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Scientists sort the senses into special senses, which have their own organs (vision, hearing, smell, taste and balance), and general senses spread through the body, such as touch, pain, temperature and the sense of where your body parts are (proprioception).

Every sense uses receptors: cells or nerve endings that react to one kind of stimulus. Photoreceptors react to light, mechanoreceptors to pressure and vibration, thermoreceptors to heat and cold, chemoreceptors to chemicals and nociceptors to things that could harm you.

You are born with about 10,000 taste buds, on the tongue, the roof of the mouth and the throat. Taste cells respond to five basic tastes: sweet, sour, bitter, salty and umami (savoury, found in broth and some cheeses). Cells for each taste are spread across the tongue, not kept in separate zones.

Experiment: Does smell help taste?

1. Question: can you tell apple from pear just as well with your nose pinched? Write a prediction.
2. Work in pairs: a taster and a tester. The taster closes their eyes.
3. Nose pinched: the tester gives 6 pieces in a random order (3 apple, 3 pear). The taster chews each and says 'apple' or 'pear'. Sip water between pieces. Record right or wrong.
4. Nose open: repeat with another 6 pieces in a new random order.
5. Fair test: same size pieces, same fruit, same number of tries, eyes closed both times. Only the nose changes. Count the right answers in each condition and compare with the class.

Condition	Right answers (out of 6)	Class total
Nose pinched	Prediction: which will get more right?
Nose open	Prediction: which will get more right?

Questions

1. Explain the difference between a special sense and a general sense, with an example of each.

2. Why was it harder to tell apple from pear with your nose pinched?

3. Name two things you kept the same to make the fruit test fair.

4. Why can a fingertip feel finer detail than your arm?

Sources for every fact on this sheet: echoesof.science/school/senses/sources/

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