He's racked up appearances in a blue jersey but evidently he’s still going through some growing pains as a Rangers player

There's a widely held misconception when it comes to the development of the adult brain.

Academics call it the “Mature at 25 myth”.

Essentially it states that the frontal lobe - the part that controls functions such as decision-making, risk assessment and impulse control - advances at a slower rate than the rest of your noggin.

And the disputed theory suggests that adulthood doesn’t begin until midway through your 20s, when your grey matter finally works out that agreeing to that daft haircut or getting blitzed in a nightclub when you’ve got work in the morning might not be the best idea after all.

It’s the reason why most car rental firms won’t hire cars out to teenagers. And why kids today find themselves having to sell a kidney just to afford the insurance premium on their first motor.

But in truth, boffins have established that brain development is a lifelong process and the rate it occurs varies from one individual to the next - it doesn’t simply stop once you blow out the candles on your 25th birthday cake.

For every 30-something boy-racer out there still zooming about in a souped-up Ford Fiesta with a wife and wean at home, there’s a 21-year-old working out his retirement plan based on a lucrative stocks and shares portfolio.

What does any of this have to do in the sports pages, you ask?

Well it came to mind this week after watching Rangers defender Manny Fernandez’s performance at Dens Park, when his decision-making and risk assessment skills certainly came into question.

He was out of position for both of the goals the Light Blues handed Dundee as they dropped two precious points on Saturday night. For Bradley Fink’s opener, he failed to sniff the danger and drop deep enough to offer backup protection for Dujon Sterling’s under-hit back pass.

And again in the second half, he was caught ahead of the ball when he should have been tucked in ready to deal with the danger when Dan Neil was next to leave Gers exposed. These are the kind of mistakes he’s made too often this season.

But having turned 25 back in July, some fans assume the big defender should have outgrown that kind of sloppiness by now. That claim, however, overlooks an important point.

While he may tower above the rest of the league at 6ft 4ins, the centre back is actually a relative tot in professional football terms. After all, he’d barely kicked a ball in the senior ranks down south until 2024 - the year before Russell Martin handed him a chance at Ibrox.

Before that, he’d started out at Gillingham as a trainee but found himself tumbling down rungs of the English pyramid before Peterborough finally plucked him from Ramsgate in the seventh tier. By the time the big Londoner joined Gers last summer aged 24, he had amassed just 60 League One appearances.

He’s almost up to the 50-mark in a blue jersey but evidently he’s still going through some growing pains as a Rangers player. Both Fernandez and his boss Derek McInnes have candidly admitted that the No1 issue he must address if he’s to fulfil his potential is his focus levels, and again, that was evident at the weekend.

There’s no denying the huge physical attributes Fernandez boasts and when he has his mind on the job, it’s clear why Rangers have such high hopes for him. But to get the best out of him, Rangers need his concentration skills to catch up with his giant frame. And that’s why McInnes may be well advised to treat Fernandez like he would do with one of his hopeful youngsters.

Sir Alex Ferguson was famous for dipping pupils from the Class of 92 in and out of his team at Manchester United, using his vast bank of experience to judge when one cocky lad might need brought down a peg or two or the occasions when a timid character could do with a breather amid the suffocating pressure of a title race.

However, it was seldom an approach he took with his senior stars. But as discussed earlier, not everybody develops at the same rate and Fernandez in football terms has still to reach the stage where he can be considered a fully ripened figure at Ibrox. So for his own sake, it might be time to take the new Nigeria cap out of the firing line for a spell.

Rangers are no longer in the position they were last season when Fernandez finally got his big break in Danny Rohl’s starting XI simply because there were no other centre-backs fit. Ben Godfrey is waiting in the wings desperate for a chance to show he can rediscover the form that once had him winning England caps and starring for Everton in the Premier League.

Saturday’s game at home to St Johnstone appears to be as good as any to throw the on-loan Atalanta defender into action and see if he can motor along as smoothly as the Rolls Royce next to him that is Olwethu Makhanya.

As for Fernandez, a break may very well be the best thing, offering a chance to reflect on his growth so far and a moment to work out where he still needs to measure up. The experts at Transfermarkt claim he’s the most valuable player in Scotland with an anticipated price tag north of £16million.

That’s all down to his clear potential. But for that potential to be realised, he needs to mature into the player Rangers believe he can become.