Tag: Prosopagnosia

Since it’s been a while, I’m going to rehash some ideas and then weave in few more concepts: supply chains and maps. We’re still dealing with perceptions and beliefs in all of this.

So, in a recent post, I introduced the idea that emotions and motivations might be more accurately thought of as “visceral beliefs” – a category of perception that originates within the body, and which is built up from basic processes and learned expectations. We call these things “feelings” (I feel angry. I feel hungry. I feel curious. I feel tired…). In each case there is no such thing, really, as say anger. Rather there is a perception originating in our body that we term “anger.” One thing to realize, though, is that even if “you are not feeling it,” this does not mean that your emotional machinery isn’t nonetheless whirring away and influencing your behavior. Not all perception reaches our awareness, just as not all perception is universal. The logic is the same as what is applied to “normal perception” – sight, taste, touch, and so on. So let’s remind ourselves of some of the principles underpinning “normal perception.” 

Perceptual Machinery

Psychologists long-ago established that perception isn’t a passive transcription of external sensations, but rather involves both a direct construction and an active interpretation. The result of these bottom up and top down processes gives us many of the furnishings and rooms of our psyches. The direct construction is done by the machinery at hand. We have been imbued by evolution with machinery such as rods, cones, chemical receptors, and hair cells that react to a particular range of environmental energies and that turn those inputs into patterns of neural firing. Do all animals, or individuals for that matter, use the same machinery? Of course not. Some birds possess machinery that allows them to “see” the earth’s magnetic fields. Some fish possess machinery that responds to electric fields, and honeybees can see patterns of polarized light that can be used to navigate. As Hamlet would say, “There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.” The dimensions of our perception are but a sliver of all possible dimensions, and humility (and wonder and a certain arrogance) goes hand-in-hand with doing good psychological science.

Further, even within a common assembly line of perception, e.g., vision, different tools allow organisms to handle different ranges of resources. Our own visual system cannot “handle” electromagnetic spectra from the ultraviolet bands, but honeybees would respond to management’s request to process UV light with “bring it on.” For honeybees ultraviolet inputs are part of their normal experience, while longer wavelengths (i.e., the color “red”) are not (see page 138 of provided link).

To use a crude metaphor, the machinery of perception is like a supply chain that assembles the lived-in environment of the psyche. Depending on the desired product, different supply chains make use of different resources. The supply chain for a rocking chair is quite different from the supply chain for an iPhone. Similarly, the supply chain for a melody will differ from one that produces the smell of cinnamon. 

Supply Chains and Perception

Let’s go ahead and push this analogy between supply chains and perception because it will allow us to intuit some general principles of perception. 

Here is a map of the supply chain for the Jansport Big Student Backpack. Be sure to click through to the original site, because each of the nodes can be clicked on for further information about the specific factories. Among other things, in this visualization we learn that there is a thread supplier in Malaysia, a yarn manufacturer in India, dying facilities in Thailand, rubber, zipper and yarn facilities in China and Taiwan, and an assembly facility in Indonesia that puts together the final backpack (along with many other products such as shoes, windbreakers, umbrellas, etc.) before shipping it to a primary distribution center in California. This distribution center then introduces the backpack into consumer awareness by placing it on the racks of a store or in the pages of a catalog. The consumer “sees” the final backpack, not the undergirding supply chain that makes the backpack possible.

Our own perception works according to similar principles. Dedicated areas of the brain specialize in “producing” vertical lines, horizontal lines, colors, visual movement… , and yet other areas receive these inputs and assemble them into larger products. At some point these perceptual products enter our awareness, but there is a considerable amount of assembly and processing that has already happened prior to this point. Below, for example, is a crude diagram showing the “supply chain” for visual information in Homo sapiens. Interrupt that supply chain at different locations and particular visual goods will no longer be available.

Prosopagnosia, for example, is a phenomenon in which individuals lose the ability to “see” faces (click here to read an article about potential treatments). prósōpon = face, a = not, and gnosis = knowledge. Prosopagnosia usually results from damage or congenital alterations to a brain region known as the fusiform gyrus.  Individuals with prosopagnosia might be able to describe the components of a face just fine: the nose is bulbous, the eyes are brown, the hair is curly and black. However, despite possessing the components of a face, they simply don’t possess the ability assemble those components into a face.

The condition known as blindsight also illustrates how disruptions in the visual “supply chain” are not an all-or-nothing thing. Blindsight is characterized by a functional blindness in which individuals nonetheless possess abilities that are dependent on vision. (If you have access to online articles, here is one that provides a nice overview and here is another.) An individual with blindsight might not be able to see a baseball, but could potentially catch one tossed their way. They might not consciously know that an object is present, but nonetheless could correctly guess as to the direction of its movement. In general the reason for the blindness of blindsight involves damage to area V1 of the visual cortex. This is an area at the back of the brain that receives the bulk of input from our retinas. However, as the figure above shows, several inputs from our retinas are sent in parallel to other brain regions (the superior colliculus and the lateral geniculate). It is thought that these inputs allow for the “sight” of blindsight. Conceptually, though, we can think of this with reference to our supply chain analogy. If we lose our “distribution center” or our “assembly factory” certain types of perception might never reach our awareness. Nonetheless, this does not stop the thread, zipper, or fabric dying factories from producing their goods – goods that can be used in other supply chains, as needed.

Issues in supply chains don’t only have to do with the loss of resources such as we “see” in individuals with blindsight or prosopagnosia. For example, what would happen if a supply chain began to include inputs of colored fabric to an assembly factory that normally only received black fabric? We might end up with rainbow colored backpacks! Synthesia resembles just such an outcome. This syndrome refers to a phenomenon in which some individuals experience the stimulation of multiple sensory pathways when only a single pathway is objectively stimulated. Numbers and sounds might be “seen” to have particular colors; observing another individual’s hand being touched, might produce a sensation of touch in the observer. It should be noted that synesthesia is not an imagined or arbitrarily conjured sensation. Rather, the synesthete simply and consistently perceives a mixed sensory experience relative to what others experience. 

I don’t want to push the analogy between the machinery of perception and supply chains too far. After all, it’s just an analogy. Computers aren’t the same things as brains and supply chains are not the same thing as perception. However, there’s one more point I’d like to squeeze out of the supply chain / perception analogy, and that’s the concern with balancing resilience and efficiency. 

Efficiency, blooming and pruning

A central issue faced by the management of supply chains involves balancing efficiency and resilience. For example, the coronavirus outbreak has made news for disrupting supply chains through China, and many green technologies currently face vulnerabilities in their supply chains that might affect their ability to scale up. In order to handle these issues capable managers need constantly to grow and prune their supply chains in ways that minimize costs while maximizing resilience. Extra supplies need to be maintained, backup factories need to be kept at the ready, and of course all of these contingency plans impose costs. If the world were perfectly predictable, these costs would be unnecessary. But the world is not predictable. Storms, viruses, political unrest, new technologies and competitors all impose costs. Such is life.

Perhaps not surprisingly, the machinery of perception deals with similar demands for resilience and efficiency, and the way that our brains manage these demands shapes the environs of our individual psyches. For example, the development of our brains is characterized by an overproduction of connections, followed by a pruning of these connections. This “blooming and pruning” occurs in different areas of the brain at different times in our lives. Below, for example, is a figure showing the approximate developmental time course for several brain regions along with their hypothesized functions. What it shows is that our visual and auditory “supply chains” are crudely mapped out with a hodgepodge of connections that are then tightened up over the first three years of life. Areas involved in speech production, on the other hand, have a later “blooming” that is followed up by a pruning that occurs until approximately age 7. [Remember: these are averages and say nothing about what is happening in the brain for any single individual.] 

The pruning of pathways in our brains is crudely guided by a “use it, or lose it” maxim. Connections that are repeatedly stimulated are strengthened and maintained, while those that are rarely stimulated are deleted.  The result is that our perceptual supply chains are made more efficient at delivering the products that we apparently need. If you do not need to distinguish between “l” and “r” sounds, then your brain will eliminate the wasted circuitry that produces the perception of these two distinct sounds. Simultaneously we become worse / better at associating particular lip movements with particular sounds. Similarly, as I brought up in another blog post, if you do not need to distinguish between faces that have particular racial characteristics, then your brain will eliminate the “wasted” circuitry that produces the perception of these differences. In extreme cases, experimenters have even been able to create environments in which animals lose the ability to perceive horizontal or vertical lines. Again, use it or lose it. If the world does not need you to “see” vertical lines, then your brain is not going to waste the supply lines necessary to create a perception of vertical lines. In psychology this phenomemon is termed perceptual narrowing and it is the result of synaptic pruning , but conceptually perceptual narrowing and synaptic pruning are no different from what supply chain managers do every day. 

Summing up the Supply Chain / Perception Analogy

All right, the main principles to draw from our analogy between supply chains and perception are:

• Just as supply chains construct products by integrating and orchestrating a network or factories, the machinery of perception constructs our psychological world from many distributed areas in the brain.

• Just as a zipper or yarn factory can help in the assembly of many different goods, perceptual “factories” can provide outputs that are used for many different types of percepts (e.g., faces, objects, animals, etc.).

• Just as much of a supply chain is invisible to the consumer, much of the machinery of perception is invisible to our consciousness.

• Just as supply chains are molded by concerns for efficiency and resilience, our brains mold the machinery of perception by balancing physiological costs and environmental demands.