We are hardly conscious of the sophisticated touch systems in our body. They allows us to feel pressure when we sit or stand, or to feel the texture of a plate with our fingers. We can work our mobile telephone and detect small changes in the temperature of the room. We can even keep track of where our organs and limbs are in space.
The different types of touch have evolved independently. What we call “touch” is in fact a whole series of separate systems. For example, there are two different types of neural pathways. One is slower than the other. They carry different kinds of information to different parts of the brain. One network carries messages on pain and temperature quickly. These are the stimuli most likely to signal danger. Evolution ensured they get to the brain quickly. The other carries the rest of our touch sensations, more slowly to separate parts of the brain.
Even that is a simplification. We humans do not process all the different kinds of touch in the same way. Our brains discriminate between interpersonal touch and intra-body touch as our bodies move. Our brains separate out extra-personal touch. That is the touch and feel of inanimate objects. Neuroscientists have shown that different kinds of touch trigger activity in different parts of the brain. Scanner data even shows that pleasant and painful “touches” have quite different effects.
Our sense of touch is based on a complex set of receptors. Fibres conduct the signals back over relatively long bodily distances to the brain . Our brain even corrects for the time lag between touching the wall with our feet and hands simultaneously. The signal takes longer to reach the brain from our feet. Intra-body receptors signal the position of our bodies, arms, and legs. This intra body network usually operates completely sub-consciously . It even understands where our internal organs are relative to each other.
“Phantom Vibration Syndrome”
Does your mobile phone vibrate but when you look it is a false alarm? Many people now use the vibration of their smart phones to signal the arrival of texts and emails. This appears to be leading to phantom vibrations. Seventy percent of doctors, surveyed in a study in the British Medical Journal, report phantom vibrations . Many reported one false alarm a day. Further investigation showed that the more the doctors used the vibration facility on their phones and pagers the worse the effects.
“Phantom Vibration Syndrome” is caused by the elevation of subconscious intra-body touches into consciousness. We probably have vibrations going on in our bodies all the time. Our intra body touch system will pick them up. Using vibrations as a warning signal on our smartphone changes the threshold of consciousness. We now need such vibrations to be in our conscious mind. The resultant confusion leads to the phantoms.
Our intra - body system can have other effects. Researchers in Florida have found that if you eat standing up the food will not taste as good. They found that pita bread, brownies, and fruit bars tasted less good when standing rather than sitting. Standing is suppressing the taste system. To prove this they created an identical brownie loaded with salt. When standing this “unpleasant” bar was rated better than when seated.
It has been known for a long time that standing up is more stressful than sitting down. It engages the intra-body touch network, sight and a whole set of muscle responses. That stress is what suppress our sense of taste. They also found that the results for a stool were halfway between standing and sitting.
Touching Our Food
There are other types of touch that we may not think of often. Touch plays an important part in the sensation of eating through “mouthfeel”. This is the touch that takes place in our mouths when we eat. The texture of the food helps us to determine its identity and is an important determinant of our liking . We are extremely sensitive to this touch. From an evolutionary point of view, it was a major part of our defence mechanisms. If food is too hot, has sharp edges or contains foreign objects, it is the touch in our mouths that warns us. Anyone who has tried to eat a fish bone will know just how sensitive this touch can be.
We are particularly sensitive to the feel of fatty foods. These are the kinds of foods that sustained us during our evolution. It is the “mouthfeel” of a yoghurt that tells us how creamy and thick it is and hence its quality. Quality perception does not necessarily come from our mouth alone. It is influenced by other kinds of touch. To produce “better” yoghurt, you do not need to change the recipe or the ingredients. Instead, all you need to do is engage another sense of touch. Just serve it in a heavy bowl and give people a heavy spoon.
Yoghurt was served to individuals in bowls that were visually identical to each other. The bowls did differ in weight. Respondents were asked to hold the bowls whilst eating the yoghurt with identical spoons. The heavier the bowl the more the yoghurt was liked. The heavier the bowl the thicker the yoghurt was rated to be and the higher its estimated price. Of course, the yoghurt in the bowls was identical, it was the weight of the bowls that made the difference. We associate quality with weight. This in turn influences our assessment of that food.
If you cannot change the bowls, then spoons will work just as well. In another study the bowls and the yoghurt were constant for everyone. All that changed was the weight of the spoons. One weighed five grams and the second was more than four times heavier at twenty grams. The results were just as impressive. The heavier the spoon, the higher the perceived quality, and the greater the preference.
If you want your yoghurt creamy you may also have to be careful about the texture of the bowls in which you serve it. When people ate a digestive biscuit from a container covered in a rough sandpaper texture, the biscuit felt crunchier and harder. A textured bowl will also makes potato chips taste saltier than a smooth bowl.
An Ageing Touch
Mouthfeel changes with age. Our sense of food texture changes. This can also come from changes in the mechanics of our mouth. The reduced ability to chew and the reduced saliva flow can affect our sense of texture. The sensitivity to creaminess, fattiness and elasticity of food reduces with age. Young adults seem to prefer rough, crispy, crunchy, and hard textures. Older adults prefer intermediate textures , rather than crunchy. Older adults do not prefer completely smooth or soft textures. contrary to many stereotypes.
One study used the same soup but at different levels of thickness. The thicker the soup the more younger people preferred it. For the " over sixty-fives" the thicker the soup the less they liked it. Restaurants trying to improve their offering for the healthy, Third Agers need to focus on the physical consistency of the food. It still needs to taste good.
Age will put even more stress on standing. Eating food whilst standing is more likely to have a bigger negative effect. Serving thick hearty soup to a group of standing Third Agers is unlikely to go down well.