The first example in this chapter of the book is designed to illustrate both the integrated nature of the central and peripheral nervous systems and the complex chain of physical and biological processes that underlie even the simplest forms of behavior:

If your teacher asks you to raise your right hand at the count of three, and then lower it, you surely be able to do so. But how? In order for you to follow these simple instructions, sound waves from your teacher’s vocal cords have to travel through the air and reach your ears, at least one of which has to be in working order. These sound waves will enter your outer ear, pass down your ear canal, and strike your eardrum (tympanic membrane) which will then begin to vibrate. These vibrations will cause similar vibrations in a series of three small bones in your middle ear. Their vibrations will create waves in the fluid that fills a coiled tube (cochlea) in your inner ear and the motion of that fluid will bend tiny hair cells inside the tube. Each of those hairs is connected to nerve cells that travel together (as the auditory nerve) to the brain and the stream of combined messages from all these cells will stimulate the areas of your brain that receive sound. The pattern of stimulation provides information (sensations) about the frequency and intensity (pitch and loudness) of the stream of incoming sound.

But in order for you to understand (perceive) the sounds your teacher made, your brain has to compare them to information about the patterns of sound that are already stored in your long-term memory. If and when it finds matching patterns, you will be able to recognize the stream of sounds as a stream of meaningful words, in this case, the sentences that make up your teacher’s instructions. If the teacher had been speaking an unfamiliar language, you would have still heard (sensed) the sounds, but you would not have been able to recognize (perceive) meaningful words.)

But the story is not over. Now the action shifts to the frontal lobes of your cerebral cortex, where most of your higher cognitive processes occur, including thinking, planning, and decision-making. While holding the information about the teacher’s instructions in your short-term memory, you will have to retrieve information from long-term memory about what your cultural background and other aspects of your social learning has taught you about what is appropriate and inappropriate behavior in a classroom situation (including about complying with instructions and following social norms). On the basis of all this information, you will make a decision about what to do when your brain recognizes the sound of the word “three.” Assuming your decision is to comply, when you hear “three” you will have to execute that decision by remembering where the right side of your body is, and then directing cells in the left cerebral cortex that control movement of the right arm to send movement messages down nerves in your right arm. Through their connections to your muscles, stimulation from these nerves will cause certain muscles to contract and others to relax, thus allowing a smooth arm-raising movement. Sensors that tell the brain where various body parts of your body are (your kinesthetic sense) will confirm that your arm is raised, so even if your eyes are closed, as long as your teacher’s instructions are still in your memory, you will know it is time to execute instructions to reverse the contractions and relaxations so as to bring the arm back to its original position. Once that happens your kinesthetic sense will tell you your arm is lowered. Finally, your memory of this movement sequence will be compared to your memory of the teacher’s instructions, and when it matches you will be aware that you have behaved correctly.