Can you remember a time when you find that you have arrived somewhere - only to realise that you have no memory of the journey?
This common experience shows that our brains can run on 'automatic pilot', taking us through life's familiar routines without bothering to link up with our conscious attention.
The two most common reasons for this are stress on the one hand, and boredom on the other. Stress over-stimulates us and can disrupt our ability to attend to the world. Given that attention is the gateway to memory, this is why some of these memory blanks often happen during periods of stress or worry.
But we can also travel on automatic pilot not because we are stressed, but because our minds have wandered due to lack of stimulation and challenge.
This is an example of a common feature of how our brains work - the so-called 'inverted U' shaped curve where we function at our best - remembering our journey to work for instance - when there is an optimal, medium amount of mental stimulation.
Some people use their vacations to reduce the overstimulation of a stressful life, and the classic ultra-restful, do-little routines of a familiar vacation location can be a great way of lifting you back up the inverted-U curve to regain some of your mental sharpness and energy.
But others look for stimulation in their vacations, searching for new sights, sounds and smells that might spark new ideas and fresh approaches to ways of life that may have come to feel a little jaded.
But sometimes this does not work very well. We fly to somewhere potentially stimulating - Paris, London, New York, Rome, Rio or Chicago - and we trudge round the sights that we have probably seen many times on television or movies, ticking them off one by one.
And we fly back home, maybe stimulated and refreshed, but perhaps also exhausted and overwhelmed by a mental slideshow of disconnected scenes, buildings, paintings, streets and a rag-bag of random historical facts. The memories of the vacation can end up as a sort of vague and blurry image.
Blurred memory comes from blurred attention and both can arise when we travel aimlessly, following not our own trail or interests, but rather a hotch-potch trail of sights appointed by tourist-marketing agencies.
We pay attention to - and hence remember - things, people and events that are linked to our own personal goals and interests. And this is why we will likely remember much more of - and hence be more stimulated and refreshed by - a journey with a purpose.
For some people, following a family-tree can yield such a purposeful journey, and that will expose them to people, places and events they would not have experienced otherwise. Novelty is very nourishing to the brain because it stimulates a neurotransmitter called norepinephrine which, in moderate doses, acts like a sort of 'brain fertilizer.' Curiosity exposes you to novelty, and curious people live longer and healthier lives, research shows. And one way of stimulating curiosity is to vacation with a purpose.
I know someone who had the brilliant idea of writing a travel guide with a purpose, which followed in the footsteps of Italy's most famous artist - Caravaggio. Let's Trail Caravaggio took me through Italy, Sicily and over to Malta in the tracks of the great, if troubled, Italian painter. The idea of this book was, rather than just going on vacation to Italy, make a journey that followed in the footsteps of Caravaggio, seeing not only his paintings, but the palaces, prisons and churches that played a part in his turbulent and amazing life.
I was left with a set of memories which seemed much clearer and more distinct than previous vacations. I love travelling, but having a purpose to my journey took me to places - both physical and mental - that no ordinary journey would have led me to.
One moment was to step out of the sweltering August heat out of the near-deserted Naples streets into the cool air of the vast, echoing emptiness of the Museo di Capodimonte to spend an hour, totally alone, in front of Caravaggio's masterpiece the Flagellation of Christ. In no other gallery in the world have I been able to commune with the spirit of a genius in such utter peace and solitude.
Another was to find a restaurant in a tiny Roman back street that might have been the site of the Blackamoor Tavern, one of Caravaggio's haunts, where he famously rubbed a waiter's face in a plate of artichoke because the poor man told him to smell the dish to find out whether it had been cooked in butter or in oil.
Locating the brooding fortress in Palo where a desperate Caravaggio was locked up for a night just when he was on the cusp of re-establishing his fugitive life back in his beloved Rome, was another moment that only trailing the man could have yielded. Gazing up at the bleak grey walls of the fortress, the sense of doom that must have filled the sick artist as he stumbled out to find the boat and his roll of paintings gone.
To find myself listening to brilliant jazz on a hot evening in a cellar burrowed into the sea walls of the incredible Sicilian city of Syracuse was another unforgettable tableau - another crossroads of time and space that only trailing a great figure such as Caravaggio could have led me to. I'm definitely a convert to travel with a purpose.
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