APERITIFS ARE MORE THAN just an aesthetic or psychological stimulant of the appetite; there is solid science that shows they set the body up for the food in a physiological fashion and they do this in various ways.

Many alcoholic drinks have evolved from herbal medicines made from plants that were, rightly or wrongly, thought to aid digestion and/or cure so many gastric complaints. Wormwood, gentian and cinchona crop up in so many of them, along with countless other leaves, roots, fruits and barks that were macerated, extracted, fermented and/or distilled. A characteristic of most of these is their bitter taste.

Bitterness is a taste that crops up in many aperitifs; it is also an indicator of poison. If we ingest poison our bodies are wired to get rid of it as quickly as possible so, in response to the sensation of bitterness, warning signs from the brain tell the digestive system to ramp up into action. A complex series of physiological responses kick in: as well as making us salivate, bitterness triggers the release of endorphins to speed digestion and adrenaline to break down toxins in our stomach. These are warnings of possible danger ahead – they also raise our heart rate and make us feel heady and pleasantly high, which is probably why humans are the biggest risk-takers in the animal kingdom. We flirt with danger because it gives us a frisson of pleasure; we like bitterness in drinks because it smacks of menace.

But it is not only bitterness that makes a drink an effective aperitif. Alcohol itself clears the palate by rinsing molecules lingering in the pores on the surface of our tongues – it is particularly effective at dissolving stubborn non-water-soluble fats – thus encouraging digestion-aiding salivation.

Neat vodka is probably the most effective palate cleanser though hardly the most pleasant to drink, which is where a fizzy mixer comes in. The tingling sensation of the bubbles on your tongue also encourages salivation as well as a sense of cleansing, and the smaller the bubbles the more effective this is.

Carbon dioxide – the gas that makes bubbles – is more soluble in alcohol than it is in water, so the bubbles are smaller than in soft drinks (champagne and other fizzy wines, take a bow), although the sugar in tonic water and other mixers helps to stabilise the bubbles and so give the required effect.

There is some confusion as to whether fizzy mixers make the alcohol hit the bloodstream faster than if it was drunk neat. While there is some evidence that this is the case, sugar is known to slow absorption so it may well cancel out the effects of the bubbles. This is why sugar-free mixers appear to speed up drunkenness: another good reason, as if the taste wasn’t bad enough, not to drink diet tonic water. Sugar releases dopamine, a neurotransmitter associated with reward and pleasure, into our bloodstream, while artificial sweeteners do not. Artificial sweeteners also bond tightly to receptors in our taste buds and leave that distinctively unpleasant metallic aftertaste that’s hard to wash away.

Too much sweetness deadens the appetite, as does too much umami, that deeply savoury fifth sense we associate with Marmite, parmesan cheese and soy sauce, which is why a Bloody Mary, with the sweetness of the tomato juice set against the savoury seasonings, so often seems like a meal in itself. We in the restaurant trade used to call Saturday morning Bloody Marys ‘electric soup’: just enough alcohol to give the required lift and enough sustenance to keep hunger pangs at bay until our post-lunch-service grub. Sometimes we’d have another, just to keep us going.

Astringency and saltiness also make you salivate – fino and manzanilla sherry, for example, or dry white wines, or anything garnished with lemon or lime – so it’s no coincidence that much of the food that’s so fitting with aperitifs echoes these sentiments too – think roasted nuts, a modest crisp, slivers of salty cheese and/or salami, an olive or even a pickled egg still tangy from its brine.

All our senses are engaged when we drink.We use our sight to assess the initial demeanour of what’s in store – is it pretty and pale, perhaps with bubbles, or is it something tantalisingly dark and brooding? Is it served straight up, glorious in its nakedness, or does it come over ice with a compelling garnish? Does it look like something we’d like to drink?

Our sense of smell gives us more of a clue as we raise the glass to our lips; we always get the aromas – what those in the booze biz call the ‘nose’, never the ‘bouquet’ – before we get the taste. Fruity, floral, grassy, herbaceous, with notes of spice, nuts, smoke and/or leather, perhaps something redolent of a farmhand’s armpit after a heavy night on the hooch and a roll in the hay?

While our gustatory receptors (taste buds) on the tongue, the walls of the mouth and in the alimentary canal (yes, our stomachs have taste buds too) identify the five primary tastes – salt, sugar, sour, bitter and umami – it is our sense of smell that gives us the critical nuances of whatever we’re drinking.

The aromas travel through the nose and the back of the throat to reach our olfactory receptors. These can detect thousands of flavours, which is why what we smell is intricately linked with what we perceive as being taste. Touch is no less important. A glass should sit comfortably in your hand, giving a sense of pleasure from the balance between the weight of the vessel and the liquid it contains. When that liquid hits your lips it should do so with as little interference as possible, and this is where the rim comes in. Take a nice wine glass and pour in a drink – anything, even water, will do – then taste it. Do the same with a jam jar and you’ll see what I mean. Jam jars should only be used for jam, pencils or tadpoles, regardless of what the hipsters say.

Just as eating from a wobbly paper plate with a plastic knife and fork somehow diminishes the pleasure of the food in question, so drinking from an inadequate vessel will lessen the pleasure of your chosen libation. Plastic’s kind of fine for a picnic (though it’s so easy to sling in some sturdy tumblers wrapped in a couple of tea towels, it seems unnecessarily masochistic, not to say expensive and environmentally irresponsible, to pick plastic instead) but there’s something rather mean about them when they hit your lips. Also, they are wont to crack, with disastrous consequences, should you grip them too firmly. Paper’s also okay in an emergency, though it has a tendency to go floppy after a while when a firm grip can also lead to unfortunate spillage.

As for sound? Most of us recognise our own Pavlovian responses to the sound of ice clinking in a glass, the jolly ‘psst’ as we open a can of tonic or the arousing pop as we tease the cork from a bottle of champagne, and there is science to prove that sounds do indeed get our digestive juices flowing. Light and tinkling music will heighten sweet and creamy sensations while deep and mellifluous music will enhance the bitter and the dry. The volume of background noise has an effect too – a staggering 27 per cent of all drinks ordered on aeroplanes are tomato juice (with or without vodka). The 80 or so decibels of noise in an aircraft’s cabin interferes with our ability to taste sweetness, while it enhances our perception of savoury umami, so makes the tomato juice taste extra good. Tannins and acidity are also more pronounced in a pressurised cabin flying at 30,000 feet, why I never drink wine on aeroplanes; if I fancy a little tincture after takeoff I always go for a G&T. A much-travelled and much-lauded bartender sagely said to me, ‘As long as there’s plenty of ice and the tonic’s not Britvic, it's really hard to fuck up.’

At the end of the day, the brain is the only sensory organ we have; how we perceive what we are drinking is all in the mind – literally. The brain takes messages from receptors in all the sensory organs, and filters them through the darkest corners of our memories and personal predilections to give us our ‘sense’ of what we are drinking. It is so much more than what we see, smell and taste.

There is a famous, much-repeated experiment whereby subjects are given two glasses of wine, one white, one red. They are asked to describe the aromas and tastes of the wines, and to hazard a guess at what they are. The schtick is that they are the same wines, the red one being merely tinted with a tasteless colouring. The results are consistently extraordinary: those who fancy themselves as wine buffs use words such as ‘fresh, crisp, floral’ when describing the white wine (words so frequently found on professional tasting notes), then slip into ‘red fruit, spices, pepper and leather’ when they’re tasting the red.

Those who have very little experience of drinking wines fare the best – in one tasting a self-confessed wine hater said immediately, ‘they taste the same to me’. On another occasion a renowned South African winemaker was given the ‘red’ first – he was puzzled, certain that it wasn’t South African or even New World, then contemplated it still further and suggested it might be Italian, possibly from Piedmont. Then he sniffed the white wine and recognised it immediately. ‘That’s my wine,’ he said. ‘I made that.’ He’d been smelling and tasting the same wine.

It is said that the reason we chink glasses to toast when we’re drinking is that the sound completes the full sensory circle. (I’m all for enthusiastic chinking but a small word of warning here: chink bowl to bowl not rim to rim; this minimises the danger of breakage and also gives the best ringing noise). Sight, smell, taste, touch and sound join forces: all the senses are engaged and are woven together to deliver the full glorious experience of what drinking can and should be.