Our Senses and Observation
We often speak of the power of observation. Why do we refer to observation as a power? A keen sense of the world around us was undoubtedly an essential power of our early human ancestors. Sensing or observing the world around them meant their—and our—survival. Avoiding dangerous animals, sharp objects, steep drop-offs, poisonous plants, and aggressive gestures from other humans all required observation. Even simply finding the way home demanded developed observational skills. Observing the position of distant mountains or a specific stand of trees brought our ancient ancestors back to camp.
Long before the arrival of humans on the evolutionary scene, animals evolved complex nervous systems with magnificently designed environmental receptors for things similar or identical to sight, hearing, smell, taste, and touch. The absence of these senses would leave an animal completely vulnerable and unable to cope with a challenging environment, and even animals that lack familiar sensory organs can experience their environment in crucial ways. Clams lack eyes, but can sense changes in water temperature. Their temperature sense tells them when the tide is out, allowing them to shut tightly to avoid drying out or becoming prey for a hungry passerby. Sightless amoebas “taste” or “smell”their liquid surroundings. They slowly move toward food and away from unsuitable temperatures. They ”feel” the surface they crawl upon and change direction if it’s not to their liking. The subcellular structures responsible for these amoeba responses have their counterparts in higher animals, including humans.
Compared to amoebas, humans have significantly more advanced and complex sense organs. The overall transfer of information by each of our five senses shares basic similarities. Information from the environment is gathered by specialized parts of the eyes, ears, nose, skin and tongue called receptors. Receptors in each of these parts of the body are designed to gather specific types of information from the physical world. For example, the ear is designed to respond to the vibrations generated from moving objects. These vibrations are commonly referred to as sounds. Sound travels through matter as a wave, and it is our sense of hearing and the structures of the body involved in hearing that translate a wave into recognizable sounds. The shape of the ear funnels waves produced by vibrations through the ear canal to the eardrum. The eardrum, which consists of a membrane called the tympanic membrane, is stretched tightly so that it responds with great sensitivity to the vibrations of sound waves. As the sound waves reach the eardrum, the membrane begins to vibrate. These vibrations are passed from the eardrum to the inner ear. Within the inner ear is a structure containing tiny hair cells, which move in response to the waves and trigger the generation of electrical impulses to the auditory nerve. The electrical impulses travel through the auditory nerve to the brain, where the information is processed so that we may respond to it appropriately.
Likewise, receptors in the eyes are designed to respond to electromagnetic radiation (visible light), those in the nose and tongue to specific molecules and those in the skin to temperature, pressure, and stretch. In each of these cases, the specialized sense receptors initiate an electrical impulse that travels through nerves from the eyes, nose, tongue or skin to the brain for interpretation.
As a result of the unique relationship between a sense receptor and a physical phenomenon such as vibrations or pressure, each sense provides distinctly different information or observations of the external environment. Hearing provides information about the volume and pitch of sound, sight- the color, shape and size of substances, touch- the texture and weight of objects, smell- the intensity and fragrance of odors, and taste- the sweet, salty, bitter or sour qualities of food and drinks.
Observation and Comprehension: A Human Preoccupation
What made humans so successful that we were able to dominate nearly every niche on Earth? Was it our large brains? Yes, but it’s not quite that simple. All higher animals have brains. Without them, their keen senses would be practically useless. Sense organs can only detect signals from the environment. Without a brain to interpret environmental signals, sensations would be meaningless noise with little survival value to the animal. The hawk’s eye can detect the movement of a small rabbit at an incredible distance against a landscape of similarly colored and sized objects, but it is its brain that interprets the rabbit as food. It is the dog’s brain, through information collected by its nose, eyes, and ears, that differentiates the smell, face, and voice of it’s master from all others.
While other animals rely on their brains to aid their sense organs in reacting to the environment, it is at this level - that of interpreting sensations received through our senses - that humans truly excel. This is because our brains have evolved higher levels of cognitive ability than any other animals by far. In particular, our brains have become extremely adept at processing new information and comparing it to things we have previously learned. Biologically, this has come about by the steady development of a part of our brain known as the frontal lobes. Our frontal lobes, located just above our eyebrows, coordinate information obtained by our senses and create a complex network of neural connections to allow us to see deep meaning and significance in the happenings that occur around us. Our frontal lobes have swelled over the millennia to a point where our foreheads now protrude ever forward beyond the ridges of bone that underlie our brow, giving the human silhouette its distinctive profile compared to other primates and our minds an advantage never seen on Earth before.
Another important part of our brain developed over the same period of time. This area, located above and to the front of our left ear is known as Broca’s Area. It is the part of our brain responsible for articulate speech. Using these two extraordinary brain structures, our frontal lobes and Broca’s area, has gifted us with the unprecedented ability to understand the physical world around us. We combine observation with language to communicate rationally constructed ideas to each other and to work together to solve common problems.
This combination of observation and communication has propelled our species well beyond all others in our ability to influence and control our own destiny. It has allowed us to create art, music, literature, philosophy and culture. It has given us a ceaseless curiosity and imagination. It has given us understanding and intellect. It has given us science.
We should remember the fundamental importance of our ability to observe and respond to the world around us. However, at the same time, we should never lose sight of the sheer joy humans experience in using our cognitive gifts. The thrill of discovery and the creative impulse of the human brain differentiate what we understand from that of humans of generations past and from what we can imagine of our own - and of our species' - future.