Thinking And Moral Problems/1. Thinking/1. The Brain
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[edit] The Brain
The brain evolved in animals because there is a strategic advantage in being able to detect and capture food (as in say a mollosc) and later to search and find food and sexual partners. The brain is thus a mechanism for locomotion and for avoiding hazards.
The brain’s chief job therefore is to store and operate the controls that command many inherited (or instinctive) body functions. This section discusses a little of what happens during this process, so that the difference between what the brain does and what is involved when thinking can be made clearer.
Instinctive behaviours are transmitted from one generation to the next through gene codings, as has been demonstrated many times. For instance, fruit flies normally wake up with daylight, nap in the afternoon, then fall asleep at dusk. This behaviour is controlled by a gene, the so-called “period gene.” If this gene is removed from male and female flies which then mate, their descendants sleep at random times. If the gene is then returned to these time-less progeny, they and their offspring will resume regular sleep patterns.
The first, tiny part of this instinctive behaviour started as the result of a mutation [1] eons ago that caused one fly to sleep during the dark, with the concomitant reduced danger of being eaten compared to flies that were sleeping during the day. Surviving and passing this mutation to its descendants, this fly became the progenitor of successive generations that also fell asleep at dusk, so surviving in greater numbers than those lacking this [2] Jonathan Weiner provides an example[3] that nicely illustrates the value of instinctive behaviour in animals larger than fruit flies. He describes an experiment that uses a blackened piece of cardboard or wood cut into a bird-like shape. When this shape is moved in one direction across a light sky or ceiling it appears to be the silhouette of a goose flying; if it is moved in the other direction it resembles a hawk. When newly hatched goslings, raised in an incubator and having had no contact whatsoever with any adult goose, are shown the cut-out moving in the goose-resembling direction, they pay no attention. When the same cut-out is moved in the opposite direction, they scatter and attempt to hide.
Instinctive behaviours, like all others, depend upon the brain recognizing the significance of signals received from body sensors, or from the presence or absence of chemicals in body fluids. The question slowly being answered[4] is, “how does the brain know what to do when it receives such signals?” Neurons in the brain (Hercule Poirot’s “little grey cells”) hold the answer.
Most human neural cells (neurons) resemble minute, spiky blobs with tails. The blob, or body, is called the soma. The tail, a long, thin, branching, tube-like extension, is called the axon. The hundreds of short, spiky structures fringing the soma are called dendrites. When activated, electrical signals in the form of electrically charged chemical ions travel from the dendrites, through the soma, along the axon and its branches (the fanout[5]), to a number of bubble-like terminating vesicles. Ions arriving at the vesicles cause the discharge of neurotransmitter chemicals into the minute gaps that separate one neuron from another. These chemicals are detected by so-called synaptic knobs on dendrites belonging to neighbouring neurons, where they may start new ion flows within receptive neurons.
Neural networks store information for later use. This is done in a two-step process. First, flows of chemical ions circulating in tiny closed networks of neurons hold data temporarily. Much information from eyes, ears and other sense organs is temporarily stored in such neural loops while being screened for significance. Since the majority of incoming information is of little interest, most of it is discarded. (Cutting off the energizing nutrients prevents the loops from becoming significant.) Second, information having a relationship to other pre-stored or incoming data that is deemed significant can be kept active by constantly re-energizing the loops. This induces the growth of synaptic knobs on dendrites.[6] Additional synaptic knobs facilitate the transmission of neurochemicals across the dendritic gaps and thus build pathways of lowered electro-chemical resistance connecting one neuron to another. These pathways form neural networks that can retain the bytes of information that induced their formation for many years. Millions and millions of neural networks, each storing tiny bits of information, are to be found within everyone’s brain (most laid down during our first few years of life). [7]
The brain analyzes and interprets information coming from the senses[8] by routing it through earlier-formed neural networks. These respond (think “resonate”) to the presence of specific, tiny, chunks of information that match the chunks that earlier caused the network to form. This can be illustrated by electronically tracing what happens to information received by the eye, a well-explored example that helps us to understand what the brain does with data from other body sense organs. Light, reflected from the object we are looking at, enters the eye and falls upon the light-sensitive rods and cones in the eye’s retina. This creates millions of tiny signals, and these travel along the optic nerve to the brain. Key aspects of the component signal, such as information bytes denoting vertical edges, excite existing neural patterns (i.e., tiny memories) of the kinds of objects that have vertical edges. The same “analysis” is done for horizontal edges, relative sizes, colours, shapes (for instance, the vertices of any triangular aspects the object may possess), and so on.[9] This process continues until the brain excites a pattern that matches stored patterns of objects similar to the one being viewed and the object is “recognized.” “Recognition” is complete when additional characteristics, retrieved from other neural networks storing “memories,” can be added.[10]
Memories of objects and events are built up by a reverse process. Early in life, a toddler, staring at a fir tree, for example, would have stored information in his or her brain about its general shape, colour, branch pattern, leaf shape and other characteristics. Each aspect would have been broken into smaller bytes, temporarily then permanently stored and linked by neural pathways to other related bytes (including, but added much later, bytes representing the name of the tree). If more fir trees were noted, neurotransmitting chemicals would continue to induce the formation of synaptic knobs linking and reinforcing stored memories of tree parts and whole trees. Eventually, neural networks storing relatively detailed memories of fir trees would be built. Information received upon seeing a maple tree, having many similar features, would connect into many of the same neural patterns used by the fir tree memory, but would, of course, connect into other quite different ones. (At least, it would for those who had learned the difference between a fir and a maple. Those who had not discovered the similarities and differences would have to make do with a generic tree-memory.)
Whether or not any of this knowledge affects survival would be a matter of circumstance, but it is clear that memories built up through experience do greatly affect what we know,[11] as well as what we come to believe and how we behave. Much more about this later.
Information that depicts frequently seen objects travels along, and reinforces, the same neural pathways, making them evident by the thousands of synaptic knobs (as many as 10,000 or more) that form on the dendrites of neurons along these routes. Such large numbers of synaptic links vastly increase the brain’s sensitivity to similar stimuli,[12] thereby decreasing response time—an important survival feature in potentially dangerous environments. Conversely, seldom-seen objects take more mental effort and may be only slowly recognized. Because our brains can carry out many unconscious functions simultaneously, we experience signal analysis and recognition as though it happens instantaneously. However, information flow along neural axons and across synaptic gaps is slow compared to information flow in computers.
Of course, recognizing the significance of incoming stimuli involves a lot more than described above. To better appreciate how information from our senses is used within our brains, consider what must be happening if, for example, we suddenly notice that we are about to walk into the branch of a tree. Before the brain can induce any action, it must, at the very least, understand the following. First, it must understand the nature of the tree’s relationship to us (e.g., that the tree will do nothing to us if we do not bump into it). Second, the brain—as well as the mind—must have access to, and be able to use, memories of what actions have succeeded in the past (e.g., that we can avoid trouble by simply ducking our head or by stepping sideways). Third, the brain needs to be constantly aware of the body’s abilities and limitations (e.g., it must know that we can’t jump out of the way if, for example, we walk with a cane). All these things, and many more, must be known to the brain just so that it can cause the body to act in a suitable manner.
It is important to note that most of what has been described above is not thinking, for even simple life forms perform many of the same functions. They react to stimuli, and show evidence of possessing memories by using the information stored in these memories when reacting. Amoebae move away from acidic areas. Earthworms sense the void of large holes in the ground and move around them. Spiders feel their web trembling and emerge to envelop prey, and so on. All living entities respond to changes in their environment by sensing stimuli of one kind or another, then acting upon what these stimuli represent to them.[13] These sensing, analyzing and danger-avoiding activities are continually being carried out, even by primitive animals. Advanced animals have inherited these same abilities, most of which occur within the brain. But almost all of these are programmed activities which take place without any thought.[14] They form what may be considered to be a lower level of neural functioning. Although collecting, storing and recognizing signals are important and necessary functions significant to thinking (just as buying and storing tools and materials are important functions in a factory’s operation), they are not “thinking” per se. They are simply operations that trigger the release of action-inducing chemicals. In as much, these functions are similar to many others that support and maintain the body’s welfare. Section three of this chapter, First- And Second-Level Thinking, clarifies this distinction.
