How sensitive are you?

How sensitive are you?

Try this and find out!

What you need:

  • A willing volunteer
  • Two toothpicks

How to:

  1. Get your volunteer to close their eyes.
  2. Press two toothpicks, point downwards, lightly on the volunteer's arm - make sure they're around 5 cm apart. Don't press hard - that would hurt! Ask the volunteer how many toothpicks they can feel.
  3. Move the toothpicks closer together and keep asking the volunteer how many toothpicks they can feel.
  4. At a certain distance apart, the volunteer will only be able to feel one toothpick - even though there are two!
  5. When this happens, measure the distance between the two toothpicks. Record your results in a table like this:
Area of the body Distance between toothpicks
Arm
Hand
Index finger
Feet
Knee

Repeat the experiment on different parts of the body - you could try the back of the hand, index finger and feet - if they're not too ticklish!

What did you find?

On some parts of the body, such as the index finger, the distance between the two toothpicks should be much smaller. This means that the volunteer has more sensory receptors in that part of their body. Sensory receptors are specialised cells. They detect changes in the environment, called stimuli, and turn them into electrical impulses. In this case, the sensory receptors are detecting pressure. Sensory neurones - nerve cells - carry these electrical impulses to the spinal cord and brain.

To be really sensitive, each sensory receptor must connect to a different nerve cell.

To find out more about nerves, go to: What's in a Nerve?

Curriculum information

  • Summary

    Which parts of your skin contain the most touch receptors? This simple experiment helps test different parts of the skin to see which are the most sensitive to touch and so contain the most touch receptors.

    Curriculum key wordsOther web links
    • Sense
    • Touch,Nerve
    Interactive resource illustrating skin structure and function
    Illusions and tricks to fool the senses
    Science Curriculum Links
    National CurriculumCurriculum for excellenceNorthern Ireland Curriculum
    Responding to stimuli (KS4 Breadth of study 5d).Responses to external and internal stimuli (SCN 4-12a).Nervous system (GCSE Biology).