The only way individuals know anything about the world is through thoughts and perceptions. The only way science can progress is if a group of minds agrees on specific perceptions, as well as its analyses of them. But what is a perception?
Despite multitudes of neuroscientists researching for generations, no one knows what the mind is. No one can explain subjective experience, and it is still not clear what a perception is or how it forms.
LIMITATIONS OF SENSORY INFORMATION
Perceptions are based on incoming sensory data, the scenes that are created from this data, and the mental/brain production of a percept. We tend to think that what we see is reality. But there are great limitations to what we learn through our senses.
One of them is that all senses only respond to a narrow range of wavelengths of the available information. Many other factors limit each sense, and there are senses humans don’t have.
For vision, 100-rod cells are connected with one neuron, missing much detail in peripheral vision. In central vision, each cone stimulates one neuron, but these cells are refreshed often and therefore miss detail. Most of the eye’s data are filtered out, never reaching the cortex. Although we think we see everything, our minds embellish each scene.
Visual signals are first filtered for acute dangers, enabling an immediate flinch response. In the cortex, these signals mingle with those from other senses, thoughts, and emotions. There are actually more signals coming from the cortex to direct and analyze visual information than there are sensory signals. These are referred to as top-down and bottom-up signals.
All senses have similar limitations — only responding to a narrow range of data and having more top-down neurons. The cortex massages the data and fills in the gaps in all of the senses to determine perception.
Animals perceive other narrow ranges than humans, and some have unique senses. Therefore, animals have different types of perceptions and intelligence. Mice and dogs pick up vastly more information about smell than humans. In fact, even in humans there is 30 percent variability in olfactory receptors between any two individuals leading to great differences between them as well.
Although hard to define, perceptions are critically important because they help create models for us to use in making decisions about our actions.
Recent studies show that perception of social experiences dramatically affects genetic networks and the immune system. Loneliness causes immune alterations, increasing inflammation, and decreasing defenses against viruses. But it is the perception of the loneliness that has this effect and not the external events themselves. People isolated or imprisoned do not experience it if they are mentally close to someone.
Another immune effect involves the perception of happiness that comes from engaging with our communities. Happiness from community service decreases inflammation factors and increases anti-viral factors. Surprisingly, other forms of happiness do not do this — such as material possessions and travel.
TOP-DOWN VERSUS BOTTOM-UP
There are a wide variety of experiments that show the top-down effects of our perceptions. In one, a picture of a bright light (without actual physical brightness) causes the pupils to react as if it were real brightness. In another, if hungry, people see words related to foods more clearly and as if they are brighter. Poor children see coins as larger than they are. People holding guns perceive others holding guns although they aren’t. People with broad shoulders see doorways as narrower in absolute measurement. Better baseball hitters see the ball as larger.
There are other top-down effects from words and thoughts influencing sensory data. When hearing “She kicked the ball,” the brain centers related to kicking are stimulated. Metaphors, such as “soft-hearted” and “wet behind the ears” trigger both brain language regions and the specific sensory regions of the heart, wetness, and ears. When abstract concepts such as a good deed are recalled, surroundings are viewed as visually brighter. Recalling an unethical deed has the opposite effect. When reading fiction, the brain’s sensory and motor regions are active as if the reader is actually experiencing the events.
WHAT DO WE PICK UP?
In a famous experiment, subjects are told to carefully observe a staged event. Then a man in a gorilla suit walks across the stage, bows, and walks off. Almost no one notices it, because they are focusing on something else and not expecting it. A more recent version of this experiment involves radiologists reading MRI film, who do not see a large gorilla imprinted in the film. No one expects a gorilla to be in an MRI. Other experiments also show that we see only what we are prepared to see.