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Several senses at once

How Does Touch Work?

Touch is really several separate senses — pressure, temperature, pain and stretch.

Pressure and vibrationTemperaturePainStretch and position
Four systems reported as one feeling.

  1. Step 1 of 5

    Different receptors do different jobs.

    A patch of skin Several distinctreceptor types

    Your skin has separate sensor types for light touch, deep pressure, vibration, heat, cold and damage. They just report together.

  2. Step 2 of 5

    Sensitivity varies hugely by area.

    Fingertipreceptors packeddenselyPalmmoderateBackvery sparse

    Fingertips and lips are packed with receptors; your back has far fewer. Two points a centimetre apart feel like one there and two on a fingertip.

  3. Step 3 of 5

    Your brain devotes space accordingly.

    Your actual body Proportioned normallyYour brain's map Giant hands and lips

    The brain map of the body is wildly out of proportion: enormous hands and lips, tiny back and legs. Area is allocated by sensitivity, not size.

  4. Step 4 of 5

    Receptors report change, not steadiness.

    1 First contact —strong signal2 Signal fadeswithin seconds3?You stopnoticingentirely

    Most sensors fire on change and then quieten. That is why you stop feeling your clothes seconds after putting them on.

  5. Step 5 of 5

    Pain uses its own fast and slow paths.

    Fast pain fibres Immediate — you reactfirstSlow pain fibres The dull ache thatfollows

    A sharp fast signal makes you pull away before you think; a slower dull one follows. That is why a stubbed toe hurts twice.

    The pull-away reflex is handled in the spinal cord. Your hand is moving before your brain has been told.

The short version

Touch is several senses at once, mapped in the brain by sensitivity, and most of it reports change rather than steady contact.

Try it yourself

Touch a back with two pencil tips 2 cm apart, then a fingertip. On the back it feels like one point.

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