The sensitive touch

As part of our homeschooling, we have been considering how our sense of touch works? Surprise number one, our fingers and thumbs are far more sensitive than our eyes?  This is because fingertips contain an abundance of sensory receptors. Sensory receptors are the neurons that send messages to the brain.

These receptors are all over our bodies and not only in our skin. They’re also found in our joints, muscles, blood vessels and even our internal organs. Every one of our sensory receptors responds to touch. They can detect light touch, firm pressure, stretching, temperature, pain, texture, and vibration.

When your skin makes contact with something, for example, sandpaper, the sensory receptors identify the roughness of the paper.  They then transmit this information through your body to your brain. The brain combines the information received in order to recognize that you have touched sandpaper.

Hard as nails?

Fingernails, unlike fingertips, are void of feeling.  However because each nail extends far beneath and behind the skin of the cuticle, our brain still recognizes when something touches them.  This is because nerves on the back of the fingers identify forces transmitted from the tip of the fingernail. The brain next combines the sensations transmitted from the nerves with those from the finger pad and cuticle. This enables the brain to determine the item touched and the force used.

Incidentally, losing a fingernail alters the sensations on the pad side of the fingertip.

Is the female touch more sensitive?

When I was in school, many moons ago, my science teacher asked the class a question. Who did we think had the finest sense of touch? Did we think men had greater sensitivity or women? The boys fell about laughing. They believed themselves to be much thicker skinned than girls. To the horror of the girls, the boys claimed that females are oversensitive in every area. Fueled by hormones, therefore, girls had to be more sensitive to touch too.

Our teacher winked at we girls before addressing our mockers, “So, you don’t think men are as capable with their hands then? Or are you attempting to prove that where there is no sense there is no feeling?”

Experimenting with touch

He then instructed each of us to make a template of one of our hands. Having cut them out, we measured the templates and placed them in a giant Venn diagram showing hand size. 

The diagram revealed that the girls on average had smaller hands and fingers than boys. However, a small number of girls had larger hands and vice-versa for the boys. 

Next, he instructed us to complete a selection of tests designed to measure touch sensitivity. The tests involved wearing a blindfold and pressing our fingertips against a series of cards. In the middle of each card was a number of small beads. On some cards, the beads were a small distance apart, but on others, they were closer together.  The question was simple. Could we identify how many beads were on the card simply by pressing a finger against them?

The results

 The results revealed that regardless of gender, the smaller the fingertips, the finer the sense of touch. All those with smaller hands were able to identify the number of beads on each card. Those with larger hands got a few questions wrong. Our teacher suggested this was because the sensory receptors were closer together on smaller fingers.

You can test this theory by pinching the skin on your fingertip. Next, pinch the skin on your elbow. You will notice that your elbow is far less sensitive to pain? This is because small fingertips contain a larger number of sensory receptors than the skin on our elbows.

When an area of the body has more sensory receptors there is also a larger portion of the brain dedicated to receiving their signals. This, in turn, means greater sensitivity.

Here’s some home school fun

You will need

  • Pencil and paper
  • ice cubes
  • paper clips
  • a willing victim

Preparation
First prepare the paper clip by bending it into a U-shape. Try to keep the tips approximately half an inch apart. Be sure to keep the ice cubes in the freezer until needed.

Procedure
Your willing victim will need to close his or her eyes. Use a blindfold if you suspect they might peep.

Explain that you will be touching different areas of their hand and arm using a paper clip. Assure them you will not be stabbing them with it.  All they will need to do is let you know whether they can feel one point or two.  

You are going to begin by touching the back of their hand with your paper clip. Be sure that both tips of the paper clip touch their hand at the same time.

Did they feel one point or two? If they felt only one point, bend the paper clip U a little bit wider apart and repeat the test.

You are going to record the smallest distance between the points when your volunteer feels the two points. They are more sensitive to touch when the distance between the points is smaller.

Repeat the test again. Touch a fingertip, elbow, wrist, back of the lower arm, front of the lower arm and so forth. Where is your volunteer most sensitive?

Now switch roles with your partner. Are your findings the same?

Try repeating the test but first hold an ice cube on the testing area, for about ten seconds.  Is the area more or less sensitive now? If there is a change, why do you think it occurred?

Thumb sucking 

Given that the mouth and our fingers are both filled with sensory receptors we can begin to understand why thumb sucking comforts a baby. The messages to the brain do not involve pain and they are coming from two of the most sensitive parts of the body. 

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