Practically the same things happen when we are tickled, and explains why you laugh when tickled. When some one tickles the bottom of your feet or your ribs or another part of your body it produces, in most cases, the same effect on the brain as the laugh-producing sound or sight, and arouses the same combination of muscles and nerves to activity. It is just like pushing the button of an electric bell. When you push the button the contact produces the spark which sets the machinery of the bell in motion and the bell rings and will continue to ring as long as you keep your finger on the button, or until the spark-producing power of the battery is gone. Then, as in the case of the bell, you cease to laugh, because the spark that produced the laugh combination is gone. That is why some things tickle some people very much and do not affect others. Some are not so sensitive to the laugh-producing combination as others. After the thing that tickles you has been going on for some time you are not tickled into laughter any more, because the impression on the brain ceases to be as strong. Why Don’t I Laugh When I Tickle Myself? Your mind tells you there is no need to laugh when you tickle yourself. Your mind will not respond to the tickling sensation when it is aware that the cause of the tickle is yourself. The reflex action of the mind which causes laughter and squirming when some one else tickles you only acts when it is not conscious of the cause. The whole purpose of the sensitive organization of our skins is to give us information and cause action which will enable us to protect ourselves when any outside influence touches us. An injurious touch causes shock and pain, and the harmless tickle arouses the laughing and squirming sensation. What Happens When We Laugh? Laughter is what we call a reflex action. When something occurs to make us laugh, whether it is something we see, or feel, or hear, it is because certain sensory nerves receive an impression in one of three ways, carry it to the nerve centre and the nerve centre then sends the same impression along certain efferent nerves, which connect with certain muscles or glands, and excite them to activity. The action is practically the same as when you hold a light before a mirror. The rays from the light strike the surface of the mirror and are reflected back from the surface, lighting perhaps corners of the room, which the direct rays from the light could not reach, all depending upon the angle of reflection. Light will always reflect from a mirror that is exposed to it.