The outputs of the body include mechanical movements, radiant heat, sounds, minute electrical signals, as well as excretions and secretions that serve various biological functions. Some of these may serve as communication signals at a basic biological level, but verbal communication provides the greatest insights into the mind.
The skin is covered with many specialized glands that secrete sweat, sebum, smegma, and earwax. In addition there are glands that produce tears, saliva and milk. Sweat serves primarily to cool the body. However, the sweat of the underarms develops a strong smell when it ferments under bacterial action. Scientists have debated whether sweaty smell is supposed to be an attractant, a repellent, an indication of vigor, or serves other functions. The widespread use of antiperspirants and air conditioning has virtually eliminated this type of stimulus from our society. However, researchers at the University of California at Berkeley conducted an experiment where women sniffed a bottle containing androstadienone, a chemical found in male sweat that smells vaguely musky. Tests showed that the blood pressure, heart rate, breathing, and levels of cortisol in the women increased within 15 minutes of sniffing the chemical and remained elevated for more than an hour. The women also reported elevated mood and sexual arousal. Sebum and smegma are oily secretions that lubricate various parts of the body. They also have characteristic smells at close range to the body. The pubic area has a musky smell that may play a role in sexual stimulation.
Excretions like urine and feces serve to carry away waste products of the body, but they also carry a lot of information about the body. From a sample of urine it is possible to determine the function of the kidneys, the presence of venereal or parasitic diseases, and whether a woman is pregnant. Feces can be used to identify dietary components, parasitic infections, the presence of ulcers, and many digestive functions. Menstrual fluids and semen are excretions of the body that are part of the reproductive cycle, but which can transmit disease-causing organisms from infected individuals.
Exhaling, sneezing, coughing, burping, and intestinal gases are all outputs of the body that give information about the body. A sigh is a form of exhaling that may indicate weariness or relief. Sneezing and coughing are used to dislodge obstructions in the respiratory passages or as a reaction to irritants. The air expelled during coughing and sneezing may carry bacteria and viruses in droplets of mucus and saliva. Burping and intestinal gases are products of fermentation and digestion that may have offensive smells. The smell of the breath may indicate diet, food residues, the presence of caries, and smoking habits. The smell of a woman's breath changes during menstruation.
Many diseases can be identified by the odors emanating from the body. In the days when house calls were common, doctors were advised to blow their nose to increase their olfactory sensitivity before going into the room with the sick patient. Bacterial colonies of Pseudomonas have a grape-like smell, whereas colonies of Proteus have a burned horn smell.
The body generally maintains a temperature of 37° Celsius (98.6° Fahrenheit). The testicles require lower temperatures for sperm production. Fever is a pathological condition where an abnormally high body temperature is sustained. Temperatures higher than 42.5° C (108° F) kill human cells.
The electrical signals in the brain are in the order of 100 microvolts, that is about fifteen thousand times smaller than an ordinary flashlight battery. These signals have wave frequencies of between 1 and about 20 Hertz (or cycles per second). The electrical signals in the heart are around 1 millivolt, ten times stronger than those of the brain, but still very small and impossible to detect outside the human body except through great amplification. By contrast, electric eels have special nerve endings that enable them to generate from 200 to 600 volts, enough to electrocute a person. The neurons of the human brain have been estimated to generate about 25 watts of power.
The position of the body can indicate aggression, fear, or a whole spectrum of human attitudes. Crossed arms tend to indicate a reserved attitude or closed-mindedness, a slouch indicates disdain or carelessness, sweaty palms indicate nervousness, a weak handshake means lack of confidence, and a pale face or trembling are synonymous with fear. Facial expressions are produced by movements of the eyes, eyebrows, nose and mouth. Narrow eyes mean anger and widened eyes indicate surprise. A frown denotes concern, and pupils expand when something is of interest. A mouth with down-turned corners is sad; one with up-turned corners is a happy smile. Happiness, sadness, fear, anger, surprise, and disgust are facial emotions that are widely recognized around the world regardless of culture. These facial expressions are made with five facial muscles.
The attire and hair styles that we wear also send messages which can be part of body language. Purple-dyed hair and body piercing indicate non-conformity, pin-striped suits just the opposite. Expensive jewelry, cosmetics, and perfume send a message of affluence. Beards, wigs, clothing, and cosmetics are all used to decorate our bodies to send conscious or subconscious messages to on-lookers.
Coughing, sneezing, breathing, and heartbeats are sounds output by the body. There are also mechanical noises such as clapping and whistling, but by far, the most important sounds are produced through singing and verbal communication.
As was mentioned in the previous chapter, verbal communication is more than just sounds. Words convey mental images to our listeners. What we say or what we imply changes the listener. The way in which we say something also carries a message. The use of a rich vocabulary may imply wisdom or snobbishness, forcefulness indicates conviction, and hesitation represents insecurity.
Songs and rhymes are special forms of ritualized communication. Before writing was invented, oral history was the only way to pass information from one generation to the next. Poems and songs were particularly effective at passing information, because they could be learned at an early age, even though they might not be understood until much later.
Memes are ideas or behaviors that can be passed from one person to another by learning or imitation. A culture may be defined as a collection of memes which enable individuals to function within the society. Examples of memes include beliefs, gestures, practices, fashions, habits, songs, and dances. Successful memes propagate themselves and are adopted by the members of a society because they provide a benefit or enable survival. Simple traditions like washing the hands before eating, or the Oriental custom of taking off the shoes before going inside a house promote cleanliness and reduce the rate of infections. People who do not follow these practices will get sick more often or perhaps die from poor sanitation. Thus, the cleanliness meme provides tangible benefits.
The material inputs into the body are food, drink and air. The chemical components of food and drink are proteins, fats, carbohydrates and water. The material outputs of the body are feces, urine, sweat and carbon dioxide. Feces consists of undigested food. The kidneys are responsible for excreting urine which is mostly water and two nitrogen-containing substances: uric acid produced from nucleic acid metabolism, and urea produced from protein metabolism. Sweat is mostly water with some electrolytes (mostly sodium chloride). Respiration is responsible for burning carbohydrates, fats, and proteins to produce carbon dioxide. Body weight is lost by the output of carbon dioxide through the lungs, one breath at a time. Exercise increases the output of carbon dioxide and accelerates weight loss.