generational differences; generations were simply a convenient way to describe the mechanisms of such change..’

So step forward The Business of Pleasure once again to pick up the idea and run with it, when, forty years later, Chicago playwright and theatre director, William Strauss, teamed up with Californian author and sociologist, Neil Howe, to propose that:

‘Generations are made up of non-overlapping, “cohort group(s) whose length approximately matches that of a basic phase of life, or about twenty-two years” a definition that that more closely aligns with the biological generational timeline. Because Mannheim’s approach meant that any number of individuals might not be part of a generation and that a generation could include many more or fewer than 20 years depending on when impactful historical events occurred, the Strauss and Howe approach, with its clearly-defined birth-year range of cohorts gained acceptance among researchers and the popular press.  The certainty of generational breakpoints delineated by Strauss and Howe, the specifically identified historical events, and the culturally germane generational labels they offered made their approach more appealing to social science researchers, marketing firms, and survey research organizations. Accordingly, by and large, these groups adopted features including the time frame (approximately 20 years), labels (Traditional, Boomers, Xers, etc.) and important historical events that defined generations (e.g. the Great Depression, Vietnam, the September 11^th terrorist attacks, the 2008 recession), even if the group cut off years and events were relatively arbritrary.

Unfortunately, adopting the Strauss and Howe approach was no panacea for what ailed the conceptualisation of research about generations. In both the Mannheim and Strauss and Howe approaches, generations are said to emerge when impactful historical events during key developmental periods, typically during the formative years of late adolescence and early adulthood, leading to the creation of shared memories and reactions that impact shared values, beliefs and even personality characteristics among members of each generation...”

Which is perhaps not the most outlandish attempt at human categorisation known to history. A mere 1500 years before Oedipus, a bunch of Babylonian star-gazers tried to divine the intentions of the Gods by joining the dots in the Heavens (somehow finding a plough, a crab, a scorpion, etc) and this Bronze Age Mesopotamian Start-Up, a.k.a. Astrology, was still hugely influential in Shakespeare’s day (and remains so in some postcodes).

But what are the ‘key developmental periods’ mentioned above?  And how will our understanding of the new Five Epoch Model impact on our understanding of our audiences?

The new research measured the ‘trajectories of changes in brain structure and function’ across roughly 4,000 subjects, of approximately equal gender split, and aged between new-born to ninety years of age.  The researchers then applied something called Uniform Manifold Projection and Approximation in order to render the huge mass of data easier to unpick.

EPOCH ONE (0-9 years old) “infancy into childhood.”

‘...The first turning point indicates that the childhood topological trajectory ends around nine years old. The first few years of life are marked by consolidation and competitive elimination of synapses and rapid increases in grey and white matter volume. Our results indicated that, topologically, structural networks develop along the same dimensions from birth until about nine years old. This is consistent with a previously identified cortical turning point around seven years old, where global efficiency reaches a minimum, cortical thickness peaks, and cortical folding stabilises…’

EPOCH TWO (9-32 years old) “Adolescence.”

'...While adolescence begins with puberty, the end of adolescence is less clear, with older definitions ending before 20 and more recent definitions extending into the 20s. The transition to adulthood is influenced by cultural, historical, and social factors, making it context-dependent rather than a purely biological shift. Our findings suggest that in Western countries (i.e. the United Kingdom and United States of America), adolescent topological development extends to around 32 years old, before brain networks begin a new trajectory of topological development. Additionally, 32 years old is the strongest topological turning point of the lifespan. At this age, the most directional changes and a large shift in trajectory occur compared to other turning points...'

EPOCH THREE (32-66 years old) “Adulthood”

' After age 32, the longest epoch begins, covering three decades of adulthood until age 66. Compared to the rapid maturation in earlier life, changes in network architecture slow during this period, which is consistent with our results that there are no major topological turning points until the 60s. Aligned with the slowing of white matter maturation during this period, the patterns of topological change are less complex than previous epochs, with clear increases in segregation and decreases in efficiency. This period of network stability also corresponds with a plateau of intelligence and personality. Consequently, not only do we observe the alignment of turning points with significant anatomical and cognitive milestones, but also the stable topological epochs of life coincide with periods of anatomical, cognitive and behaviour consistency.’

EPOCH FOUR (66-83 years old) “Early aging.”

‘Consistent with past work, we find no directional changes in network organization occurring at this age… Topologically, we find that during this phase macroscale reorganizational patterns simplifies -with the most distinct change being increasing modularity… Additionally, the early 60s mark an important shift in health and cognition in high income countries, such as the onset of dementia and hypertension. Hypertension, characterized by chronically elevated blood pressure, is linked to cognitive decline and accelerated brain aging and is also a known risk factor for dementia. Thus, as with the first two turning points, age 66 also aligns with significant shifts in health and cognition.’

EPOCH FIVE 83-90 years old “Late aging.”

‘..The last turning point marks a distinct decline in the age topology… It is possible that the lack of significant findings reflects the small sample size (93 subjects), which is reflected in the low statistical power in this epoch. However, when considering the significant correlations from previous epochs, a declining trend appears after middle age; epoch three had 11 significant correlations, epoch four had four significant correlations, and epoch five had one significant correlation. Therefore, this could reflect a true weakening relationship between age and structural brain topology in late life...’

Although this new research is focussed on only one key measure of development, observed changes in brain topology over time, to me it begs the question as to whether there might be a case for simplifying the traditional age brackets applied to audiences, audience research and behaviours to something like:

16-31,

32-65,

66-83

83+

DT                                                                                                                                                             

29 November, 2025 (60+) 

*Topological turning points across the human lifespan Alexa Mousley, Richard A. I. Bethlehem, Fang-Cheng Yeh & Duncan E. Astle Nature Communications November 25 2025

**Are generations a useful concept? David P Coastanza, Cort W. Rudolph, Hannes Zacher Acta Psychologica, November 2023