Sensation is the information the brain receives; perception is the result of the brain selecting, organizing, and interpreting this information. We don’t experience the sensory data directly; we experience the result of the brain’s processing of it.
As an aside, some people consider sensation to be a physical process, while perception is a psychological process. We may talk about and think about the physical and the psychological as being two distinct domains, but the brain that receives sensory data also does the interpreting that gives rise to perception. It doesn’t make a distinction between the physiological and the psychological in this or in any other regard.
An example of the difference between sensation and perception is prosopagnocia, a neurological disorder experienced by about one in 50 people, including neuroscientist Oliver Sacks. More commonly known as face blindness, it’s the inability to recognize faces, including one’s own in a mirror. Prosopagnocia is not a result of memory dysfunction or loss, impaired vision, or learning disabilities. The sensory data is input, so to speak, but the brain can’t interpret it so there is no perception.
While an interpretation—anyone’s, of anything—can be more or less accurate, it is always approximate. As Daniel Gilbert said, there isn’t a view from nowhere. All interpretations are based in a point of view from a particular brain at a particular point in time, so interpretations are inherently limited and slanted—and they vary both from individual to individual and within individuals at different times and under different circumstances.
“Normal” vs “Abnormal”
We tend to think that there is always a correct interpretation (perception) of an object or an event—that objects and events and their properties exist in an immutable state independent of us. And if we apply the appropriate lens, we believe we can achieve complete, or nearly complete, accuracy in our perception. At the same time, we tend to assume (operate as if) we are perceiving correctly.
So it’s tempting, not to mention less troublesome, to view others’ experiences or perceptions—especially when they don’t match ours—as missing the mark somehow. There’s an error in their, or their brain’s, calculations. One example is color blindness (also called color deficiency—see what I mean?), which has a genetic basis. Another example is tone deafness. There are many more, including:
- Aphantasia: the inability to create a visual mental image of something that isn’t present.
- Synesthesia: a sort of mixing up of sensory pathways in the brain (experiencing letters of the alphabet as having colors or associating a smell with a word).
- Misophonia (aka soft sound sensitivity): a disorder in which certain repetitive sounds like gum chewing or paper crinkling automatically trigger powerful negative emotional responses.
And don’t forget prosopagnocia.
Clearly color blindness, aphantasia, synesthesia, misophonia, and other such conditions provide individuals with different experiences of reality than we might consider the norm. But does it make sense to say it’s wrong to experience the letter “M” as orange or the color green as smelling like cilantro? Richard Feynman had synesthesia and saw his equations in colors. Far from being wrong, this sounds pretty great to me, although that’s coming from a point of view of not having the experience.
Is there something wrong with that fellow over there who can’t mentally visualize a field of poppies or fluorescent purple mushrooms or a galloping horse? Aphantasia, unlike synesthesia, seems tragic to me; I can’t imagine I would be the same person if I didn’t have the vivid visual imagination I have. But how could one miss it if they never had it to begin with?
Is it wrong that the crinkling of paper or chewing of gum elicits a fight or flight response in that woman seated the next row over on the plane? She just seems to be overreacting and behaving rudely. Misophonia doesn’t seem desirable to me in any way. Of the few conditions I’ve included here, it’s the one that people who have it are perhaps most likely to view as being abnormal. That’s because it can cause problems beyond the purely sensory. It can create a lot of stress in personal relationships or interactions and in social settings. Many sufferers and the people they interact with tend to think it’s a psychological problem, meaning they could control their response if they tried harder. Or they need therapy. Nevertheless, it is an example of the brain sensing and perceiving (interpreting) sensory data and providing a resulting experience. It’s no different from any other instance of sensory processing.
External vs. Internal
The conditions described above all relate to the processing, interpretation, and experiencing of external sensory data. Enough research has been done on how the brain processes external sensory data to allow scientists to map the parts of the brain associated with them.
But there’s still much to learn about how the brain processes internal sensory information. How does it sense and organize feedback from internal organs to regulate hunger, satiation, thirst, nausea, pain, breathing, heart rate, blood pressure, etc.?
Scientists think that internal sensing may be more complicated than external sensing because, according to cell biologist Chen Ran:
[I]nternal organs convey information through mechanical forces, hormones, nutrients, toxins, temperature, and more—each of which can act on multiple organs and translate into multiple physiological responses. Mechanical stretch, for example, signals the need to urinate when it occurs in the bladder, but translates into satiation when it happens in the stomach and triggers a reflex to stop inhalation in the lungs.
How does the brain determine (interpret) sensory data so that we have an accurate enough experience to allow us to respond appropriately? Researchers do have some leads they’re following as they attempt to get a handle on the coding of internal senses throughout the brain. One motivation for this area of study concerns treatment for diseases that arise from internal sensory system malfunctions—i.e. abnormal feedback.
Of course this is a bit oversimplified since this so-called feedback involves sensation, perception, and interpretation. Feedback might relate to external or internal sensory data or what we think of physiological or psychological sensory data. No matter what it relates to, however, there’s feedback that occurs at the unconscious level and feedback that we are aware of at the conscious level. Most feedback occurs at the unconscious level and doesn’t make it into conscious awareness.
What We’re Aware of
When feedback does make it into conscious awareness, we have thoughts about it (our interpretation, usually in the form of an explanation).
We also experience an emotion, which neuroscientist Antonio Damasio would refer to as a homeostatic indicator. Emotions constitute a sort of personalized, constantly updated, running report to consciousness, indicating the status quo of the organism—as the brain sees it—both internally and externally. This is pretty damn amazing, when you think about it.
If the interpreter (see last post) is like a play-by-play announcer calling a game (your life) over the radio, emotion is your response to what you perceive to be happening both on the field (externally) and internally. There’s lots of information available to you. Are you tuned in?
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